Raytracing Shadows and Fog

# 1 06-05-2004 , 12:40 PM

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Join Date: Jul 2003

Posts: 19

Hello Everyone

I have started with light fog exercise and I came up with a problem as you will see in the image bellow. I created a polygon box. I extruded one of the face to make a hole in it and then created a second floor (see wireframe caption). I wanted light to go through the hole but I wanted to have some fog as well as shown in the Depth Map Shading caption. Si I used Raytracing Shadow in my spotlight and activated the Light Fog Effect. When rendered I see the light that goes through the hole but no fog comes along (see caption Raytracing Shadow). But I know there is fog because you can see it in the Raytracing Shadow caption. For some reason, the hole is bloking the fog in Raytracing Shadow while in Depth Map Shadow it let it go through.

I want to avoid having 4 pieces of polygon to create the floor and have a hole in it. Does anyone have any idea?

Thanks
Salsero

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# 2 07-05-2004 , 06:10 PM

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Join Date: Jul 2002

Posts: 1,253

i am not clear about he shadow stuff but regarding the hole thingie.... try using the boolean operations... should work

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# 3 29-03-2011 , 06:12 PM

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Join Date: Mar 2011

Location: Brasil

Posts: 2

me too am with this problem

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# 4 29-03-2011 , 09:11 PM

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Join Date: May 2003

Location: London

Posts: 1,001

The problem isn't the hole, maya light fog volumes only work with Dmap shadows due to how Dmap are calculated. Essentially the volume is calculated at the same time as shadows are cast.

If your raytracing and want a fog volume in mental ray. you need to create a cube or any primative large enough to contain your fog volume in, assign a transmat shader to it, then assign a parti_volume to the volume shader on the shading group, give the color of the volume something not black and it should work.

If you go into mental ray features you might have to tweak around some settings to make it work if your camera is inside the fog bounding volume, not too sure.

This way the light will do ray marching calculations on the volume and will be visible in your renders.

Also avoid booleans... they are very messy unless your mesh is quite clean and its easy to clean up, IMO more problems than its worth.

FX supervisor - double negative

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