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fabriciomicheli
08-27-2004, 12:23 PM
Hi buddies.
Im rendering an object and an error appears in the MR message window (take a look at the attached graphic).

Im using MR to test caustics in an object. That's my file config.

I have a torun knot with a Mental Ray material on it and a translucence lume shader in the surface slot. The scene is lit by an MR omni light and falloff is set for that light. I set a ground plane and the torus knot to generate and receive caustics, and in the MR render config I set on caustics and use a slow sampling (25) to get a preview.

When I render, that window appears. I don't know why? maybe the translucent lume shader doesn't support caustics...

I need some help :D

francescaluce
08-27-2004, 02:01 PM
this means that mentalray is shotting photons but that they doesn't hit any surface (allowed to 'receives' photons ) so to not waste time it stops the shotting at 10.000 photons.

If you think that the shotted photons are literaly bouncing in the scene you'll get a fast workaround.... doing a big sphere dome and set it to receiver/trasmitter... you'll effectively increase a lot the possibility that shotted photons are not missed in space but hit the surface with a secondary bounce... eventually increase the bouncing parameter.. this in general for GI.
for caustic never use an omni light but a spot light that 'points' the photons to the objects.. makes also sure you setup your mat as gen/rec photons.



ciao
francesca

fabriciomicheli
08-27-2004, 02:36 PM
Hey francesca... thanks a lot!
I got it all but the only thing I don't understand is how to set a MR material to generante and receive photons...
No idea

BTW, here's a test render. I don't see even one photon...

JeffPatton
08-27-2004, 03:18 PM
I don't know of a material that will generate 'actual' photons. You can use the glow(lume) or even an output map in combination with final gather to make an object glow. But that in itself doesn't generate photons for a GI calculation.

I have a couple of glow scenes on my MR page and one where I linked an omni light to some objects with a glow(lume) shader to allow the objects to emit photons if you want to have a look at those:

http://jeffpatton.net/Mental-ray.htm

JP

francescaluce
08-27-2004, 03:54 PM
I don't understand is how to set a MR material to generante and receive photons... ehy,, is not really that an obj generates photons (also if with mr you can do this with code..).. but transmits and receives.. I mean the mr flags you have in max under obj properties... generate and receives caustics..


edited: jeff, nice mr mats !!

ciao
francesca

fabriciomicheli
08-27-2004, 08:20 PM
many thanks to you guys
Well Jeff, Actually, the idea here was no to get a glow material, I just wanted to create something like wax or a material where I can see SSS, but I tried to achieve a decent effect not using the Parti Volume Photon Shader (like you use in your thread... what is great but it's a time killer you know). So I decide to use the Translucent Lume shader, but actually... I don't know how to use it correctly (The Lume help in MAX su***).
I just add it to the surface slot in a MR material, and assigned to an object. And I got the result I showed in the image I posted be4.
As u can see, I hoped to see some "caustic" effect in the ground plane (I mean, a kinda soft light) because in this case, it's just a flat opaque shadow, and it doesn't look real.
Or maybe a transparent shadow... (soft caustic effect)

I don't know how to achieve that effect man...
(BTW... your gallery is AMAZING! you're mastering Mental Ray)

:thumbsup:

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