View Full Version : Render Layer Display Issue

10 October 2011, 05:44 PM
I'm figuring out how to set up render layers in Houdini and need some help. For example, I want to hide my main geometry but have it's occlusion show up on the ground. Similarly, if I wanted to render not the ground plane but the reflection from it onto my main piece of geometry. How in the heck do you do this in Houdini? Such a basic task but I don't know where to look.

The only parameters I found is display, check on or off in render and the display tags. I need help soon. Thanks.

10 October 2011, 06:22 PM
What I was looking for is Phantom. It's in the geometry parameter list under Render.

10 October 2011, 03:48 PM
What I was looking for is Phantom. It's in the geometry parameter list under Render.
Also check out Objects Tab of Mantra ROP, where you can overwrite some of render parameters of rendered objects without touching them (including phantomity ;) ).

10 October 2011, 11:08 PM
Sweet, thanks! Very handy.

While I'm on the subject of layers, how would I blur shadows using an area light other than increasing the size? I read something about a shadow shader, but how to create it was vague. Anyone know?

Robert Magee
11 November 2011, 02:54 PM
Here is a simple file that comps three simple (and ugly) objects using diffuse, reflect and shadow passes in Mantra. These passes are set up in the render output nodes and you will find one render output per object in the scene. The other objects are set up as mattes in the output node. By rendering all the passes in one go like this instead of using takes and different render outputs per layer, you save on render time and still retain control.

In the comp network you can see how the passes are pulled out of the .pic files using channel copy nodes then recomped using adds and multiply nodes. The shadow is interesting. You render out a shadow pass and diffuse with no-shadow pass then multiply them together. The result is then added to the scene. By altering the Foreground weight of the multiply, you can determine the strength of the shadow. A weight of 0 means the shadow is used completely.

Check out the file and if you have any questions about how it works then let me know.


11 November 2011, 09:25 PM
Thanks Robert, I will check that out.

12 December 2011, 08:57 PM
I have another question regarding masks. I want to know the most efficient way to mask a volume. I could do it by adding a pyro shader to the autodop sop for instance, but the render times are crazy.

I tried a constant shader and tweaked Volume Filter and Volume Filter Width in the sop parameters but the render looks choppy and not fluid like. The constant shader must be only for surface type objects.

Any thoughts?

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12 December 2011, 08:57 PM
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