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env mapping

Started by taybrin Dec 2, 2001 at 4:27 PM 1 reply 600+ views

Original Post

Dec 2, 2001 at 4:27 PM

Hey everyone, I have a routine to draw a cylinder and I have environment mapping turned on by the following:bool emap = true;

  	
if(emap) {
    glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
		glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
	glEnable(GL_TEXTURE_GEN_S);
	glEnable(GL_TEXTURE_GEN_T);
              }
	}

The very ends of my cylinder are drawn with trianges. Each triagnle starts at (0,0,0) or (height, 0, 0) depending on which end cap i am drawing. When I do regular texturing everything works fine, but when i do environment map texturing, as above, one triangle of the capped ends will show some random portion of the environment mapped image. I am drawing all of my triangles in the correct order and this is really frustrating me . . .does anyone have any ideas. If clarification is needed please feel free to ask. Matt

Dodger

Dec 3, 2001 at 11:13 AM

Make sure the normals of all vertices are correct. Sphere mapping computes a reflection vector in eyespace from the view vector and the vertices'' normals - sounds to me like one of your normals may be messed up.

taybrin

Author

taybrin

Dec 4, 2001 at 2:26 PM

Funny thing is, the normal for the bottom of a cylinder (-1.0, 0.0, 0.0) assuming that the cylinder lies on the x-axis. So in my primitive drawing routine I only have one call to glNormal and it happens before I draw any triangles for the base of the cylinder.

What is even funnier is that on Windows everything runs fine, but on Mesa (OGL for Solaris I think) . . . I get the weird chipping effects.

Oh well, any feedback would be great

Matt

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