View Full Version : mia_physicalsun and caustics
06-13-2007, 11:52 PM
I have read through the manual and havenīt seen anywhere wheather mia_physicalsun casts caustic photons or not. It seems like it doesnīt. Iīm rendering some architectural stuff where I have mia_material with the glass pane preset on the ordinary windows. However, there are some constructions made of thick solid glass so I thought that those glass panes should be solid models and apply physical glass (also mia_material preset) onto them. The shadows does not become transparent. The manual says that you need caustic photons so is it possible to turn those on in physicalsun?
06-14-2007, 03:22 PM
Yes it is.
Find the 'sun' directional light and turn on Caustics, and enable it also in Render Settings.
Try to set the bounding box that encompasses Your scene, though, because without it, photon emission might hit insane times.
Also, You have to check if Your solid glass mia-material is connected to it's SG's photon and shadow shader slots.
06-14-2007, 03:38 PM
Oh, I thought you shouldnīt touch the directional light other than rotating it, so I looked for a caustic feature in the physical sun node. Thanks, I will try that right away.
06-15-2007, 06:26 AM
No, didnīt work. What does happen when I turn on the photons on the directional node? Is the photon intensity still calculated by the physical sun? And the amount of emitted photons? Or do I have to adjust the values manually?
"You have to check if Your solid glass mia-material is connected to it's SG's photon and shadow shader slots". Recently I noticed that I have two SGīs for each mia_material.
This is what I do: I assign a Maya shader, in this case a Blinn, to a 3d model that is a thick glass plane. Then I connect a mia_material to miMaterialShader, miShadowShader and miPhotonShader to the Blinn SG. If I select the mia_material and show inputs/outputs in the Hypershade window I see that there is another SG. Itīs only connected to the miMaterialShader. Do I ever have to mess with that SG as well?
06-15-2007, 09:58 AM
You can directly assign the mia_shader to your mesh, without any maya node.
And if you check the automatic photon energy in the physicalSun parameters you donīt need to touch the paremeters in the light. But you must switch on the photon emisson on the light.
06-15-2007, 01:15 PM
Is the photon intensity still calculated by the physical sun? And the amount of emitted photons? Or do I have to adjust the values manually?
Photon number is inherited from 'sun' lightShape node - so You set the number there.
In Render Settings You have to enable Caustics, otherways it won't do anything. And as octane62 said - You have to also enable photon emission in 'sun' lightShape.
You don't need blinn or any other material, except mia_material, plugged in all 3 afore mentioned slots of it's SG.
Last step is to check on 'Refractive Caustics' under "refraction' tab of Your glass mia_material.
That should pretty much be it.
06-15-2007, 06:05 PM
Well, it kind of works. I made a simple scene for testing with a plane as ground and a thin cube as a glass plane. I assigned a mia_material with physical glass preset to the glass plane. Everything works if I add a spotlight to the scene with photons and caustics on - a nice transparent shadow. But it doesnīt work with physical sun. I get a dark blueish and almost solid shadow. I guess that physical sky & sun are for large scenes where you never get close to details. Thatīs because I get other problems as well like very spotty renders at close-ups - no matter how I tweak accuracy, radius, amount of photons or add a bounding box to the physical sun, increasing FG points etc. Well, thank you anyway. I think I have to rig a second lighting setup when I really have to get accurate glass renders or close-ups.
06-15-2007, 06:05 PM
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