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OpenGL inverse projection matrix
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/* | |
Based off http://bookofhook.com/mousepick.pdf | |
OpenGL matrix order | |
m0 m4 m8 m12 | |
m1 m5 m9 m13 | |
m2 m6 m10 m14 | |
m3 m7 m11 m15 | |
Projection matrix | |
a 0 0 0 | |
0 b 0 0 | |
0 0 c d | |
0 0 e 0 | |
Inverse projection | |
1/a, 0, 0, 0, | |
0, 1/b, 0, 0, | |
0, 0, 0, 1/e, | |
0, 0, 1/d, -c/(d*e) | |
*/ | |
double op[16]; // original projection matrix | |
glGetDoublev(GL_PROJECTION_MATRIX, op); | |
double a = op[0]; | |
double b = op[5]; | |
double c = op[10]; | |
double d = op[14]; | |
double e = op[11]; | |
double inverseProject[16] = { 0.0 }; | |
inverseProject[0] = 1.0 / a; | |
inverseProject[5] = 1.0 / b; | |
inverseProject[11] = 1.0 / d; | |
inverseProject[14] = 1.0 / e; | |
inverseProject[15] = -c / (d * e); | |
//glLoadMatrixd(inverseProject); |
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