[Radiance-general] Antimatter

[Jack de Valpine]

Hi Giovanni,

It was great to meet you at the workshop. Thanks for making the trip 
over to the states!

It has been awhile since I did anything with antimatter but here is an 
example that should work:

void plastic white
0
0
5 1 1 1 0 0

void plastic red
0
0
5 1 0 0 0 0

void antimatter am
2 red white
0
0

!genbox white wall 10 .1 10

!genbox am holes 1 1 1 | xform -t -.5 -.5 -.5 -t 1 0 5 -a 5 -t 2 0 0

This will make five holes in the "wall" geometry, where the holes are 
cut will be red.

The main trick here is understanding the antimatter material definition

void antimatter <name>
2 <mod1> <mod2>
0
0

where I think of it as "make a hole using material <mod1> in material 
<mod2>." If you do not want there to be any material where the hole is 
cut then mod1 can be void.

At first I was thinking that this only works on "volumes" rather than 
surfaces. But a quick test shows that it does work on surfaces as well:

white polygon wall
0
0
12
0   0   0
10   0   0
10    0   10
0   0   10

!genbox am holes 1 1 1 | xform -t -.5 -.5 -.5 -t 1 0 5 -a 5 -t 2 0 0

NOTE however that if you want to punch holes in planar surfaces then 
<mod1> needs to be "void" in the antimatter definition.

Hope this helps,

-Jack de Valpine

-- 
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# president
#
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#
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Giovanni Betti wrote:
> Dear All,
>
> It has been a real pleasure to have the chance to be at the radiance
> workshop in Cambridge and to meet all the great guys there and to listen
> to so many inspiring presentations (btw, really looking forward to see
> them on line!)
>
> Now back to the office and again fighting with day to day issues. I am
> trying to model a series of openings in a screen using antimatter and I
> am getting really confused.
> The screen is modelled as a single surface intersected by a number of
> cubes. As in the antimatter description I read:
> "The viewpoint must be outside all volumes concerned for a correct
> rendering." I assume that means that the camera should not be inside one
> of the cubes and that (I guess) the cube normals should point outward. 
> Done that, I am able to see through the cubes but I do not see the
> pattern of light coming through the antimatter holes, I just have a big
> solid shadow...
>
> Is that how it is supposed to behave? Does anybody have any clue about
> what I am doing wrong?
>
> Thanks in advance,
> Best,
>
> Giovanni
>
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