Decompose projection matrix44 to left, right, bottom, top, near and far boundary values

android, opengl-es, qcar-sdk

Solution

Here are the resolutions of the equation systems Christian Rau referred to :

For an orthographic matrix :

near   =  (1+m34)/m33;
far    = -(1-m34)/m33;
bottom =  (1-m24)/m22;
top    = -(1+m24)/m22;
left   = -(1+m14)/m11;
right  =  (1-m14)/m11;

For a perspective matrix :

near   = m34/(m33-1);
far    = m34/(m33+1);
bottom = near * (m23-1)/m22;
top    = near * (m23+1)/m22;
left   = near * (m13-1)/m11;
right  = near * (m13+1)/m11;

You can replace the values m11, m12, etc., by the formulas defined in the documentation for glOrtho and glFrustum to check it's correct.

Problem

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