Shear camera frustum

num3ric · October 13, 2015, 3:40pm

Here’s how this is handled in cinder:

cinder/Cinder/blob/master/src/cinder/Camera.cpp#L310

      
        
            	}
            
            
	if( mLensShift.x != 0.0f ) {
            		mFrustumRight = ci::lerp<float, float>(2.0f * mFrustumRight, 0.0f, 0.5f - 0.5f * mLensShift.x);
            		mFrustumLeft = ci::lerp<float, float>(0.0f, 2.0f * mFrustumLeft, 0.5f - 0.5f * mLensShift.x);
            	}
            
            
	mat4 &p = mProjectionMatrix;
            	p[0][0] =  2.0f * mNearClip / ( mFrustumRight - mFrustumLeft );
            	p[1][0] =  0.0f;
            	p[2][0] =  ( mFrustumRight + mFrustumLeft ) / ( mFrustumRight - mFrustumLeft );
            	p[3][0] =  0.0f;
            
            
	p[0][1] =  0.0f;
            	p[1][1] =  2.0f * mNearClip / ( mFrustumTop - mFrustumBottom );
            	p[2][1] =  ( mFrustumTop + mFrustumBottom ) / ( mFrustumTop - mFrustumBottom );
            	p[3][1] =  0.0f;
            
            
	p[0][2] =  0.0f;
            	p[1][2] =  0.0f;
            	p[2][2] = -( mFarClip + mNearClip ) / ( mFarClip - mNearClip );