Hi there...I really love this app. I've been using computers for 35 years,
and it's been
a long time since I've wanted to go over every speck of the docs, and get
into all the
dark corners.

I have a couple of newbie questions, though, that I haven't had much luck
finding answers
for:

1) Pointers (links, etc) to info and approaches for using POV-Ray as a
virtual optics
    bench. Not asking the app to perfectly model optics--I just want to do
simple stuff. Example:
    I'm converting a parabolic satellite dish into a solar collector. I want
to place a secondary
    reflector just short of the focal point, and redirect the resulting beam
down through the
    axis of rotation. So this is all front-surface reflection, and I'd like
to look at the result of
    SORs for the secondary reflector before building something. I think I
can create an array
    of multiple-parallel-beam light sources (array of laser beams), so I can
look at the path of
    each beam through the system.

    So in this context (other than requesting general info on optics
projects in POV-Ray), is
    there a way to "blow smoke" in the air to see each beam without
attenuating it?

2) This is the more serious question. I'd like to model an object (for
example, the union of
    two extruded splines that are centered and parallel to the z-axis), take
cross-sections of
    the object at intervals, and read each cross-section out into a file so
the dataset can be converted
    into commands for a numerical-control milling machine. This is more for
artistic applications,
    so extreme precision isn't needed.

    So far, I've discovered only two possible methods, both of which are a
little kludgy:

    -- Derive the union of the shape and an intersecting plane, and using a
parallel light source
    project the slice onto a "screen" of sorts that is coincident with the
POV of the camera. Save
    the bitmap, and then use a conversion utility to read out the outline.
Very kludgy, but creative, no?

    -- Use POV-Ray's _inside_ function to determine if a given point is
inside or outside the
    object. Use an interative routine that "scans" along an array of XY
points on each z-plane
    cross-section, and then by successive approximation generate a series of
points that are
    just inside (or outside) the surface up to some limit of accuracy.

    I can see that I can generate a mesh, save the surface to a file, and
take cross-sections of that
    dataset, but I was wondering if there was a more generalized method one
could use with any
    given union of objects.

Thanks for at least reading this far! 8)

--Chris

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MVSmith nous apporta ses lumieres ainsi en ce 2004/01/21 20:50... :

>Hi there...I really love this app. I've been using computers for 35 years,
>and it's been
>a long time since I've wanted to go over every speck of the docs, and get
>into all the
>dark corners.
>
>I have a couple of newbie questions, though, that I haven't had much luck
>finding answers
>for:
>
>  
>
Possible using "photons" and scathering media. Set the media to zero 
absorbtion and set some scathering. The render will take a long time as 
both photons and media will add a lot of computation. (look at 
"optics.pov" in scenes/advanced)

>1) Pointers (links, etc) to info and approaches for using POV-Ray as a
>virtual optics
>    bench. Not asking the app to perfectly model optics--I just want to do
>simple stuff. Example:
>    I'm converting a parabolic satellite dish into a solar collector. I want
>to place a secondary
>    reflector just short of the focal point, and redirect the resulting beam
>down through the
>    axis of rotation. So this is all front-surface reflection, and I'd like
>to look at the result of
>    SORs for the secondary reflector before building something. I think I
>can create an array
>    of multiple-parallel-beam light sources (array of laser beams), so I can
>look at the path of
>    each beam through the system.
>
>    So in this context (other than requesting general info on optics
>projects in POV-Ray), is
>    there a way to "blow smoke" in the air to see each beam without
>attenuating it?
>  
>
Look for "trace.pov" in scenes/language. It use the "math.inc" library. 
It contain a function that return the intersection point of an object 
and a vector.

>2) This is the more serious question. I'd like to model an object (for
>example, the union of
>    two extruded splines that are centered and parallel to the z-axis), take
>cross-sections of
>    the object at intervals, and read each cross-section out into a file so
>the dataset can be converted
>    into commands for a numerical-control milling machine. This is more for
>artistic applications,
>    so extreme precision isn't needed.
>
>    So far, I've discovered only two possible methods, both of which are a
>little kludgy:
>
>    -- Derive the union of the shape and an intersecting plane, and using a
>parallel light source
>    project the slice onto a "screen" of sorts that is coincident with the
>POV of the camera. Save
>    the bitmap, and then use a conversion utility to read out the outline.
>Very kludgy, but creative, no?
>
>    -- Use POV-Ray's _inside_ function to determine if a given point is
>inside or outside the
>    object. Use an interative routine that "scans" along an array of XY
>points on each z-plane
>    cross-section, and then by successive approximation generate a series of
>points that are
>    just inside (or outside) the surface up to some limit of accuracy.
>
>    I can see that I can generate a mesh, save the surface to a file, and
>take cross-sections of that
>    dataset, but I was wondering if there was a more generalized method one
>could use with any
>    given union of objects.
>
>Thanks for at least reading this far! 8)
>
>--Chris
>
>
>
>  
>
Alain

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