Frustration Displacement Spikes in Mental Ray

#1

I have a spike displacement problem with Mental Ray. The displacement map came from Mudbox, everything was flawless in Mud.

When rendering with Mental Ray, there are spikes in, what appears to be random spots all over the mesh. The only solution after pressing this question to numerous people is to paint out the thin lines that you see in the enhanced image of the displacement map. This works to an extent, but since there are so many thin lines, it’s hard to eliminate them all and completely remove the spikes. I’m at a loss on how to solve this, my UV’s are clean, as in there are no overlapping etc. I don’t mind a little clean up, as most would accept, but major clean up which there is no guarantee that I will not see spikes seems like an endless circle.

#2

may i see the uvs… the low and the highress…
mybe we could fix the baking issue…

#3

Here is an image of the UV’s.

#4

how does the mesh look like if you displace it in mudbox… is it possible that the dispmap is to small to carry the data.?

#5

After adding six levels and sculpting using displacement; the results prevail equivalent to the results seen in Maya ?

#6

are you baking with subD or raycast method…?

its possible that the uv space is to small so that its baking all into one pixel…
try to upress the texture or use UDIMs…

is the highres mesh a closed surface…?

#7

I baked with raycast. I’ll already baked out a 4K map, I’ll push for 8K. I can’t use UDIM because it is a single closed surface mesh; unless you mean to split up the UV in two parts ?

#8

Update:

The mesh already has UDIM; I baked out an 8K 32-bit EXR, then using sculpt with displacement in Mud to test the results, the spike continued. I did forget one more thing, to bake out, not using raycast but subdivision.

Exporting to Subdivisions showed better results, with sculpt using displacement in Mud. Although I wasn’t able to test the results of sculpt using displacement on the second UDIM tile as sculpt with displacement won’t recognize the second UDIM tile.

Masking one UDIM tile out doesn’t cause sculpt with displacement to work on the second UDIM tile to which I want.

#9

mud should read in the second tile by itself…
if you bake the tiles you should get them named like this…

name_u1_v1.exr
name_u2_v1.exr

#10

The second tile was read, there is an improvement on the first tile, the second tile the spikes continue, arghh.

Update: With sculpt using displacement I was able to get near the results I wanted, except for this seam in the mesh ?

#11

More or less solved. :slight_smile: