Mental Ray render elements problem...

[jfmonod]

Hi,

I'm using Max 2009 and am having a problem rendering out my shadows, diffuse ... etc to seperate files with "Render Elements" in Mental Ray. Specifically I end up with a bunch of black image files. "Shadows" does not contain any information at all and "Diffuse" shows bits of distorted false color image which looks like half of a scanline render but using mental ray materials. Z depth is coming out ok.

What I don't get is that my scene renders fine otherwise. Everything's there and shadows are fine. it's just when I try to split it up for compositing that the rot sets in.

I have an exterior scene with a Mr Daylight system, final gather, render elements (diffuse, shadow, z depth) on and filter on. I have tried output to tif & png with no effect.

Geometry is exported from Revit and uses Arch & Design materials.

Also, how does one render out individual elements in MR without having to render the entire image ?

Any help would be much appreciated as always : )

Many thanks,

JF

[frank1331]

Look at this link. It should help with the compositing you are working on.

 

http://www.aecbytes.com/tipsandtricks/2007/issue21-Compositing3D.html

[jfmonod]

: ) That's actually what got me into this mess in the first place. I found that article (I have it printed out in front of me as we speak) and thought that I had finally found the Holy Grail. Turns out that it's another one of those "Push this button and it just works" things. Except when it doesn't.

I think that my problem is that the article talks about scanline rendering and I have MR lights and materials. The only MR render in here is the ambient occlusion material override. Oh and that doesn't work for me either by the way.

[odouble]

It does not matter what renderer you choose when you with the tutorial. It should work just fine. Mentalray is simply "outputing" information (From internal floating point data) based on your render settings which is then converted to your chosen format to be used in your compositing package of choice.

 

That being said you are probably overlooking something. Your shadow element is supposed to come out black. When you saved your render elements to the tiff format did you make sure to check the "store alpha channel" option? If you did not you will have no alpha channel to select and invert to composite a shadow layer. I suspect this is your problem.

You can also render out in openEXR directly and you would not have to do the invert alpha thingy as in the tiff format.

 

I think you skipped a step somewhere.

[jfmonod]

odouble... you nailed it. I am now going to go and sit in the corner.

[odouble]

Hey, glad I could help.