William F Pokorny <ano### [at] anonymousorg> wrote:


> The benefits of (2) depend on:
>
> a) how much void space there is between that outer cylinder and all the
> inner per segment ones.

Yes, that is a better way to express what is going on.

> b) the alignment of rays with the bounding box used for global bounding.
> I looked too at completely eliminating the initial cylinder bound test
> as we already do cylinder bounding for each segment / interval.

I was having some troubles getting my endcap intersection tests to work
properly.
I think in the pre-work absorbing coffee phaze/haze that I figured out half of
that.

The second half may be directly related and solved by that realization.

So at present, I believe that I have code that reliably tests for intersections
with the infinite cylinder, and once I fix the issue with the end caps, then I
will begin to run some comprehensive tests. (*)

After that, I can either let you look over and test the code on your own, or I
can work on plugging it into the Section 3.9 raytracer as a function call.

https://wiki.povray.org/content/Documentation:Tutorial_Section_3.9#The_idea_and_the_code

- BW

(*)  I have made a list of 16 different types of rays to test, and want to
parameterize them so that I can just auto-calculate rays for any cylinder
parameters I enter.

(1) Ray parallel to cylinder axis, which misses the cylinder
(2) Ray that is skew/perpendicular to cylinder axis which misses the cylinder
(3) Ray parallel to cylinder axis, which intersects the cylinder edge
(4) Ray that is skew/perpendicular and that intersects tangentially
(5) Ray parallel to cylinder axis, which intersects the cylinder inside
(6) Ray that is skew/perpendicular and that intersects inside
Diagonal rays that:
(7) hit the bottom end cap, then the top end cap (non-perpendicularly)
(8) hit the cylinder then the bottom end cap
(9) hit the top end cap then the cylinder
(10) hit the cylinder then the top end cap

(11) Ray that is parallel to bottom end cap and misses
(12) Ray that is parallel to bottom end cap and intersects
(13) Ray that is parallel to top end cap and misses
(14) Ray that is parallel to top end cap and intersects
(15) Ray that clips a bottom corner
(16) Ray that clips a top corner

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