RenderMan & RISpec, 3Delight: indirectdiffuse()

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RenderMan & RISpec >> 3Delight: indirectdiffuse()

by Giuseppe Randazzo » Thu, 20 Oct 2005 03:02:58 GMT

Hello to all,
I'd like to use the indirectdiffuse() shadeop
of 3dl, but I don't have any example to start.
Is it possible with this function to obtain nice
GI effects like VRay or Maxwell renderer?
(and without multiple photon map/beauty pass like Prman/pixie ?)
I tried in a naive attempt like this..

surface
indirect( float Ka = 1, Kd = 1; float samples=32)
{
normal Nf;
Nf = faceforward( normalize(N), I );
Oi = Os;
Ci = Cs * ( Ka*ambient() + Kd* indirectdiffuse(P, Nf, samples) );
Ci *= Oi;
}

.. with a directional light as main light source.
all surfaces was marked for "trace",
but ALL was solid black!..
..hem I doubt that something could be wrong.. :)
Any help?
thanks in advance.

G.




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RenderMan & RISpec >> 3Delight: indirectdiffuse()

by owenr » Sat, 22 Oct 2005 03:23:51 GMT


Hi Giuseppe,

In case you don't know, 3Delight now recognizes the Ns (shading normal
of the surface being illuminated) variable inside light shaders, so you
might want to try indirectdiffuse() in a light shader to automatically
produce colour bleeding when standard surface shaders, such as "matte",
are used.

However, there is a valuable lesson to learn here in your experiment
with indirectdiffuse() in a surface shader.
You say the scene contains one lightsource, a directional light.
I will make an important assumption that you are attaching the
experimental shader to all geometry in the scene.
The shader provides no self-illumination and has no function, such as
diffuse(), to gather direct illumination from the lightsource, so
nothing will be illuminated by your directional light, so there will be
no light to be gathered by the indirectdiffuse rays, so all objects
will be rendered black.
One solution is to change:
Ci = Cs * ( Ka*ambient() + Kd* indirectdiffuse(P, Nf, samples) );
to:
Ci = Cs * ( Ka*ambient() + Kd*(diffuse(Nf) + indirectdiffuse(P, Nf,
samples)) );

I hope that's right because I don't have 3Delight installed at the
moment.

Owen
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RenderMan & RISpec >> 3Delight: indirectdiffuse()

by Giuseppe Randazzo » Sat, 22 Oct 2005 07:46:57 GMT

Hi Owen,
Your explanation has been precious!
I'm running now a test render with the modified shader
and it works well!! 3Delight is fast and with a low
grain level, I will implement the light version,
thanks again,

Giuseppe
///////////////////////////////////////////////////
surface
indirect( float Ka = 1, Kd = 1; float samples=16;)
{
normal Nf;

Nf = faceforward( normalize(N), I );

Oi = Os;
Ci = Cs * ( Ka*ambient() + Kd*(diffuse(Nf) + indirectdiffuse(P, Nf,
samples)));
Ci *= Oi;
}
///////////////////////////////////////////////////


"owenr" < XXXX@XXXXX.COM > ha scritto nel messaggio
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