Thorsten Froehlich <tho### [at] trfde> wrote:
> May I suggest you check out the books listed in the documentation for
> understanding the algorithms used in POV-Ray? It is not like the algorithms
> were conjured up by the POV-Team from thin air ;-) Well, actually some were,
> but that is another story...
>
> There is plenty of other ray-tracing literature out there, too. If you need
> well-annotated ray-tracing source code, I would recommend the book
> "Physically Based Rendering", which explains pretty must everything there is
> necessary to know.
>
> Grown source code like that in POV-Ray is not particularly suited to learn
> the basics of ray-tracing. Books are much better for that :-)
>
>  Thorsten, POV-Team



Thanks for your suggestion. Actually I am trying to study the version 3.6.0 of
POV-ray for windows for my undergraduate thesis and I know the basics of ray
tracing already. I am afraid I do not have much time to go through all the
suggested reading because my deadline to submit the thesis is very near. I have
read other books and online materials. I was able to understand many of the
algorithms. My appologies for bothering you with my simple questions but it
would help me greatly if you answer the question. I have spent quite a lot of
time trying to figure it out.


My question is, these are the defined values of left, right, top and bottom
plane normals and distances for polygon clipping.

/* Planes for 3d-clipping. */

const VECTOR VIEW_VX1 = {-0.8944271910, 0.0, -0.4472135955};
const VECTOR VIEW_VX2 = { 0.8944271910, 0.0, -0.4472135955};
const VECTOR VIEW_VY1 = {0.0, -0.8944271910, -0.4472135955};
const VECTOR VIEW_VY2 = {0.0,  0.8944271910, -0.4472135955};
const DBL VIEW_DX1 = 0.4472135955;
const DBL VIEW_DX2 = 0.4472135955;
const DBL VIEW_DY1 = 0.4472135955;
const DBL VIEW_DY2 = 0.4472135955;

They are passed to Clip_Polygon to clip the sides of bounding volumes when all
of its points are not inside the viewing volume. I understood the clipping
algorithm but, where is the origin of these vectors? I think it is in the
middle of the projection plane.


I have to draw pictures to explain the algorithm. So, please answer the
question.

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