Multiple Displacement Limits/Warnings Workflow

[Remydrh]

Ok, so I have a situation where I have multiple objects being displaced and a large amount generate a "max displace" warning.

Most of these values are easy enough to take care of with a global override, but there are a few that legitimately go beyond that limit so a global override won't help me without clipping.

And related: Fine and Max Displacement Thread

How is this best handled?

[steve]

For Maya,
the suggested approach would be to determine the displacement bounds inside your DCC before rendering, like using the Calculate Bounding Box Scale button in the Displacement Map rollout of the AE. That will be picked up by mental ray for Maya to compute the max displace setting. I agree, it is not very convenient doing it manually but it can be automated I think.

[Remydrh]

Thanks, I did that on a few nodes but wasn't sure if I remembered it being passed to mental ray correctly. I'll try that.

[Remydrh]

Using the calculate option causes it to produce clipping warnings instead of max displace warnings.

In either case it pre-samples the displacement, which I thought was supposed to help eliminate or reduce such errors anyway.

[steve]

Using the calculate option causes it to produce clipping warnings instead of max displace warnings.

I am only aware of these cases where it may not work:

• displacement is not connected through regular shadingEngine displacement slot, but mental ray's specific slot,
• the displacement shader graph contains custom nodes that do not work inside Maya,
• the shape to displace is a flat plane.

[Remydrh]

One object is a flat plane. But the other limitations don't technically apply. The objects do have a subdivision approximation set: parametric and fine.

For one object before calculate bounding box I get:

GEOM 0.35 info : performance warning: object HW_027_bridge_bg_Ref:polySurfaceShape444 [58]: displacement shader returned values up to 0.0735626, please check whether max displace 12.9716 could be reduced

After calculate I get:

GEOM 0.35 info : performance warning: object HW_027_bridge_bg_Ref:polySurfaceShape444 [58]: displacement shader returned values up to 0.0735626, please check whether max displace 9.48561 could be reduced

Other smaller shapes may give me the clip warning.

Oddly, the flat plane after processing the Calculate button renders without warnings.

Maya bug: Maya won't always use the calculate bounding box button because of an odd renderlayer bug that says "// Warning: Mesh shape waterFrontShape has no valid surface shader. Not tessellated." Despite having a shader and displacement correctly assigned. So have to be careful as usual with render layers.

[rarzer]

Hi there,

Excuse me for bringing back to life this thread. The truth is that I have exactly the same issue. I've been past two days looking for a solution without luck. Have you figured out how to solve this problem?

Thanks...

[Remydrh]

I think these warnings have sense been reduced in the output. I don't know if Maya has that fix yet.

I haven't tried calculate bounding box recently with SP2 (Haven't had reason to so far.) Have you tried that on your scene objects that generate warnings?

[mserena]

i just plug in the default lambert (via a script) run the calculate displace, which is just convert to displacement with bounding box on and disconnect after. It works for most displacements, but getting issues when plugging in any additional nodes.
http://core-cg.com/forum/messages.aspx?TopicID=64
getting displacement approximations in the area of ~75397676812064248100290560.000...even 'infinity' pretty cool !