GL_COLOR_MATERIAL problems

OpenGL OpenGL: Basic Coding
1

I’m trying to render a lightened scene with textured and colored polygons. Rendering textured polygons works well, but colored polygons are all white. So I tryed to use GL_COLOR_MATERIAL to render my colored polygons. My render loop is like that:

{
glEnable(GL_TEXTURE_2D);
glDisable(GL_COLOR_MATERIAL);
DrawTexturedObjects();

glDisable(GL_TEXTURE_2D);
glEnable(GL_COLOR_MATERIAL);
DrawColoredObjects();
}

The problem is, glDisable(GL_COLOR_MATERIAL) doesn’t work! The first frame is rendered correctly, but once GL_COLOR_MATERIAL has been enabled, I can’t disable it, so the next frames are incorrect (textured objects are no longer lit because GL_COLOR_MATERIAL is enabled).

2

Hi !

If you try to use glColor to change the color of a polygon that will not work unless you disable lighting first (glDiable( GL_LIGHTING))

Could that be the reason for the white polygons.

glDisable( GL_COLOR_MATERIAL) only disables the tracking, the last used glColor will still be active for the last changed material, so you would need to reset this with a last glColor before disable GL_COLOR_MATERIAL, or better reset the material before you start rendering.

Mikael

3

Thanks fot answering.

I use GL_COLOR_MATERIAL so my colored polygons are not white. The problem is that GL_COLOR_MATERIAL cancel the light effect on my textured polygons(probably because I didn’t set any material property on those). Ans disabling GL_COLOR_MATERIAL doesn’t change anything.

As for reseting the color to white, it makes my textured polygons have the right colors, but I still have no lighting on them.

Hope you understanf what I mean. Maybe I should just use material for everything, but then it would be slower I think.

4

Well I just solved my problem, which was an ambient light acting strangely. :slight_smile:

5

I’m having the same problem with lighting on a textured polygon. I’ve created a texture map and have generated colors according to a contour color scheme I want. I’ve set up the texture, material and lighting properties then display it like this:

//needed here for blended shading model at each redraw
	glShadeModel(GL_SMOOTH);
	
	if(texture){
		//uses predefined texture from setParams()
		glBindTexture(GL_TEXTURE_2D, textures[1]);
		//turns on texturing
		glEnable(GL_TEXTURE_2D);
	}
	
	glEnable(GL_COLOR_MATERIAL);

	//select the current color according to color scheme
	if (colorScheme == DARK) glColor3f(0.25f,0.25f,0.25f);
	if (colorScheme == LIGHT) glColor3f(0.8f,0.8f,0.8f);
	if (colorScheme == MIDDLE) glColor3f(0.4f,0.4f,0.4f);

	//draw "terrain" object then put texture on it
	start = FSIZE/8;
	end   = FSIZE*7/8;
	cent  = float(FSIZE)/2.0f;

	glPushMatrix();	
	glTranslatef(-cent,-cent,-10.5);
	
	for(i=start;i<end;++i){
		glBegin(GL_QUAD_STRIP);
		for(j=start;j<end;++j){
			//set the normals for the surface rendered
			glNormal3f(normsX[i][j],normsY[i][j],normsZ[i][j]);
			//sets the current texture coordinates
			glTexCoord2f(field[i][j]*b + a, field[i][j]*b + a);
			//vertex to be rendered
			glVertex3f(float(i),float(j),field[i][j]);
			//repeat
			glNormal3f(normsX[i+1][j],normsY[i+1][j],normsZ[i+1][j]);
			glTexCoord2f(field[i+1][j]*b + a, field[i+1][j]*b + a);
			glVertex3f(float(i+1),float(j),field[i+1][j]);
		}
		glEnd();
	}

	glDisable(GL_TEXTURE_2D);

This all works fine! My problem is that when I try to change the RGB values for the texture so the glColor3f that I use can be

glColor3f(1.0f,1.0f,1.0f);

I loose the specular highlighting. Can you, or anyone explain why? And how can I get the highlighting back if I want to keep the glColor3f values all 1.0?
-I assumed that the glColor values would just be a percentage of the texture color values, which would mean there should be a way for me to set the numbers up so I wouldn’t have to give a specific percentage value when calling glColor3f
THANKS :smiley: