Opengl textures?

SDL Development
1

Hi

how to create textures for Opengl with help of SDL?
the following code work not
but the odd thing is if I replace the glTexImage2D with gluBuild2DMipmaps
it works, but tehn only the last loaded texture is on everything, it’s always
bound even if gl_BindTexture is not called!

Please help me!

gload_texture(&texture[0], “texture.tga”);

void gload_texture(GLuint *texture, const char filename)
{
string ext = strrchr(filename, ‘.’);
SDL_Surface image=IMG_Load(filename);

if(!image)
{
	cout<<"failed to load texture \""<<filename<<endl;
	return;
}

int width=image->w;
	int height=image->h;
	unsigned char *data=(unsigned char *)(image->pixels);
	int BytesPerPixel=(image->format->BytesPerPixel);

for(int i=0; i<(height/2); ++i)
for(int j=0; j<width*BytesPerPixel; j+=BytesPerPixel)
for(int k=0; k<BytesPerPixel; ++k)
swap(data[(i*width*BytesPerPixel)+j+k], data[((height-i-1)*width*BytesPerPixel)+j+k]);


glGenTextures(1, texture);
glBindTexture(GL_TEXTURE_2D, *texture);

if(ext==".tga" || ext==".png" || ext==".xfc" || ext==".tif")
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image->w, image->h, 0,	GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);
else
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image->w, image->h, 0, GL_RGB, GL_UNSIGNED_BYTE, image->pixels);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

	SDL_FreeSurface(image);

}

btw, how to test if an image has alpha?

Thank in advance–
funthing

2

Hi

how to create textures for Opengl with help of SDL?
the following code work not
but the odd thing is if I replace the glTexImage2D with gluBuild2DMipmaps
it works, but tehn only the last loaded texture is on everything, it’s always
bound even if gl_BindTexture is not called!

Please help me!

Of course it shouldn’t work. In glTexImage2D you can’t give width and
height which is not 2^n (or +1 if using borders) Read OpenGL tutorials or
redbook.
How to determine if surface have alfa channel? I am checking
SDL_Surface->format->Amask (maybe it is wrong but it is functional for me
purposes)
KrataOn Sat, 6 Jul 2002, Matthias wrote:

gload_texture(&texture[0], “texture.tga”);

void gload_texture(GLuint *texture, const char filename)
{
string ext = strrchr(filename, ‘.’);
SDL_Surface image=IMG_Load(filename);

if(!image)
{
cout<<“failed to load texture "”<<filename<<endl;
return;
}

int width=image->w;
int height=image->h;
unsigned char *data=(unsigned char *)(image->pixels);
int BytesPerPixel=(image->format->BytesPerPixel);

for(int i=0; i<(height/2); ++i)
for(int j=0; j<widthBytesPerPixel; j+=BytesPerPixel)
for(int k=0; k<BytesPerPixel; ++k)
swap(data[(iwidth*BytesPerPixel)+j+k], data[((height-i-1)widthBytesPerPixel)+j+k]);

glGenTextures(1, texture);
glBindTexture(GL_TEXTURE_2D, *texture);

if(ext==“.tga” || ext==“.png” || ext==“.xfc” || ext==“.tif”)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image->w, image->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);
else
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image->w, image->h, 0, GL_RGB, GL_UNSIGNED_BYTE, image->pixels);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

	SDL_FreeSurface(image);

}

btw, how to test if an image has alpha?

Thank in advance

funthing

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

3

Hi folks!

SDL works great, but I want’t know if the following thing is justified?
SDL_GL_SwapBuffers pulls down the framerate on a remarkable hunk!

idle (only fps_counter): ~ 34 000 FPS (I know here we don’t any fps, but loop per second)

  • SDL_GL_SwapBuffers(): ~ 1 700 FPS

I this right?

if not here are some specs:

screen = SDL_SetVideoMode(1024, 768, 32, SDL_OPENGL|SDL_RESIZABLE );
Linux, NVIDIA_glx, 1.4 GHZ, GF4Ti

Are there any options to add like SDL_SetVideoMode(x,x,x,…?);
or SDL_GL_SetAttribute(…?);

thx, in advance!–
funthing

4

When in a window, GL_SwapBuffers usually has to do actual blits, which
takes some time. Try it in fullscreen, with vsync disabled. (I don’t
think SDL gives any way to set vsync, though, and I don’t know how to
set it with glx.)On Sun, Dec 08, 2002 at 09:11:36PM +0100, Matthias wrote:

SDL works great, but I want’t know if the following thing is justified?
SDL_GL_SwapBuffers pulls down the framerate on a remarkable hunk!

idle (only fps_counter): ~ 34 000 FPS (I know here we don’t any fps, but loop per second)

  • SDL_GL_SwapBuffers(): ~ 1 700 FPS

I this right?

if not here are some specs:

screen = SDL_SetVideoMode(1024, 768, 32, SDL_OPENGL|SDL_RESIZABLE );
Linux, NVIDIA_glx, 1.4 GHZ, GF4Ti

Are there any options to add like SDL_SetVideoMode(x,x,x,…?);
or SDL_GL_SetAttribute(…?);

–
Glenn Maynard