Am 01.12.2014 22:38, schrieb ediem:
> Dear all,
>     I am a new member and I have a question about perspective projection. In
> particular I would like to insert the matrix given at this link
> http://www.cs.princeton.edu/courses/archive/fall99/cs426/lectures/view/sld029.htm
> and use this matrix to transform some objects but apparently it's not possible
> since POVRay assumes that the last row of the transformation matrix is always 0
> 0 0 1 (and hence is not written). Is there any workaround ?
>     Thanks in advance
>       Edie

Um... no; actually, POV-Ray only does affine transformations; 
perspective projections aren't affine, and actually this habit of 
cramming the parameters for a perspective projection into a 4x4 matrix 
requires some "creative" re-interpretation of the matrix data (that is 
to say, it's a hack), and therefore frequently leads to misunderstandings.

Perspective projection can /not/ be performed by applying a standard 
vector-matrix multiplication.

(Actually, even the use of matrices for non-linear affine transformation 
in 3D space is a hack, using an extension into 4D-space, but at least 
the transformations from 3D to 4D and back from 4D to 3D are as trivial 
as can be.)

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