Alternative to Global Illumination and Final Gather

[Thapa_Laxman]

Tutorial for mental ray (3ds Max version)
Occlusion is a fast and simple method to simulate the effects of global illumination. Occlusion is the extent to which the area above a point is covered by other geometry. This is achieved by tracing a number of probe rays inside the hemispherical area above the point and testing to what extent this region is blocked.

[Thapa_Laxman]

This occlusion effect can be generated by using Ambient/Reflective Occlusion or Dirtmap Shader 1.20 written by Daniel Rind Download DirtMap (http://animus.brinkster.net/downloads/Dirtmap.zip). Now you have to get a declaration file for this shader too, because the author only provides one for Maya. UMXPrime has written one for max, download it here (http://perso.wanadoo.fr/ronchin.basket/umxprime/tutorials/AO/files/dirtmapMI.zip)

Installation of dirtmap 1.20 shader:
• Extract all files to X:\3dsmax7\mentalray
• Copy UMXPrime’s Dirtmap.mi to X:\3dsmax7\mentalray\shaders_autoload\include and also to X:\3dsmax7\mentalray\Dirtmap\nt-x86\contents
• Copy Dirtmap.dll to X:\3dsmax7\mentalray\shaders_autoload\shaders
Launch 3ds Max
• Assign mental ray as your renderer
• Open material editor and assign Dirtmap or Ambient/Reflective Occlusion in self-Illumination slot. For Strauss material put the map in Color slot and for Raytrace material put the map in Extra Lighting.

[Thapa_Laxman]

Sky color is controlled through Environment > Common Parameters > Background > Color

[Thapa_Laxman]

Ambient/Reflective Occlusion Setting


For test render
• decrease samples, say 8
• decrease Spread
• Increase Max distance

[Thapa_Laxman]

Dirtmap 1.20
For test render
• Decrease Ray Spread (In above image decreasing this value to 80 decreased the render time by 9 seconds with similar image quality.)
• Decrease Samples and Far Clip


* Enable Invisible to Sec. Illumination if you are using GI and Final Gather to decrease render time.

[Thapa_Laxman]

References:
Ambient Occlusion (http://www.neilblevins.com/cg_education/ambient_occlusion/ambient_occlusion.htm)
Another Tutorial (http://perso.wanadoo.fr/ronchin.basket/umxprime/tutorials/AO/index.htm)

[Thapa_Laxman]

106 views and no replies!!!!!.
Is it useful to anyone? or shall I remove.
Any comments are welcome.

[Mr. Bluesummers-3DT]

Quick Reply
Looks nifty to me, but I use 3dsm6. Moreover, I rarely use the dirtmap...map because it runs slow for me for some reason. Usually if I need GI like effects I'll do finalgather, which usually runs quickly enough that I'm a happy camper.
Neat technique though!

[I3ear17]

NO!!! Please don't remove it! I have been studying it but haven't had time to try it at work. I put the files in the folders you said, but when I go to select them I have problems.
---Open material editor and assign Dirtmap or Ambient/Reflective Occlusion in self-Illumination slot---
I am not finding those selections. I am using Max6. Does the shader show up in the material selection list?

[Thapa_Laxman]

I think you didn't assign mental ray as the renderer. You need mental ray to use Ambient/Reflective Occlusion or Dirtmap Shader.

[I3ear17]

nope, i didn't read your post well enough, i downloaded the Maya plugin, not the max one. I will try again

Also, i guess I should ask will this even work with Max6?

[Thapa_Laxman]

Finally a neat trick is to use the shader as a light shader on an omni light. Simply instance the shader into the lights LIGHT SHADER map, and turn on only its "Ambient" contribution under the "Advanced Effects" rollout. This will effectively make the occlusion shader into a scene wide occlusion shader that will shade all scene objects. And also you don't have to assign these shaders in self illumination slots.
Here is a test renders:-

[ahmed_shalaby]

the version of max is corrupted hope u check it and thank u very much for ur thread