"Bald Eagle" <cre### [at] netscapenet> wrote:

> So consider this:
>
> We take my idea of having an object registry, so we can store all of the objects
> in an array, and loop through them.
> Next, we loop through all the y and x of the camera view frustum, and use trace
> ()  to cycle through every object in the registry for every pixel.
> Using that <x, y, z> data, we have a map of the image with a sort of z-buffer.
> Now we write image data perhaps using a format like:
> <x, y, object1_z, . . . , objectN_z>
>
> What do you think?

Go, go, go ;) Maybe also get al the bounding boxes (min- max_extent) of the
object so one does not have to test every ray against every object. But, before
you know you are writing a ray-tracer within a ray-tracer, within a ray-tracer
....

POV-Ray has so many usable internal data that are not available to the user.
I've manipulated the radiosity proces by rendering an image with the radiosity
data from an other image. What if we knew the data file format and can
manipulate it? Or photon data? Normals, intersection points, mirror things, all
stuff that's available in OpenGL for shaders.

> Also, I've wanted a custom version of trace () that would return ALL of the
> intersections with an object, not just the first one, so we could do something
> like custom inside/outside tests using crossing numbers.
> Any idea on how to approach that via SDL that doesn't involve testing dozens of
> thin slices of the object perpendicular to the camera ray?

That is difficult as shapes can have all kind of holes and protrusions. What I
tried in the past is create a "slit camera" that works like a flat bed scanner,
but with the object rotating above the sensor.
https://en.wikipedia.org/wiki/Slit-scan_photography You could rotate such a
camera around the object and inside the object. Or make a point source camera
and scan in a sphere shape, but there will always be "self shadowing". Some of
these must be doable with the advanced camera features.

An other way could be to "shrink wrap" a mesh around an object and use the
vertices, but how in SDL?

ingo

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