problem of opengl extention

OpenGL OpenGL: Advanced Coding
1

I use
glActiveTextureARB
glMultiTexCoord2fARB
to do multi_texturing.

It is working. But after I use this, the drawing code after this seems can not bind textures any more.

Is it the bug of opengl extention?
Or I need to do something after things done?

the following is my code:

//initializing multi texturing
g_misc.glActiveTextureARB		= (PFNGLACTIVETEXTUREARBPROC)		wglGetProcAddress("glActiveTextureARB");
g_misc.glMultiTexCoord2fARB	= (PFNGLMULTITEXCOORD2FARBPROC)		wglGetProcAddress("glMultiTexCoord2fARB");

if(!g_misc.glActiveTextureARB | | !g_misc.glMultiTexCoord2fARB)
{
	g_able_multi_texturing=0;
	g_out.Insert("This version of OpenGL does not support multitexturing!

");
}
else
g_able_multi_texturing=1;

g_misc.cloud_texture_index = 
	CMy_misc_func::load_general_texture("fog.bmp");

	g_misc.glActiveTextureARB(GL_TEXTURE0_ARB);
	glBindTexture(GL_TEXTURE_2D,  g_tex_general[g_play_ground_box_texture[BOX_RIGHT]].ID);
	g_misc.glActiveTextureARB(GL_TEXTURE1_ARB);
	glBindTexture(GL_TEXTURE_2D,  g_tex_general[g_misc.cloud_texture_index].ID);

	glBegin(GL_QUADS);		
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0f, 0.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0f - wrap, 0.0f);
	glVertex3f(x + width, y,			z);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0f, 0.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0f - wrap, 0.0f);
	glVertex3f(x + width, y,			z + depth);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0f, 1.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0f - wrap, 1.0f);
	glVertex3f(x + width, y + height,	z + depth); 
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0f, 1.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0f - wrap, 1.0f);
	glVertex3f(x + width, y + height,	z);
	glEnd();
2

When your finished drawing you should disable your textures like this:
glActiveTextureARB( GL_TEXTURE0_ARB );
glDisable( GL_TEXTURE_2D );
glActiveTextureARB( GL_TEXTURE1_ARB );
glDisable( GL_TEXTURE_2D );

Now if you are not using GL_TEXTURE_2D for one or more of the texture units then replace GL_TEXTURE_2D in the disable func with what ever your using. So if for example your using a cube map in texture unit 1 you should do this:

glActiveTextureARB( GL_TEXTURE1_ARB );
glDisable( GL_TEXTURE_CUBE_MAP_ARB );

-SirKnight

3

Hi, thanks for the reply.
But seems not work. I do not use any features other than GL_TEXTURE_2D. There is anything else I should take care of?
Thank in advance.

the code again:
g_misc.glActiveTextureARB(GL_TEXTURE0_ARB);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, g_tex_general[g_play_ground_box_texture[BOX_RIGHT]].ID);
g_misc.glActiveTextureARB(GL_TEXTURE1_ARB);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, g_tex_general[g_misc.cloud_texture_index].ID);

	glBegin(GL_QUADS);		
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0f, 0.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0f - wrap, 0.0f);
	glVertex3f(x + width, y,			z);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0f, 0.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0f - wrap, 0.0f);
	glVertex3f(x + width, y,			z + depth);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0f, 1.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0f - wrap, 1.0f);
	glVertex3f(x + width, y + height,	z + depth); 
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0f, 1.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0f - wrap, 1.0f);
	glVertex3f(x + width, y + height,	z);
	glEnd();
	
	g_misc.glActiveTextureARB(GL_TEXTURE0_ARB);
	glDisable(GL_TEXTURE_2D);
	g_misc.glActiveTextureARB(GL_TEXTURE1_ARB);
	glDisable(GL_TEXTURE_2D);

	//glDisable(GL_TEXTURE_2D);
4

I prefer activating textures starting with the biggest one and ending with GL_TEXTURE0_ARB. The same for disabling: Start with biggest active texture stage so that at the end you disable GL_TEXTURE0_ARB. Now you know that you always are in stage 0. In your code just exchange the order of GL_TEXTURE0_ARB and GL_TEXTURE1_ARB calls and when drawing another textured object don’t forget enabling texturing again.

kon

5

thank a lot, it is working.
I did not change anything other than the ordering and I works fine. I think it is a bug in openGL extension.

The code again and thanks again:

	static float wrap = 0;
	wrap += 0.0015f;

	g_misc.glActiveTextureARB(GL_TEXTURE1_ARB);
	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D,  g_tex_general[g_misc.cloud_texture_index].ID);
	g_misc.glActiveTextureARB(GL_TEXTURE0_ARB);
	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D,  g_tex_general[g_play_ground_box_texture[BOX_RIGHT]].ID);

	glBegin(GL_QUADS);		
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0f, 0.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0f - wrap, 0.0f);
	glVertex3f(x + width, y,			z);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0f, 0.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0f - wrap, 0.0f);
	glVertex3f(x + width, y,			z + depth);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0f, 1.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0f - wrap, 1.0f);
	glVertex3f(x + width, y + height,	z + depth); 
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0f, 1.0f);
	g_misc.glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0f - wrap, 1.0f);
	glVertex3f(x + width, y + height,	z);
	glEnd();
	
	g_misc.glActiveTextureARB(GL_TEXTURE1_ARB);
	glDisable(GL_TEXTURE_2D);
	g_misc.glActiveTextureARB(GL_TEXTURE0_ARB);
	glDisable(GL_TEXTURE_2D);
6

It’s not a bug, it seems you were previously leaving your active texture unit to be unit 1, when you assumed it would be unit 0.

Nutty

7

emmmmm, thx!
I think you are right.