void Lighting::gltMakeShadowMatrix(GLTVector3 vPoints[3], GLTVector4 vLightPos, GLTMatrix destMat)
{
GLTVector4 vPlaneEquation;
GLfloat dot;
gltGetPlaneEquation(vPoints[0], vPoints[1], vPoints[2], vPlaneEquation);
dot = vPlaneEquation[0]*vLightPos[0] +
vPlaneEquation[1]*vLightPos[1] +
vPlaneEquation[2]*vLightPos[2] +
vPlaneEquation[3]*vLightPos[3];
destMat[0] = dot - vLightPos[0] * vPlaneEquation[0];
destMat[4] = 0.0f - vLightPos[0] * vPlaneEquation[1];
destMat[8] = 0.0f - vLightPos[0] * vPlaneEquation[2];
destMat[12] = 0.0f - vLightPos[0] * vPlaneEquation[3];
destMat[1] = 0.0f - vLightPos[1] * vPlaneEquation[0];
destMat[5] = dot - vLightPos[1] * vPlaneEquation[1];
destMat[9] = 0.0f - vLightPos[1] * vPlaneEquation[2];
destMat[13] = 0.0f - vLightPos[1] * vPlaneEquation[3];
destMat[2] = 0.0f - vLightPos[2] * vPlaneEquation[0];
destMat[6] = 0.0f - vLightPos[2] * vPlaneEquation[1];
destMat[10] = dot - vLightPos[2] * vPlaneEquation[2];
destMat[14] = 0.0f - vLightPos[2] * vPlaneEquation[3];
destMat[3] = 0.0f - vLightPos[3] * vPlaneEquation[0];
destMat[7] = 0.0f - vLightPos[3] * vPlaneEquation[1];
destMat[11] = 0.0f - vLightPos[3] * vPlaneEquation[2];
destMat[15] = dot - vLightPos[3] * vPlaneEquation[3];
}
// Creates a shadow projection matrix out of the plane equation
// coefficients and the position of the light. The return value is stored
// in destMat
void gltMakeShadowMatrix(GLTVector3 vPoints[3], GLTVector4 vLightPos, GLTMatrix destMat)
{
GLTVector4 vPlaneEquation;
GLfloat dot;
gltGetPlaneEquation(vPoints[0], vPoints[1], vPoints[2], vPlaneEquation);
// Dot product of plane and light position
dot = vPlaneEquation[0]*vLightPos[0] +
vPlaneEquation[1]*vLightPos[1] +
vPlaneEquation[2]*vLightPos[2] +
vPlaneEquation[3]*vLightPos[3];
// Now do the projection
// First column
destMat[0] = dot - vLightPos[0] * vPlaneEquation[0];
destMat[4] = 0.0f - vLightPos[0] * vPlaneEquation[1];
destMat[8] = 0.0f - vLightPos[0] * vPlaneEquation[2];
destMat[12] = 0.0f - vLightPos[0] * vPlaneEquation[3];
// Second column
destMat[1] = 0.0f - vLightPos[1] * vPlaneEquation[0];
destMat[5] = dot - vLightPos[1] * vPlaneEquation[1];
destMat[9] = 0.0f - vLightPos[1] * vPlaneEquation[2];
destMat[13] = 0.0f - vLightPos[1] * vPlaneEquation[3];
// Third Column
destMat[2] = 0.0f - vLightPos[2] * vPlaneEquation[0];
destMat[6] = 0.0f - vLightPos[2] * vPlaneEquation[1];
destMat[10] = dot - vLightPos[2] * vPlaneEquation[2];
destMat[14] = 0.0f - vLightPos[2] * vPlaneEquation[3];
// Fourth Column
destMat[3] = 0.0f - vLightPos[3] * vPlaneEquation[0];
destMat[7] = 0.0f - vLightPos[3] * vPlaneEquation[1];
destMat[11] = 0.0f - vLightPos[3] * vPlaneEquation[2];
destMat[15] = dot - vLightPos[3] * vPlaneEquation[3];
}