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copied!<p>Okay, okay that was still a bit buggy. Here is what is MOSTLY working now:</p> <pre><code>-(void)view2WorldPoint:(CGPoint)point :(GLfloat*)worldPoint { float clickX = point.x; float clickY = point.y; float clickZ = -near; //viewport -> normalized device coord -> clip GLint viewport[4]; glGetIntegerv(GL_VIEWPORT, viewport); GLfloat n[] = { (clickX - (float)viewport[0]) / (float)viewport[2] * 2.0 - 1.0, -((clickY - (float)viewport[1]) / (float)viewport[3] * 2.0 - 1.0), 2.0 * clickZ - 1.0, 1.0 }; GLfloat MP[16], MPInv[16]; MatMatMultiply(MP, projMat, modelMat); GenerateInverseMatrix4f(MPInv, MP); // replace this one with the whole 1/p thang? GLfloat w[] = { (MPInv[0] * n[0]) + (MPInv[4] * n[1]) + (MPInv[8] * n[2]) + (MPInv[12] * n[3]), (MPInv[1] * n[0]) + (MPInv[5] * n[1]) + (MPInv[9] * n[2]) + (MPInv[13] * n[3]), (MPInv[2] * n[0]) + (MPInv[6] * n[1]) + (MPInv[10] * n[2]) + (MPInv[14] * n[3]), (MPInv[3] * n[0]) + (MPInv[7] * n[1]) + (MPInv[11] * n[2]) + (MPInv[15] * n[3]) }; worldPoint[0] = w[0] / w[3]; worldPoint[1] = w[1] / w[3]; worldPoint[2] = w[2] / w[3]; } float Determinant4f(const float m[16]) { return m[12]*m[9]*m[6]*m[3]- m[8]*m[13]*m[6]*m[3]- m[12]*m[5]*m[10]*m[3]+ m[4]*m[13]*m[10]*m[3]+ m[8]*m[5]*m[14]*m[3]- m[4]*m[9]*m[14]*m[3]- m[12]*m[9]*m[2]*m[7]+ m[8]*m[13]*m[2]*m[7]+ m[12]*m[1]*m[10]*m[7]- m[0]*m[13]*m[10]*m[7]- m[8]*m[1]*m[14]*m[7]+ m[0]*m[9]*m[14]*m[7]+ m[12]*m[5]*m[2]*m[11]- m[4]*m[13]*m[2]*m[11]- m[12]*m[1]*m[6]*m[11]+ m[0]*m[13]*m[6]*m[11]+ m[4]*m[1]*m[14]*m[11]- m[0]*m[5]*m[14]*m[11]- m[8]*m[5]*m[2]*m[15]+ m[4]*m[9]*m[2]*m[15]+ m[8]*m[1]*m[6]*m[15]- m[0]*m[9]*m[6]*m[15]- m[4]*m[1]*m[10]*m[15]+ m[0]*m[5]*m[10]*m[15]; } BOOL GenerateInverseMatrix4f(float i[16], const float m[16]) { float x=Determinant4f(m); if (x==0) return FALSE; i[0]= (-m[13]*m[10]*m[7] +m[9]*m[14]*m[7] +m[13]*m[6]*m[11] -m[5]*m[14]*m[11] -m[9]*m[6]*m[15] +m[5]*m[10]*m[15])/x; i[4]= ( m[12]*m[10]*m[7] -m[8]*m[14]*m[7] -m[12]*m[6]*m[11] +m[4]*m[14]*m[11] +m[8]*m[6]*m[15] -m[4]*m[10]*m[15])/x; i[8]= (-m[12]*m[9]* m[7] +m[8]*m[13]*m[7] +m[12]*m[5]*m[11] -m[4]*m[13]*m[11] -m[8]*m[5]*m[15] +m[4]*m[9]* m[15])/x; i[12]=( m[12]*m[9]* m[6] -m[8]*m[13]*m[6] -m[12]*m[5]*m[10] +m[4]*m[13]*m[10] +m[8]*m[5]*m[14] -m[4]*m[9]* m[14])/x; i[1]= ( m[13]*m[10]*m[3] -m[9]*m[14]*m[3] -m[13]*m[2]*m[11] +m[1]*m[14]*m[11] +m[9]*m[2]*m[15] -m[1]*m[10]*m[15])/x; i[5]= (-m[12]*m[10]*m[3] +m[8]*m[14]*m[3] +m[12]*m[2]*m[11] -m[0]*m[14]*m[11] -m[8]*m[2]*m[15] +m[0]*m[10]*m[15])/x; i[9]= ( m[12]*m[9]* m[3] -m[8]*m[13]*m[3] -m[12]*m[1]*m[11] +m[0]*m[13]*m[11] +m[8]*m[1]*m[15] -m[0]*m[9]* m[15])/x; i[13]=(-m[12]*m[9]* m[2] +m[8]*m[13]*m[2] +m[12]*m[1]*m[10] -m[0]*m[13]*m[10] -m[8]*m[1]*m[14] +m[0]*m[9]* m[14])/x; i[2]= (-m[13]*m[6]* m[3] +m[5]*m[14]*m[3] +m[13]*m[2]*m[7] -m[1]*m[14]*m[7] -m[5]*m[2]*m[15] +m[1]*m[6]* m[15])/x; i[6]= ( m[12]*m[6]* m[3] -m[4]*m[14]*m[3] -m[12]*m[2]*m[7] +m[0]*m[14]*m[7] +m[4]*m[2]*m[15] -m[0]*m[6]* m[15])/x; i[10]=(-m[12]*m[5]* m[3] +m[4]*m[13]*m[3] +m[12]*m[1]*m[7] -m[0]*m[13]*m[7] -m[4]*m[1]*m[15] +m[0]*m[5]* m[15])/x; i[14]=( m[12]*m[5]* m[2] -m[4]*m[13]*m[2] -m[12]*m[1]*m[6] +m[0]*m[13]*m[6] +m[4]*m[1]*m[14] -m[0]*m[5]* m[14])/x; i[3]= ( m[9]* m[6]* m[3] -m[5]*m[10]*m[3] -m[9]* m[2]*m[7] +m[1]*m[10]*m[7] +m[5]*m[2]*m[11] -m[1]*m[6]* m[11])/x; i[7]= (-m[8]* m[6]* m[3] +m[4]*m[10]*m[3] +m[8]* m[2]*m[7] -m[0]*m[10]*m[7] -m[4]*m[2]*m[11] +m[0]*m[6]* m[11])/x; i[11]=( m[8]* m[5]* m[3] -m[4]*m[9]* m[3] -m[8]* m[1]*m[7] +m[0]*m[9]* m[7] +m[4]*m[1]*m[11] -m[0]*m[5]* m[11])/x; i[15]=(-m[8]* m[5]* m[2] +m[4]*m[9]* m[2] +m[8]* m[1]*m[6] -m[0]*m[9]* m[6] -m[4]*m[1]*m[10] +m[0]*m[5]* m[10])/x; return TRUE; } void MatMatMultiply(GLfloat *result, GLfloat *matrix1, GLfloat *matrix2) { result[0]=matrix1[0]*matrix2[0]+ matrix1[4]*matrix2[1]+ matrix1[8]*matrix2[2]+ matrix1[12]*matrix2[3]; result[4]=matrix1[0]*matrix2[4]+ matrix1[4]*matrix2[5]+ matrix1[8]*matrix2[6]+ matrix1[12]*matrix2[7]; result[8]=matrix1[0]*matrix2[8]+ matrix1[4]*matrix2[9]+ matrix1[8]*matrix2[10]+ matrix1[12]*matrix2[11]; result[12]=matrix1[0]*matrix2[12]+ matrix1[4]*matrix2[13]+ matrix1[8]*matrix2[14]+ matrix1[12]*matrix2[15]; result[1]=matrix1[1]*matrix2[0]+ matrix1[5]*matrix2[1]+ matrix1[9]*matrix2[2]+ matrix1[13]*matrix2[3]; result[5]=matrix1[1]*matrix2[4]+ matrix1[5]*matrix2[5]+ matrix1[9]*matrix2[6]+ matrix1[13]*matrix2[7]; result[9]=matrix1[1]*matrix2[8]+ matrix1[5]*matrix2[9]+ matrix1[9]*matrix2[10]+ matrix1[13]*matrix2[11]; result[13]=matrix1[1]*matrix2[12]+ matrix1[5]*matrix2[13]+ matrix1[9]*matrix2[14]+ matrix1[13]*matrix2[15]; result[2]=matrix1[2]*matrix2[0]+ matrix1[6]*matrix2[1]+ matrix1[10]*matrix2[2]+ matrix1[14]*matrix2[3]; result[6]=matrix1[2]*matrix2[4]+ matrix1[6]*matrix2[5]+ matrix1[10]*matrix2[6]+ matrix1[14]*matrix2[7]; result[10]=matrix1[2]*matrix2[8]+ matrix1[6]*matrix2[9]+ matrix1[10]*matrix2[10]+ matrix1[14]*matrix2[11]; result[14]=matrix1[2]*matrix2[12]+ matrix1[6]*matrix2[13]+ matrix1[10]*matrix2[14]+ matrix1[14]*matrix2[15]; result[3]=matrix1[3]*matrix2[0]+ matrix1[7]*matrix2[1]+ matrix1[11]*matrix2[2]+ matrix1[15]*matrix2[3]; result[7]=matrix1[3]*matrix2[4]+ matrix1[7]*matrix2[5]+ matrix1[11]*matrix2[6]+ matrix1[15]*matrix2[7]; result[11]=matrix1[3]*matrix2[8]+ matrix1[7]*matrix2[9]+ matrix1[11]*matrix2[10]+ matrix1[15]*matrix2[11]; result[15]=matrix1[3]*matrix2[12]+ matrix1[7]*matrix2[13]+ matrix1[11]*matrix2[14]+ matrix1[15]*matrix2[15]; } </code></pre>

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