On 3/12/23 13:41, Bald Eagle wrote:
> I also have a usage question with regard to orthographic:
> I did not seem to be able to get this particular inclusion of the "angle"
> keyword to work as described, but maybe I didn't try hard enough, or my camera
> {} block was malformed.

My only experience using orthographic & angle was first setting up a 
perspective view of solver test cases - where the camera needs be a 
significant distance away with smaller angles. Then I'd flip perspective 
to orthographic to get the, much harder for ray->surface equations and 
solver, ortho rays as another test case. For me all I did was flip the 
camera types... I've got no experience with more.

Where the documentation says:

"Note: The length of direction is irrelevant unless angle is used." is 
true only in an abstract sense. While not the direction vector length, 
the actual length of the ray in that direction absolutely matters with 
respect to how well many shapes work.

If I take my earlier Camera01z set up and change the location to be:

location <0,0,-2*1e3>

I get the attached image of the same identical scene. The ray length 
went from ~2 to ~2000.

Bill P.

(a) - To some extent it matters to other camera types(b) (or say light 
positions for shooting photons), but in other cases the rays are almost 
all coming in at some angle relative to the scene objects - and this 
alone helps the ray->surface equations set up and the solvers.

(b) - I had too sovler tests for extremely small angle perspective 
cameras 1-2 degrees and these too often turn up equation set up / solver 
issues both because the camera rays are nearing orthogonal, but also due
the length.

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