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 CAD / Ray-Tracing / 501
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Subject: 
Re: L3P / POVRay material questions
Newsgroups: 
lugnet.cad.ray
Date: 
Sat, 26 Aug 2000 13:53:45 GMT
Viewed: 
656 times
  
Sproaticus skrev i meddelandet ...
In lugnet.cad.ray, Anders Isaksson writes:
{...]
The important thing here is that I do not put a light inside a brick, but
declare a light which 'looks_like' the brick, and putting this in the model
instead of the original brick. I'm also using a special color, to be able to
experiment with the different parameters.

Thanks!  :-,  But I had trouble positioning the light_source; it wouldn't be
rotated and translated like an object.  Did you have to figure out the
coordinates all over again?

No, I just used the light object instead of a brick object, using the same
matrix.
Example (long lines):

// object { _179_dot_dat matrix <1-SW/20,0,0,0,1-SW/12,0,0,0,1-SW/20,0,SW/6,0>
matrix <1,0,0,0,1,0,0,0,1,330,-88,-170> #if (version >= 3.1) material #else
texture #end { Color46 } }

replaced by:

object { light_point matrix   <1-SW/20,0,0,0,1-SW/12,0,0,0,1-SW/20,0,SW/6,0>
matrix <1,0,0,0,1,0,0,0,1,330,-88,-170>}

BTW, any chance of seeing the .POV for your scene?

Of course, I can mail it to you if that's OK? (It's 619K !! unzipped but
probably much smaller when compressed - is there a lugnet.attachments?)

The fourth value for an 'rgbf' is the transparency. The reflection values
might also need some twiddling.

Is that rgbf or rgbt?  What's the difference between "f" and "t"?

<rgbF> Beats me. I just search the POV scene language documentation and find
something which I try. Now you've forced me to read through it again &%#&
...
OK, I looked it up, and the F means 'filter', T 'transmit', and you can
combine all of it into a five parameter rgbFT <r, g, b, f, t> if you want.

<quote from docs>

The 4th component, called filter, specifies the amount of filtered
transparency of a substance. Some real-world examples of filtered transparency
are stained glass windows or tinted cellophane. The light passing through such
objects is tinted by the appropriate color as the material selectively absorbs
some frequencies of light while allowing others to pass through. The color of
the object is subtracted from the light passing through so this is called
subtractive transparency.

The 5th component, called transmit, specifies the amount of non-filtered light
that is transmitted through a surface. Some real-world examples of
non-filtered transparency are thin see-through cloth, fine mesh netting and
dust on a surface. In these examples, all frequencies of light are allowed to
pass through tiny holes in the surface. Although the amount of light passing
through is diminished, the color of the light passing through is unchanged.
The color of the object is added to the light passing through so this is
called additive transparency.

</quote>

So it really sounds like rgbF is what we want.

HTH,
--
Anders Isaksson, Sweden
BlockCAD:  http://user.tninet.se/~hbh828t/proglego.htm
Gallery:   http://user.tninet.se/~hbh828t/gallery.htm



Message has 1 Reply:
  Re: L3P / POVRay material questions
 
(...) Awesome! Thanks! :-, (...) Sure, I'm okay for disk space right now. I dunno about Todd hosting a large file; Brickshelf might be the perfect place for that. (...) :-, (...) Arg. I never did well with these docs; their real-world examples help (...) (24 years ago, 29-Aug-00, to lugnet.cad.ray)

Message is in Reply To:
  Re: L3P / POVRay material questions
 
(...) Thanks! :-, But I had trouble positioning the light_source; it wouldn't be rotated and translated like an object. Did you have to figure out the coordinates all over again? BTW, any chance of seeing the .POV for your scene? (...) Is that rgbf (...) (24 years ago, 25-Aug-00, to lugnet.cad.ray)

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