Clipping question

SDL Development
#1

SDL automatically clips blits to the screen surface.

Does this make checking in your own code whether or not a given sprite is
on the screen pointless and inefficient?

If you have 500 sprites, and only a small proportion of them are likely
to be on the screen, should you just blit all 500 of them in any case and
let SDL_BlitSurface sort it out?

Thanks,

James
#2

SDL automatically clips blits to the screen surface.

Does this make checking in your own code whether or not a given sprite is
on the screen pointless and inefficient?

If you have 500 sprites, and only a small proportion of them are likely
to be on the screen, should you just blit all 500 of them in any case and
let SDL_BlitSurface sort it out?

If you can efficiently tell whether or not the sprite is on-screen, maybe
with a bit-flag, then you should do it. Otherwise, you can let SDL sort
it out, but passing lots of empty rectangles to SDL_UpdateRects() isn’t
a great idea for performance. :slight_smile:

See ya,
-Sam Lantinga, Software Engineer, Blizzard Entertainment

#3

SDL automatically clips blits to the screen surface.

Does this make checking in your own code whether or not a given sprite is
on the screen pointless and inefficient?

If you have 500 sprites, and only a small proportion of them are likely
to be on the screen, should you just blit all 500 of them in any case and
let SDL_BlitSurface sort it out?

If you can efficiently tell whether or not the sprite is on-screen, maybe
with a bit-flag, then you should do it. Otherwise, you can let SDL sort
it out, but passing lots of empty rectangles to SDL_UpdateRects() isn’t
a great idea for performance. :slight_smile:

Thanks…

JamesOn Mon, 09 Feb 2004 04:38:48 -0800, Sam Lantinga wrote:
#4

Hi, I’m new in this list.
I’m trying to make a SDL_Surface semi-transparent over a openGL scene.
There is any tutorial about how to do this ?
Thank, Marce.
Saludos, Marce.
http://personales.ciudad.com.ar/MarcelaNoemiNievas--------
E-mail y acceso a Internet UltraVeloz totalmente GRATIS en Buenos Aires,
Rosario, Cordoba, Mendoza, La Plata y Pilar
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#5

You can just apply alpha blending to your quad that has the surface textured
to it, if you’re working at a whole surface level.
Doesn’t need to be a property of the image at all.> ----- Original Message -----

From: nievas_marcela@argentina.com (Marce)
To:
Sent: Wednesday, February 11, 2004 12:38 AM
Subject: [SDL] Transaprency over OpenGL

Hi, I’m new in this list.
I’m trying to make a SDL_Surface semi-transparent over a openGL scene.
There is any tutorial about how to do this ?
Thank, Marce.
Saludos, Marce.
http://personales.ciudad.com.ar/MarcelaNoemiNievas

E-mail y acceso a Internet UltraVeloz totalmente GRATIS en Buenos Aires,
Rosario, Cordoba, Mendoza, La Plata y Pilar
http://www.Argentina.com
Nro. de acceso 5078-5000 Usuario: Argentina Password: Argentina

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