View Full Version : Odd Color caustic/dielectric material help

10 October 2005, 02:53 AM
Hello everyone,

So I have been messing around in mental ray trying to get a photo real render and here is what I have so far.
First of all suggestions to help it look more real. Second, what is up with the caustic in the shadow. Why is green? Also, the vase it too transparent, how do I make it more opaque. oh, btw the vase has lambert material with a dielectric material and dielectric photon material mapped to the SG. I'm not so familiar with these shaders (the two dielectric materials). But anyways, thanks in advance.

10 October 2005, 08:16 AM
hmm firstly, in order to get physical correct caustic intensity, do this:
* disable every Indirect Illumination metod first (aka GI or FG)

* on the light that emits caustic photons, in the mentalray section of the AttributeEditor, enable the "Area Light" option (this gives a much realistic ilumination) and then click on the Custom Light Shader map-button. When the CreateRenderNode window popups, find the physical_light mentalray shader (it's in the mentalray lights section) and click it to make the connection. Now, open the physical_light's AttributeEditor and adjust it's Color Value ( V from HSV) until you get the desired direct light intensity. (you'll need to render several times until you're satisfied with the intensity; btw to change the lights color, adjust the Hue and Saturation for the physical_light.Color)

* once you get the right intensity, re-enable the GI/FG in the Render Globals window and then copy the physical_light.colorV onto the Photon Intensity attribute of your light to get the physical caustic intensity

ok now you may want to check these awesome mentalray custom shaders:

* -- an awesome glass shader, much better than the dielectric one ;)

* -- get the ctrl_shading 1.2 shader wich is an unbelieveble awesome and powerfull shader wich does most types of shading you need (phong, orennayar, lambert, frensel, etc and supports ultra fast glossyness :))

* -- get the mix8layer shader wich is great for mixing and is also needed to make the ctrl_shading work (actually you need any passtrough or in maya 7 you need neither)

* -- an very good camera lens shader (supports fast physical DOF and many other lens types)

btw if you don't know how to install these shaders check this out

so for the glass assign the l_glass shader to both photon and material slots of your SG (check deathfall ( for some video tutorials on l_glass) and for everything else, use the ctrl_shading material in conjunction with an mib_photon_basic (for basic photon this is ok).

PS. don't connect the ctrl_shading directly to the material slot of the SG (you'll get a crash if you do so :D). Instead, connect the mix8layer to the material slot and then plug the ctrl_shading.compound into the mix8layer.f_layer0 (or smth similar :)) and also set the number of layers to 0


10 October 2005, 01:35 AM
Thanks for your help. I will try your sugestions. But as for the shaders, they all seem to be Windows only, are there any mac builds out there?

10 October 2005, 03:15 AM
So, here is an updated render using the area light option and the physical light shader for the light shader.

As noted before I was unable to use the other shaders as they appear to be PC only :sad:

Also the other thing, the render time is starting to get LONG, 44:56 for this past render, 640x480. Any sugestions to help with this?

And on a completly unrelated note, why do my in the post images not embed? You can see the code I am using to embed the image. What am I doing wrong?

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10 October 2005, 03:15 AM
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