On 1/19/2025 12:33 PM, William F Pokorny wrote:
> Ref:
> 
> https://news.povray.org/povray.binaries.images/thread/ 
> %3C678b9010%40news.povray.org%3E/
> 
> Playing more with matrix transforms mixing shears (and by side effect 
> rotation) led to the attached animation.
> 
> The entire animation part of the set up was:
> 
>      matrix <
>          1.0, (frame_number-1)/60, 0.0,
>         -(frame_number-1)/60, 1.0, 0.0,
>          0.0, 0.0, 1.0,
>          0.0, 0.0, 0.0>
> 
> Then using +kff480 on the command line to render 480 frames.
> 
> There is a 'scale 1/6' of the checker pattern following the matrix 
> transform in the base scene - which is slowly countered as the frame 
> number increases.
> 
> I don't 'really' understand what's happening in total. In any case, it's 
> cool, though, not as trippy as Josh's earlier post. :-)
> 
> Bill P.

Very cool. I'm very rusty on matrices. My guess is the smooth rotation 
(I'm assuming the camera is not rotating at all here, or the plane, 
other than what the matrix is doing) comes from the fact that the first 
two groups of the transform matrix are orthogonal, so it rotates instead 
of shears. The scaling happens because the first two "vectors" aren't 
constrained to the unit vector.

Or did I misunderstand what you meant by "I don't 'really' understand 
what's happening...' and just talk down to you by accident?

I had thought about shearing my meshes in the camera, so I will have 
work on that sooner rather than later.

Josh

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