Lighting woes.

This is a discussion on Lighting woes. within the Game Programming forums, part of the General Programming Boards category; Every time I try and do something like this (lighting with shaders), it never quite works out the first time. ...

  1. #1
    The Right Honourable psychopath's Avatar
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    Lighting woes.

    Every time I try and do something like this (lighting with shaders), it never quite works out the first time.

    This is probably causes by some little thing I overlooked or haven't noticed yet, but I also never seem to figure anything out myself untill I've posted something about it here.

    Anyway, for some reason my lighting is messed up, even though these shaders worked on my old engine framework (causing me to think I screwed up my tangent space calculations like I usually do). The bump effect isn't there, and the lighting shows up in odd places (on other faces of the object, not facing the light).

    The shot below shows what i'm talking about. the light is between the two cubes, but it lights the corners of two of the other visible faces.

    My tangent/bitangent calculation:
    Code:
    void CObject::CalculateTB(){
    	float t1[2];
    	float t2[2];
    	float t3[2];
    	float tan[3];
    	float bitan[3];
    
    	for(int i=0; i<numMeshes; i++){
    		for(int j=0; j<mesh[i].numTriangles; j++){
    			int triangleIndex = mesh[i].triangleIndices[j];
    			const Triangle *triPtr = &triangle[triangleIndex];
    			int index[3];
    
    			index[0] = triPtr->vertexIndices[0];
    			index[1] = triPtr->vertexIndices[1];
    			index[2] = triPtr->vertexIndices[2];
    
    			t1[0] = triPtr->s[0];
    			t1[1] = triPtr->t[0];
    			t2[0] = triPtr->s[1];
    			t2[1] = triPtr->t[1];
    			t3[0] = triPtr->s[2];
    			t3[1] = triPtr->t[2];
    
    	
    			// -- TANGENT BASIS -- //
    			Vec3 V1, V2, V3;
    			V1 = V1.FromArray(vertex[index[0]].location);
    			V2 = V2.FromArray(vertex[index[1]].location);
    			V3 = V3.FromArray(vertex[index[2]].location);
    
    			Vec3 cp;
    			Vec3 e0(V2.x-V1.x, t2[0]-t1[0], t2[1]-t1[1]);
    			Vec3 e1(V3.x-V1.x, t3[0]-t1[0], t3[1]-t1[1]);
    
    			cp.Cross(e0, e1);
    			if(fabs(cp.x) > 0.000001f){
    				tan[0] = -cp.y/cp.x;
    				bitan[0] = -cp.z/cp.x;
    			}
    
    			e0.x = V2.y-V1.y;
    			e1.x = V3.y-V1.y;
    			cp.Cross(e0, e1);
    			if(fabs(cp.x) > 0.000001f){
    				tan[1] = -cp.y/cp.x;
    				bitan[1] = cp.z/cp.x;
    			}
    
    			e0.x = V2.z-V1.z;
    			e1.x = V3.z-V1.z;
    			cp.Cross(e0, e1);
    			if(fabs(cp.x) > 0.000001f){
    				tan[2] = -cp.y/cp.x;
    				bitan[2] = -cp.z/cp.x;
    			}
    			// -- TANGENT BASIS -- //
    
    			Vec3 tangent, bitangent;
    			tangent = tangent.FromArray(tan);
    			bitangent = bitangent.FromArray(bitan);
    			tangent.Normalize();
    			bitangent.Normalize();
    
    			for(int k=0; k<3; k++){
    				vertex[index[k]].tangent[0] = tangent.x;
    				vertex[index[k]].tangent[1] = tangent.y;
    				vertex[index[k]].tangent[2] = tangent.z;
    				vertex[index[k]].bitangent[0] = bitangent.x;
    				vertex[index[k]].bitangent[1] = bitangent.y;
    				vertex[index[k]].bitangent[2] = bitangent.z;
    			}
    		}
    	}
    }
    Is there something really obviously wrong with that code?

    Thanks.
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    Memorial University of Newfoundland
    Computer Science

    Mac and OpenGL evangelist.

  2. #2
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    I don't have time to look through the calculation at this moment, perhaps later. However, did you confirm that using just the diffuse component works without normal mapping?
    "...the results are undefined, and we all know what "undefined" means: it means it works during development, it works during testing, and it blows up in your most important customers' faces." --Scott Meyers

  3. #3
    The Right Honourable psychopath's Avatar
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    I hadn't confirmed it prior to posting, but I just checked then, and the version of the shader that doesn't use normal mapping works just fine. So the problem would have to be related to the normal mapping/tangent space stuff.
    Memorial University of Newfoundland
    Computer Science

    Mac and OpenGL evangelist.

  4. #4
    The Right Honourable psychopath's Avatar
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    I found one typo in this line:
    Code:
    bitan[1] = cp.z/cp.x;
    It should be -cp.z/cp.x. It didn't fix anything though.
    Last edited by psychopath; 08-19-2006 at 09:28 PM.
    Memorial University of Newfoundland
    Computer Science

    Mac and OpenGL evangelist.

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