# OpenGL or pure SDL gfx?

**URL:** <https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341>\
**Category:** SDL Development\
**Created:** [September 14, 2003, 2:57pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341 "2003-09-14T14:57:01Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![Henning](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/h/ecae2f/32.png) [@Henning](https://discourse.libsdl.org/u/Henning)\
**Post date:** [September 14, 2003, 2:57pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/1 "2003-09-14T14:57:01Z")

</div>

Still working on my “game”.

I want it to be just a 2D game, but with a scrolling background. I’ve read a lot about SDL and GL and linux game programming in general now, and I’m still not able to get really smooth scrolling without resorting to openGL (I guess it has to do with GL supporting my hardware while SDL does not?). But I don’t really want any 3d effects or anything, so I think it’s perhaps a little “overkill” to use GL just to get smoother scrolling (also I’m puzzled by the fact that my 1,5ghz PC can’t produce smooth scrolling, when it was not much of a problem on one of those good ol 7,14mhz (iirc) computers).

What do you think? Is it normal to use GL for the gfx part, even when the game is not 3d? Sounds a little weird to me, but who knows. For now it seems to be the only way to get some hw supported scrolling.

Regards  
Henning

---

<div class="post-metadata">

**Author:** ![Olof\_Bjarnason](https://discourse.libsdl.org/user_avatar/discourse.libsdl.org/olof_bjarnason/32/256_2.png) [@Olof\_Bjarnason](https://discourse.libsdl.org/u/Olof_Bjarnason)\
**Post date:** [September 14, 2003, 3:27pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/2 "2003-09-14T15:27:01Z")

</div>

I think you loose little in using OpenGL for your 2d game.

That is what I am using in my 2d project Kung Fu Kitsch, and I think  
lots of linux 2d games do so too.

And you get some additional things free with the SDL/OpenGL  
combination:

- OpenGL is h/w more often than standard SDL-blitting
- OpenGL may rotate any sprite for free
- It’s good know-how in computer graphics in general
- SDL has an active community and lots of games  
use it, and this mailing list is really great

Anyway, I can’t see why you’re not able to do smooth scrolling on you  
machine using SDL-blitting… even if it is software it should be  
smooth.

/Olof

### Henning: “[SDL] OpenGL or pure SDL gfx?” (2003-09-14 23:55)

#Still working on my “game”.#  
#I want it to be just a 2D game, but with a scrolling background. I’ve read a lot about SDL and GL and linux game programming in general now, and I’m still not able to get really smooth scrolling without resorting to openGL (I guess it has to do with GL supporting my hardware while SDL does not?). But I don’t really want any 3d effects or anything, so I think it’s perhaps a little “overkill” to use GL just to get smoother scrolling (also I’m puzzled by the fact that my 1,5ghz PC can’t produce smooth scrolling, when it was not much of a problem on one of those good ol 7,14mhz (iirc) computers).

# 

#What do you think? Is it normal to use GL for the gfx part, even when the game is not 3d? Sounds a little weird to me, but who knows. For now it seems to be the only way to get some hw supported scrolling.

# 

#Regards  
#Henning

# 

#\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_  
#SDL mailing list  
#SDL at [libsdl.org](http://libsdl.org)  
#[http://www.libsdl.org/mailman/listinfo/sdl](http://www.libsdl.org/mailman/listinfo/sdl)

#

---

<div class="post-metadata">

**Author:** ![Paulo\_Vinicius\_Wolsk](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/p/5fc32e/32.png) [@Paulo\_Vinicius\_Wolsk](https://discourse.libsdl.org/u/Paulo_Vinicius_Wolsk)\
**Post date:** [September 14, 2003, 3:30pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/3 "2003-09-14T15:30:01Z")

</div>

Henning, just to know, are you using software or hardware surfaces?  
I was able to get about 70fps on a Celeron 300 with an accelerated  
video card (i think it was an ATI video card), all using only SDL  
harware surfaces with RLE acceleration for colorkey based blits. With  
software surfaces I could get about 60fps on a Athlon XP+ processor,  
which is smooth for 2D scrolling. And m y game was running at 640x480  
with 32bpp.

```
However, when I ported the game to MAC OS X I had some performance 

```

problems with hardware surfaces, the blits are not that much  
accelerated on that platafform due to the way Quartz handle video  
operations (I got about 30fps when connected to the power adpter, ie,  
processor at full speed).

```
At that point I changed to Open GL and after that, the game can 

```

achieve about 300fps on my iBook 900 on energy saving mode when I turn  
off my frame control (and I have an abusive number of objects on  
screen). By these figures you can say that it’s worth to change to Open  
GL, also you have some freebies:

```
- Fast zoom and roration
- Hardware alpha blits
- You can try some cool 3D effects to blend in your 2D game

The only con: if the target computer does not support Open GL by 

```

harware, your game will suck big time. But as it’s quite difficult to  
find a gamer that does not have accelerated video cards these days, you  
can forget it.

```
I would say for you to go for it, it's worth, it may change some ways 

```

you handle things in your game, but overall it will be much faster.

```
PauloEm Sunday, 14, September, 2003, ?s 05:55 PM, Henning escreveu:

```

> Still working on my “game”.
> 
> I want it to be just a 2D game, but with a scrolling background. I’ve  
> read a lot about SDL and GL and linux game programming in general now,  
> and I’m still not able to get really smooth scrolling without  
> resorting to openGL (I guess it has to do with GL supporting my  
> hardware while SDL does not?). But I don’t really want any 3d effects  
> or anything, so I think it’s perhaps a little “overkill” to use GL  
> just to get smoother scrolling (also I’m puzzled by the fact that my  
> 1,5ghz PC can’t produce smooth scrolling, when it was not much of a  
> problem on one of those good ol 7,14mhz (iirc) computers).
> 
> What do you think? Is it normal to use GL for the gfx part, even when  
> the game is not 3d? Sounds a little weird to me, but who knows. For  
> now it seems to be the only way to get some hw supported scrolling.
> 
> Regards  
> Henning
> 
> * * *
> 
> SDL mailing list  
> SDL at [libsdl.org](http://libsdl.org)  
> [http://www.libsdl.org/mailman/listinfo/sdl](http://www.libsdl.org/mailman/listinfo/sdl)

---

<div class="post-metadata">

**Author:** ![Bob\_Pendleton](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/b/9de053/32.png) [@Bob\_Pendleton](https://discourse.libsdl.org/u/Bob_Pendleton)\
**Post date:** [September 14, 2003, 3:35pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/4 "2003-09-14T15:35:01Z")

</div>

> Still working on my “game”.
> 
> I want it to be just a 2D game, but with a scrolling background. I’ve read a lot about SDL and GL and linux game programming in general now, and I’m still not able to get really smooth scrolling without resorting to openGL (I guess it has to do with GL supporting my hardware while SDL does not?). But I don’t really want any 3d effects or anything, so I think it’s perhaps a little “overkill” to use GL just to get smoother scrolling (also I’m puzzled by the fact that my 1,5ghz PC can’t produce smooth scrolling, when it was not much of a problem on one of those good ol 7,14mhz (iirc) computers).

There is nothing weird, wrong, or “over kill” about using OpenGL to  
write a 2D game. If it is the only way to get access to hardware  
graphics then it is the only way. So, use it.

The bit about the difference in performance between an original 4Mhz PC  
and a 1.5Ghz modern PC is a complete red herring. The volume of data you  
have to move around on a modern PC huge compared to what we dealt with  
on the original PC. Not to mention that we used lots of tricks, were the  
only task running on the PC, and manipulated the hardware directly. Now  
days you are never the only process running, can’t use any of the same  
tricks, but we have astoundingly better hardware. So, if you use the  
hardware you can get the effect of what you want. Though, true perfectly  
timed smooth scrolling really isn’t possible anymore.

> What do you think? Is it normal to use GL for the gfx part, even when the game is not 3d? Sounds a little weird to me, but who knows. For now it seems to be the only way to get some hw supported scrolling.

Use OpenGL. It works.

```
	Bob PendletonOn Sun, 2003-09-14 at 16:55, Henning wrote:

```

> Regards  
> Henning
> 
> * * *
> 
> SDL mailing list  
> SDL at [libsdl.org](http://libsdl.org)  
> [http://www.libsdl.org/mailman/listinfo/sdl](http://www.libsdl.org/mailman/listinfo/sdl)  
> –  
> ±----------------------------------+

- Bob Pendleton: independent writer +
- and programmer. +
- email: Bob at [Pendleton.com](http://Pendleton.com) +
- web: [www.GameProgrammer.com](http://www.GameProgrammer.com) +  
±----------------------------------+

---

<div class="post-metadata">

**Author:** ![atrix2](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/a/a9a28c/32.png) [@atrix2](https://discourse.libsdl.org/u/atrix2)\
**Post date:** [September 14, 2003, 3:42pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/5 "2003-09-14T15:42:01Z")

</div>

Listen to bob!

Not sure if you know this but you can set “Orthographic” mode in OpenGL  
where when you draw its 2d, so its not too wierd, plus if its faster, why  
not?\> ----- Original Message -----

> From: [bob@pendleton.com](mailto:bob@pendleton.com) (Bob Pendleton)  
> To: “SDL Mailing List”   
> Sent: Sunday, September 14, 2003 3:34 PM  
> Subject: Re: [SDL] OpenGL or pure SDL gfx?
> 
> > On Sun, 2003-09-14 at 16:55, Henning wrote:
> > 
> > > Still working on my “game”.
> > > 
> > > I want it to be just a 2D game, but with a scrolling background. I’ve  
> > > read a lot about SDL and GL and linux game programming in general now, and  
> > > I’m still not able to get really smooth scrolling without resorting to  
> > > openGL (I guess it has to do with GL supporting my hardware while SDL does  
> > > not?). But I don’t really want any 3d effects or anything, so I think it’s  
> > > perhaps a little “overkill” to use GL just to get smoother scrolling (also  
> > > I’m puzzled by the fact that my 1,5ghz PC can’t produce smooth scrolling,  
> > > when it was not much of a problem on one of those good ol 7,14mhz (iirc)  
> > > computers).
> > 
> > There is nothing weird, wrong, or “over kill” about using OpenGL to  
> > write a 2D game. If it is the only way to get access to hardware  
> > graphics then it is the only way. So, use it.
> > 
> > The bit about the difference in performance between an original 4Mhz PC  
> > and a 1.5Ghz modern PC is a complete red herring. The volume of data you  
> > have to move around on a modern PC huge compared to what we dealt with  
> > on the original PC. Not to mention that we used lots of tricks, were the  
> > only task running on the PC, and manipulated the hardware directly. Now  
> > days you are never the only process running, can’t use any of the same  
> > tricks, but we have astoundingly better hardware. So, if you use the  
> > hardware you can get the effect of what you want. Though, true perfectly  
> > timed smooth scrolling really isn’t possible anymore.
> > 
> > > What do you think? Is it normal to use GL for the gfx part, even when  
> > > the game is not 3d? Sounds a little weird to me, but who knows. For now it  
> > > seems to be the only way to get some hw supported scrolling.
> > 
> > Use OpenGL. It works.
> > 
> > Bob Pendleton
> > 
> > > Regards  
> > > Henning
> > > 
> > > * * *
> > > 
> > > SDL mailing list  
> > > SDL at [libsdl.org](http://libsdl.org)  
> > > [http://www.libsdl.org/mailman/listinfo/sdl](http://www.libsdl.org/mailman/listinfo/sdl)  
> > > –  
> > > ±----------------------------------+
> > 
> > - Bob Pendleton: independent writer +
> > - and programmer. +
> > - email: Bob at [Pendleton.com](http://Pendleton.com) +
> > - web: [www.GameProgrammer.com](http://www.GameProgrammer.com) +  
> > ±----------------------------------+
> > 
> > * * *
> > 
> > SDL mailing list  
> > SDL at [libsdl.org](http://libsdl.org)  
> > [http://www.libsdl.org/mailman/listinfo/sdl](http://www.libsdl.org/mailman/listinfo/sdl)

---

<div class="post-metadata">

**Author:** ![Glenn\_Maynard](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/g/bcef8e/32.png) [@Glenn\_Maynard](https://discourse.libsdl.org/u/Glenn_Maynard)\
**Post date:** [September 14, 2003, 5:49pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/6 "2003-09-14T17:49:02Z")

</div>

StepMania is a good example of what can be done with OpenGL for a  
primarily 2D game. Give the current alpha 4 a shot (pardon the plug):

[StepMania - Browse Files at SourceForge.net](http://sourceforge.net/project/showfiles.php?group_id=37892)

You won’t be able to play the game without some music files, but  
the rest of the interface shows off lots of very smooth scrolling,  
even with a extra passes for sprite drop shadows and other effects.

OpenGL introduces its own fair set of compatibility issues, of course–but  
you get that in any accelerated API.

(Note that only the Windows end is mature; the \*nix and Mac ports are  
fairly new. Apologies that there’s no source link for the snapshot; that  
will be corrected in the next snapshot.)On Sun, Sep 14, 2003 at 11:55:26PM +0200, Henning wrote:

> What do you think? Is it normal to use GL for the gfx part, even when the game is not 3d? Sounds a little weird to me, but who knows. For now it seems to be the only way to get some hw supported scrolling.

–  
Glenn Maynard

---

<div class="post-metadata">

**Author:** ![Henning](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/h/ecae2f/32.png) [@Henning](https://discourse.libsdl.org/u/Henning)\
**Post date:** [September 15, 2003, 4:27am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/7 "2003-09-15T04:27:01Z")

</div>

> ```
> Henning, just to know, are you using software or hardware surfaces? 
> 
> ```

It makes no difference on the performance, so I’m pretty sure I only have a software surface, even when I try to get a hw surface.

> get about 70fps on a Celeron 300 with an accelerated

It’s not really the framerate that’s bad, it seems okay and above 50, but the quality of the scrolling is not good. I have tried downloading other games that use SDL, and they display about the same bad scrolling.  
It’s not a _big_ problem, it’s just that I have seen scrolling with GL, and that looks great. So I wondered if I wanted to make the change to get that kind of scrolling.

> video card (i think it was an ATI video card), all using only SDL  
> harware surfaces with RLE acceleration for colorkey based blits. With

I have tried with RLE acc. and hw-surfaces and double buffering. I used the DisplayFormat which helps a little, but still not enough.

Anyway, I think you’ve convinced me to go for GL. Which means I’ll have to go get some tutorial on that too. Oh, so much reading to do…

Regards  
Henning

---

<div class="post-metadata">

**Author:** ![Thomas\_Eder](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/t/d78d45/32.png) [@Thomas\_Eder](https://discourse.libsdl.org/u/Thomas_Eder)\
**Post date:** [September 15, 2003, 5:11am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/8 "2003-09-15T05:11:00Z")

</div>

IMHO its overkill to use OpenGL for a simple 2D game.

As noted previously you would restrict your audience mainly  
to people with hw-accelerated opengl-supported systems.

And I dont think that this kind of people will play your 2D game  
very long, because they maybe have lot of other real cool 3D games.

IMHO the audience for simple 2D games are for example children  
(and their parents who have to buy the game…).

So to buy and play a simple game for their kids, they wuold have to  
provide a hw-accel opengl system…  
In my eyes an unnecessary additional restriction…

Its possible to write a soft-scroller without opengl. Maybe there is something  
completely wrong in your main game loop or your understanding of SDL  
and/or programming.  
Maybe you should solve this point instead of ignoring it and just switch  
to opengl.

I would suggest to reduce your current game code to a minimal game loop  
which still shows the worse scrolling and to post this demo code.  
It should be possible to write this code in say 20 to 50 lines of code  
(hopefully).

Or send it privately to me if you dont dare to post. But not just some code  
fragments: a minimal simple small running demo loop which shows the  
worse scrolling.

Thomas

---

<div class="post-metadata">

**Author:** ![David\_Olofson](https://discourse.libsdl.org/user_avatar/discourse.libsdl.org/david_olofson/32/115_2.png) [@David\_Olofson](https://discourse.libsdl.org/u/David_Olofson)\
**Post date:** [September 15, 2003, 5:53am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/9 "2003-09-15T05:53:01Z")

</div>

> IMHO its overkill to use OpenGL for a simple 2D game.

Probably - but then again, I considered purchasing a full version of  
“Raptor: Call of the shadows”, but never did, because there was no  
way I could get a decent frame rate on any hardware or OS it would  
run on. (It actually seems like the game has a logic frame rate limit  
somewhere around 20 fps or so.) The blurring or jerking that frame  
rates below ~60 Hz result in gives me a headache and makes it hard to  
see what’s going on.

I’m not sure what you mean by “simple”, but this applies to any game  
that scrolls a major area of the screen, unless it runs only in  
320x240 mode.

> As noted previously you would restrict your audience mainly  
> to people with hw-accelerated opengl-supported systems.

Or you could support both SDL 2D and OpenGL… glSDL is an easy way of  
doing that, while actually coding only for the SDL 2D API.

> And I dont think that this kind of people will play your 2D game  
> very long, because they maybe have lot of other real cool 3D games.

If they don’t, it’s because it’s a boring game. 3D doesn’t  
automatically make games better or more addictive.

> IMHO the audience for simple 2D games are for example children  
> (and their parents who have to buy the game…).

The vast majority of Kobo Deluxe players seem to be adults. 😉 And  
the game is probably way too hard for kids that are too young for 3D  
games…

Anyway, it’s a Free game, and I don’t know exactly how many active  
players there are, so I can’t really talk about an “audience” in the  
way you would about a commercial game.

> So to buy and play a simple game for their kids, they wuold have to  
> provide a hw-accel opengl system…  
> In my eyes an unnecessary additional restriction…

If s/w rendering is sufficient for most players, and h/w rendering is  
available for more demanding players (like myself), you get a  
_larger_ audience.

I think this is really worth considering for any game that does full  
screen scrolling in 640x480 or higher resolutions, since those  
usually never get close to full frame rate without h/w acceleration.

> Its possible to write a soft-scroller without opengl.

Sure, but it’s _not_ possible to get around the CPU\<-\>VRAM bandwidth  
limitations without using h/w acceleration.

That said…

> Maybe there  
> is something completely wrong in your main game loop or your  
> understanding of SDL and/or programming.  
> Maybe you should solve this point instead of ignoring it and just  
> switch to opengl.

…yes, that’s a good point. Forget abour arcade/console quality  
scrolling without OpenGL and sub-pixel accurate scrolling - but it  
should be possible to get playable frame rates with sane resolutions  
one any reasonably current hardware. Most players seem to be happy  
with anything better than 20-40 fps (depends on the game), so it’s  
definitely a good idea to try and support s/w rendering, if it’s  
realistic. (It may not be if you’re using tons of blending effects,  
transformations and stuff.)

[…]

//David Olofson - Programmer, Composer, Open Source Advocate

.- Audiality -----------------------------------------------.  
| Free/Open Source audio engine for games and multimedia. |  
| MIDI, modular synthesis, real time effects, scripting,… |  
`-----------------------------------\> [http://audiality.org](http://audiality.org) -’  
— [http://olofson.net](http://olofson.net) — [http://www.reologica.se](http://www.reologica.se) —On Monday 15 September 2003 13.59, Thomas Eder wrote:

---

<div class="post-metadata">

**Author:** ![Philip\_D.S\_Thoren](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/p/e47774/32.png) [@Philip\_D.S\_Thoren](https://discourse.libsdl.org/u/Philip_D.S_Thoren)\
**Post date:** [September 15, 2003, 2:25pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/10 "2003-09-15T14:25:01Z")

</div>

Is this game you’re writing using threads? Just curious

~ Phil Thoren

---

<div class="post-metadata">

**Author:** ![Michael\_Rickert](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/m/8491ac/32.png) [@Michael\_Rickert](https://discourse.libsdl.org/u/Michael_Rickert)\
**Post date:** [September 15, 2003, 4:59pm UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/11 "2003-09-15T16:59:01Z")

</div>

accidentally mailed myself instead of the list…  
ignore one line of indentation :)\> \> IMHO its overkill to use OpenGL for a simple 2D

> > game.
> 
> Agreed, however by the same logic it’s overkill to  
> use  
> a makefile or IDE for “Hello world”. That dosn’t  
> mean  
> you should try it anyways to learn, so you can  
> advance  
> to, say, an advance 2D game.
> 
> > As noted previously you would restrict your  
> > audience  
> > mainly  
> > to people with hw-accelerated opengl-supported  
> > systems.
> 
> to the original poster:  
> what _I_ would sugggest for _this particular_  
> problem  
> would be the workaround of two versions (either in  
> one  
> executable, selected at runtime, or two).
> 
> Version 1 would be what you have now… fixed at  
> 500x300, using sdl blits.
> 
> Version 2 would target those with more advanced  
> systems… with the higher resolution monitors,  
> which  
> are more likely to be supported by AGP cards which  
> can  
> handle such resolutions, or at the very least  
> supported by a processor of equal capacity.
> 
> Thus you provide an overkill _option_ for your  
> users.
> 
> > And I dont think that this kind of people will  
> > play  
> > your 2D game  
> > very long, because they maybe have lot of other  
> > real  
> > cool 3D games.
> 
> I’d play starcraft over 3d tic tac toe any day. The  
> point is the gameplay will dictate if players play  
> the  
> game, not if it’s 2d or 3d.
> 
> To the original poster:  
> If your game is indeed a “simple 2d game” I’d still  
> go  
> with my mentioned solution…it keeps your target  
> audience larger. However, IMHO learning to seperate  
> game from display is important…do so with your  
> next  
> game, so it can be run at 320x200 and 1600x1200 just  
> as well.
> 
> > IMHO the audience for simple 2D games are for  
> > example children  
> > (and their parents who have to buy the game…).
> 
> agreed if by simple you mean “very simple” or “most  
> simple”.
> 
> > So to buy and play a simple game for their kids,  
> > they wuold have to  
> > provide a hw-accel opengl system…  
> > In my eyes an unnecessary additional  
> > restriction…
> > 
> > Its possible to write a soft-scroller without  
> > opengl.
> 
> Indeed… he allready has a game, he’s asking about  
> fixing a problem with having hardcoded everything to  
> 500x300.
> 
> > Maybe there is something  
> > completely wrong in your main game loop or your  
> > understanding of SDL  
> > and/or programming.
> 
> He has learned… the thing he did wrong was to  
> hardcode the game to the display too much. It should  
> be able to handle multiple resolutions, and the game  
> mechanics itself should not depend on the screen at  
> all (hopefully they don’t!).
> 
> > Maybe you should solve this point instead of  
> > ignoring it and just switch  
> > to opengl.
> 
> Huh? I thought you were just arguing to keep his  
> code  
> in SDL?
> 
> > I would suggest to reduce your current game code  
> > to  
> > a minimal game loop  
> > which still shows the worse scrolling and to post  
> > this demo code.  
> > It should be possible to write this code in say 20  
> > to 50 lines of code  
> > (hopefully).
> 
> Ok now I’m confused… I thought the scrolling  
> problems were in another thread?
> 
> final words to the original poster:  
> If you have a simple 2d game that you want to allow  
> many people to be able to use, I’d go with my  
> allready  
> mentioned quick 'n dirty solution.
> 
> If you have an advanced 2d game etc etc, the best  
> thing would be to go ahead and rework your code so  
> it  
> isn’t resolution dependant… it’ll save you sanity  
> trying to maintain the game later.

* * *

Do you Yahoo!?  
Yahoo! SiteBuilder - Free, easy-to-use web site design software  
[http://sitebuilder.yahoo.com](http://sitebuilder.yahoo.com)

---

<div class="post-metadata">

**Author:** ![Henning](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/h/ecae2f/32.png) [@Henning](https://discourse.libsdl.org/u/Henning)\
**Post date:** [September 16, 2003, 1:19am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/12 "2003-09-16T01:19:01Z")

</div>

I think you’re mixing two posts together, I was not the one with the 500x300 display that needed a double pixel mode…?

> > with my mentioned solution…it keeps your target  
> > audience larger. However, IMHO learning to seperate  
> > game from display is important…do so with your

Yes, I have thought about that. I don’t really have a good sulution yet, but I will think about it. After all, I don’t see (right now) how a game will be the same in 640x480 and 1024x768 if it has a background image of 1280x800 that scrolls around.

> > If you have an advanced 2d game etc etc, the best  
> > thing would be to go ahead and rework your code so  
> > it  
> > isn’t resolution dependant… it’ll save you sanity  
> > trying to maintain the game later.

Seem like I have lots to learn. Not surprisingly.

Regards  
Henning

---

<div class="post-metadata">

**Author:** ![Henning](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/h/ecae2f/32.png) [@Henning](https://discourse.libsdl.org/u/Henning)\
**Post date:** [September 16, 2003, 2:47am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/13 "2003-09-16T02:47:01Z")

</div>

> I would suggest to reduce your current game code to a minimal game loop  
> which still shows the worse scrolling and to post this demo code.  
> It should be possible to write this code in say 20 to 50 lines of code  
> (hopefully).

Many thanks for your time then. Here it is, with what I thought was important to show my understanding (or lack thereof) of SDL.  
I have a 1024x768 image called “image.bmp” that I scroll around in circles, if you want to run it you just need to provide some other image for the prog.  
Everyone is welcome to comment, should they like of course.  
And no, so far I don’t use threads anywhere in the original code either.

Regards  
Henning

_CODE_

#include “SDL/SDL.h”  
SDL\_Surface \*screen;  
SDL\_Surface \*levelbg;  
SDL\_Surface \*levelbg\_bmp;

void updateScreen(int x, int y) {  
SDL\_Rect src;  
src.w=640;  
src.h=400;  
src.x=x;  
src.y=y;  
SDL\_BlitSurface(levelbg, &src, screen, NULL);  
SDL\_Flip(screen);  
}  
int main(int argc, char _argv[]) {  
SDL\_Event event;  
float x,y;  
x=y=0;  
SDL\_Init(SDL\_INIT\_VIDEO);  
atexit(SDL\_Quit);  
screen = SDL\_SetVideoMode(640,480,32,SDL\_FULLSCREEN|SDL\_HWSURFACE|SDL\_DOUBLEBUF);  
if (0 == screen-\>flags & SDL\_HWSURFACE)  
printf(“Can’t get hardware surface\n”);  
if (0 == screen-\>flags & SDL\_DOUBLEBUF)  
printf(“Can’t get doublebuf\n”);  
levelbg\_bmp = SDL\_LoadBMP(“image.bmp”);  
levelbg = SDL\_DisplayFormat(levelbg\_bmp);  
SDL\_SetColorKey(levelbg,  
SDL\_SRCCOLORKEY|SDL\_RLEACCEL,  
SDL\_MapRGB(levelbg-\>format,255,0,255));  
SDL\_FreeSurface(levelbg\_bmp);  
while(1) {  
SDL\_PollEvent(&event);  
if (event.key.keysym.sym == SDLK\_ESCAPE)  
break;  
updateScreen(300_cos(x+=0.004)+100,200\*sin(y+=0.004)+100);  
}  
return 0;  
}

---

<div class="post-metadata">

**Author:** ![steve\_houseman](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/s/839c29/32.png) [@steve\_houseman](https://discourse.libsdl.org/u/steve_houseman)\
**Post date:** [September 16, 2003, 3:44am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/14 "2003-09-16T03:44:01Z")

</div>

Hello Henning ,

well aside from the bad microsoft’s style of  
if( const == something )  
which I find irritating when reading ,

the precedence/binding of ‘==’ is higher than ‘&’ and so  
if (0 == screen-\>flags & SDL\_HWSURFACE)

is interpreted as

if( (0 == screen-\>flags ) & SDL\_HWSURFACE )

which is probably not what you wanted … me I bracket everything  
so I dont have to remember what the precedence is (bitten once too  
often 🙂

so writing it correctly …  
if( (screen-\>flags & SDL\_HWSURFACE) == 0 )

🙂

Cheers,

Steve Houseman–

currently : | for strace, an annotator see -  
@steve_houseman | [http://www.houseman.demon.co.uk/](http://www.houseman.demon.co.uk/)

---

<div class="post-metadata">

**Author:** ![Olof\_Bjarnason](https://discourse.libsdl.org/user_avatar/discourse.libsdl.org/olof_bjarnason/32/256_2.png) [@Olof\_Bjarnason](https://discourse.libsdl.org/u/Olof_Bjarnason)\
**Post date:** [September 16, 2003, 4:11am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/15 "2003-09-16T04:11:02Z")

</div>

One tip: add a line

SDL\_Delay(10);

… just after the updateScreen row. This will give your OS some “time  
to breathe” and might actually make your own program run smoother  
(since if you DON’T do this the OS will put your app to sleep as it  
see fits, and that might not be as you want it done, and might be  
the cause of non-smooth scrolling behaviour). Nowadays, we are  
trapped in a multitasking-environment and must adapt – sad but true.

/Olof

### Henning: “Re: [SDL] OpenGL or pure SDL gfx?” (2003-09-16 11:45)

#\> I would suggest to reduce your current game code to a minimal game loop  
#\> which still shows the worse scrolling and to post this demo code.  
#\> It should be possible to write this code in say 20 to 50 lines of code  
#\> (hopefully).#  
#Many thanks for your time then. Here it is, with what I thought was important to show my understanding (or lack thereof) of SDL.  
#I have a 1024x768 image called “image.bmp” that I scroll around in circles, if you want to run it you just need to provide some other image for the prog.  
#Everyone is welcome to comment, should they like of course.  
#And no, so far I don’t use threads anywhere in the original code either.

# 

#Regards  
#Henning

# 

# 

#_CODE_

# 

##include “SDL/SDL.h”  
#SDL\_Surface \*screen;  
#SDL\_Surface \*levelbg;  
#SDL\_Surface \*levelbg\_bmp;

# 

#void updateScreen(int x, int y) {

# SDL\_Rect src;

# src.w=640;

# src.h=400;

# src.x=x;

# src.y=y;

# SDL\_BlitSurface(levelbg, &src, screen, NULL);

# SDL\_Flip(screen);

#}  
#int main(int argc, char \*argv[]) {

# SDL\_Event event;

# float x,y;

# x=y=0;

# SDL\_Init(SDL\_INIT\_VIDEO);

# atexit(SDL\_Quit);

# screen = SDL\_SetVideoMode(640,480,32,SDL\_FULLSCREEN|SDL\_HWSURFACE|SDL\_DOUBLEBUF);

# if (0 == screen-\>flags & SDL\_HWSURFACE)

# printf(“Can’t get hardware surface\n”);

# if (0 == screen-\>flags & SDL\_DOUBLEBUF)

# printf(“Can’t get doublebuf\n”);

# levelbg\_bmp = SDL\_LoadBMP(“image.bmp”);

# levelbg = SDL\_DisplayFormat(levelbg\_bmp);

# SDL\_SetColorKey(levelbg,

# SDL\_SRCCOLORKEY|SDL\_RLEACCEL,

# SDL\_MapRGB(levelbg-\>format,255,0,255));

# SDL\_FreeSurface(levelbg\_bmp);

# while(1) {

# SDL\_PollEvent(&event);

# if (event.key.keysym.sym == SDLK\_ESCAPE)

# break;

# updateScreen(300_cos(x+=0.004)+100,200_sin(y+=0.004)+100);

# }

# return 0;

#}

# 

#\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_  
#SDL mailing list  
#SDL at [libsdl.org](http://libsdl.org)  
#[http://www.libsdl.org/mailman/listinfo/sdl](http://www.libsdl.org/mailman/listinfo/sdl)

#

---

<div class="post-metadata">

**Author:** ![David\_Olofson](https://discourse.libsdl.org/user_avatar/discourse.libsdl.org/david_olofson/32/115_2.png) [@David\_Olofson](https://discourse.libsdl.org/u/David_Olofson)\
**Post date:** [September 16, 2003, 5:02am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/16 "2003-09-16T05:02:01Z")

</div>

Right. CPU hogs can lose the CPU for extended periods of time (ie tens  
of ms) if any other process decides to do some work.

However, note that you should _not_ do this if you have drivers with  
proper (ie blocking rather than busy-waiting) retrace sync’ed  
pageflipping, because then it might cause unsmooth animation where  
you could have a steady full frame rate. It should probably be a user  
option…

//David Olofson - Programmer, Composer, Open Source Advocate

.- Audiality -----------------------------------------------.  
| Free/Open Source audio engine for games and multimedia. |  
| MIDI, modular synthesis, real time effects, scripting,… |  
`-----------------------------------\> [http://audiality.org](http://audiality.org) -’  
— [http://olofson.net](http://olofson.net) — [http://www.reologica.se](http://www.reologica.se) —On Tuesday 16 September 2003 13.10, Olof Bjarnason wrote:

> One tip: add a line
> 
> SDL\_Delay(10);
> 
> … just after the updateScreen row. This will give your OS some  
> “time to breathe” and might actually make your own program run  
> smoother (since if you DON’T do this the OS will put your app to  
> sleep as it see fits, and that might not be as you want it done,  
> and might be the cause of non-smooth scrolling behaviour).  
> Nowadays, we are trapped in a multitasking-environment and must  
> adapt – sad but true.

---

<div class="post-metadata">

**Author:** ![Milan\_Babuskov](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/m/f05b48/32.png) [@Milan\_Babuskov](https://discourse.libsdl.org/u/Milan_Babuskov)\
**Post date:** [September 16, 2003, 6:29am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/17 "2003-09-16T06:29:01Z")

</div>

David Olofson wrote:

> > IMHO the audience for simple 2D games are for example children  
> > (and their parents who have to buy the game…).
> 
> The vast majority of Kobo Deluxe players seem to be adults. 😉 And  
> the game is probably way too hard for kids that are too young for 3D  
> games…
> 
> Anyway, it’s a Free game, and I don’t know exactly how many active  
> players there are, so I can’t really talk about an “audience” in the  
> way you would about a commercial game.

Well, here’s one addict 😉 . I’m still struggling to get past that darn  
50th level…–  
Milan Babuskov  
[http://njam.sourceforge.net](http://njam.sourceforge.net)

---

<div class="post-metadata">

**Author:** ![David\_Olofson](https://discourse.libsdl.org/user_avatar/discourse.libsdl.org/david_olofson/32/115_2.png) [@David\_Olofson](https://discourse.libsdl.org/u/David_Olofson)\
**Post date:** [September 16, 2003, 7:16am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/18 "2003-09-16T07:16:01Z")

</div>

You might try being very defensive at first, getting rid of most of  
the blue bombs, before you start working on the base.

BTW, did you read the hints page? (Doesn’t mention level 50  
specifically, though.)

```
http://www.olofson.net/kobodl/hints.html

```

There are probably more hints that might be of use to people.  
Sugestions are welcome!

//David Olofson - Programmer, Composer, Open Source Advocate

.- Audiality -----------------------------------------------.  
| Free/Open Source audio engine for games and multimedia. |  
| MIDI, modular synthesis, real time effects, scripting,… |  
`-----------------------------------\> [http://audiality.org](http://audiality.org) -’  
— [http://olofson.net](http://olofson.net) — [http://www.reologica.se](http://www.reologica.se) —On Tuesday 16 September 2003 15.28, Milan Babuskov wrote:

> David Olofson wrote:
> 
> > > IMHO the audience for simple 2D games are for example children  
> > > (and their parents who have to buy the game…).
> > 
> > The vast majority of Kobo Deluxe players seem to be adults. 😉  
> > And the game is probably way too hard for kids that are too young  
> > for 3D games…
> > 
> > Anyway, it’s a Free game, and I don’t know exactly how many  
> > active players there are, so I can’t really talk about an  
> > “audience” in the way you would about a commercial game.
> 
> Well, here’s one addict 😉 . I’m still struggling to get past that  
> darn 50th level…

---

<div class="post-metadata">

**Author:** ![Milan\_Babuskov](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/m/f05b48/32.png) [@Milan\_Babuskov](https://discourse.libsdl.org/u/Milan_Babuskov)\
**Post date:** [September 16, 2003, 7:37am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/19 "2003-09-16T07:37:01Z")

</div>

David Olofson wrote:

> > Well, here’s one addict 😉 . I’m still struggling to get past that  
> > darn 50th level…
> 
> You might try being very defensive at first, getting rid of most of  
> the blue bombs, before you start working on the base.

I thought their supply is infinite, so I can get rid of them until the  
level is over ?!?!

> BTW, did you read the hints page? (Doesn’t mention level 50  
> specifically, though.)

Yes. That “diagonal” tip really helped.

> There are probably more hints that might be of use to people.  
> Sugestions are welcome!

Well, if I think of something really useful, I’ll let you know. ;)–  
Milan Babuskov  
[http://njam.sourceforge.net](http://njam.sourceforge.net)

---

<div class="post-metadata">

**Author:** ![Bob\_Pendleton](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/b/9de053/32.png) [@Bob\_Pendleton](https://discourse.libsdl.org/u/Bob_Pendleton)\
**Post date:** [September 16, 2003, 7:40am UTC](https://discourse.libsdl.org/t/opengl-or-pure-sdl-gfx/9341/20 "2003-09-16T07:40:01Z")

</div>

> > One tip: add a line
> > 
> > SDL\_Delay(10);
> > 
> > … just after the updateScreen row. This will give your OS some  
> > “time to breathe” and might actually make your own program run  
> > smoother (since if you DON’T do this the OS will put your app to  
> > sleep as it see fits, and that might not be as you want it done,  
> > and might be the cause of non-smooth scrolling behaviour).  
> > Nowadays, we are trapped in a multitasking-environment and must  
> > adapt – sad but true.
> 
> Right. CPU hogs can lose the CPU for extended periods of time (ie tens  
> of ms) if any other process decides to do some work.
> 
> However, note that you should _not_ do this if you have drivers with  
> proper (ie blocking rather than busy-waiting) retrace sync’ed  
> pageflipping, because then it might cause unsmooth animation where  
> you could have a steady full frame rate. It should probably be a user  
> option…

The problem is that you don’t know what the users drivers are doing and  
the user most likely does not know what they are doing either. Then  
there is the problem of drivers that synch by busy waiting so you don’t  
get any value out the synching anyway…

So, run a tiny test loop during initialization and use the delay() call  
if the frame rate is greater than 100 FPS or so. Not what you want to  
do, but the best you can do in an uncertain world.

```
	Bob PendletonOn Tue, 2003-09-16 at 07:01, David Olofson wrote:

```

> On Tuesday 16 September 2003 13.10, Olof Bjarnason wrote:

> //David Olofson - Programmer, Composer, Open Source Advocate
> 
> .- Audiality -----------------------------------------------.  
> | Free/Open Source audio engine for games and multimedia. |  
> | MIDI, modular synthesis, real time effects, scripting,… |  
> `-----------------------------------\> [http://audiality.org](http://audiality.org) -’  
> — [http://olofson.net](http://olofson.net) — [http://www.reologica.se](http://www.reologica.se) —
> 
> * * *
> 
> SDL mailing list  
> SDL at [libsdl.org](http://libsdl.org)  
> [http://www.libsdl.org/mailman/listinfo/sdl](http://www.libsdl.org/mailman/listinfo/sdl)  
> –  
> ±----------------------------------+

- Bob Pendleton: independent writer +
- and programmer. +
- email: Bob at [Pendleton.com](http://Pendleton.com) +
- web: [www.GameProgrammer.com](http://www.GameProgrammer.com) +  
±----------------------------------+

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