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bertjenkins
10-12-2010, 06:50 PM
Hi

I have an issue with a 2 milllion poly head built in mudbox. Basically the level 5 version of the head is looking just right, there's a lot of detail, heavy wrinkles and creases, skin pores etc. I built the topology in maya and was quite happy with it for rigging purposes.

However when i bake a displacement map of the mesh the result is terrible. I am not allowed to use the level 0 (5000poly) mesh to generate the map using the subdivision method as it says the topology is different. How can it be different if i used it to build the high rez mesh in the first place? (I have since discovered there are two tris in the model. Could this be the reason?)

Instead i have been using the raycasting method and the displacement map is really rubbish. It has visible poly edges and spiky areas. I fiddle around with the mental ray aproximation editor and it improves slightly but is still totally un-usable. Even if I use 'Sculpt using displacement map' there are weird artifacts on the model in some of the cavities, etc. which to me suggests maybe a UV issue?

I thought i'd try and clean up the topology a bit using topogun, and when i test out the subdivision i get lots of spiking and artifacts. The map generated by topogun is a little better but seems to have a grid pattern on it from the low poly mesh.

Now i am at a loss to find out how i can get a good displacement. Does it seem like a UV thing? The mesh has various UV borders on it and in some areas the wrinkles are very severe.

Or is it because of the two tris on my base mesh - please say no!!!

Does anyone have any tried and tested workflows for getting a good displacement from a detailed head mesh? I've tried plenty of the tutorials but they seem geared toward mental ray approximation, rather than explaining the theory baout subdivisions, quads, uvs and displacement maps.....?

Any help would be soooooo helpful

bertjenkins
10-15-2010, 11:43 AM
Hi Guys

Thought id post a a result as i've found the solution. Seems that even two tris in a mesh prevent you from using the subdivision method for displacement maps (as opposed to raycasting) I'd been bashing my head against a wall over this. Also you can import a mesh onto the same layer as long as the uv's match.

In the end i fixed my Level0 mesh (removing the two tris that prevented me from using subdivision method), re-imported the old uv's, ending up with a clean level0 mesh with the same uv's. I subdivided the result 5 times, then imported the old (detailed) level 5 sculpt as a layer (i was able to import as the UVs were now identical, even though the vertex count is different). I then tweaked the overlapping areas, flattened the layers between the old and new, and was then able to bake using the subdivision method. The result is a million times better.



I think the subdivision method works better if there are lots of cavities, protrusions etc?

So far the base mesh seems to be deforming ok so i havent needed to use topogun yet. In a way that was just confusing the issue.

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10-15-2010, 11:43 AM
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