Multi displacement method can be very handy when setting up various displacement files for your geometry. It will enable you a higher detailed displacement for your render.

Maya
When preparing geometry for export to mudbox, it would be wise to layout the UVs on the positive direction of the U.
Note: when moving a UV shell, make sure it will move to the right spot.
Use this Mel Script: polyEditUV -u 1 -v 0 ;
Where the “1” is the value of the unit the shell is moving to

This is done to allow better naming convention for the displacement maps.
Mudbox will look at the lowest UV shell on the left side and generate the first displacement map.
For example: “xxx001.tiff”
I will then move to the second shell on the right and so on

Note: If you have placed UV shells on the V direction as well, Mudbox will go through the lowest UV lineup first, then move up and start again from the left.

Mudbox
When extracting the displacement (or normal maps) out of Mudbox, make sure the “Process Multiple Tiles” option is turned ON.
“URange” option means: where the distance of the first UV shell is located. Remember the tiles are in a UV 0-1.
Note: The parameter is named “URange,” hence the reason we have laid out the UVs on the U direction.

Once the operation is completed, you will end up with a number of displacement maps named according to the UV layout.
For example: sphereDisp0001.tif, sphereDisp0002.tif, sphereDisp0003.tif, sphereDisp0004.tif, sphereDisp0005.tif, sphereDisp0006.tif

Maya
Create “x” file nodes (where x is the number of displacement files.)
If you have done everything correctly, you should end up with displacement maps that reflect their associated UV shell.

In the “place2dTexture” Nodes, adjust the following;
Un-check “Wrap U” and “Wrap V”. This will prevent the texture from repeating itself in other tiles.

“Translate Frame” parameter will reflect where this texture node will be located on the UV layout.
File 1: Should be left as is.
File 2: Should be translated ONE unit on the U direction.
File 3: Should be translated TWO units on the U direction, and so on.

To combine all of these nodes into one, we will use a “PlusMinusAverage” node.
Connect the “out.Color” of each file to the “plusMinusAverage.input3D”

Note: The default color for the displacement files are set to gray.
Since we have disabled the texture wrap, the empty areas will be filled with this default color. This means unnecessary color information.
To fix this, change the “Default Color” to black for each file node.

While we are on the file node topic, flip the “Filter Type” to OFF.
The ultimate goal is to use Mental Ray. However, Mental Ray has a pre-built filter in the render settings.
This way we don’t have a double filter on our file texture.

Since the outcome value of the “plusMinusAverage” node is RGB, luminance is required for the displacement value.
We need to connect the “plusMinusAverage.output3D” to “luminance.value”.
Then, connect the “luminance.outValue” to the “displacementShader.displacment”.
Finally, connect the displacement node to the SG node of your shader.

Adjust the mental ray approximation node to your liking. Now the render will not show any seams in the UV border edges.

note: The same method can be applied to combine multiple color/normal/spec/bump maps.

You can use this mel script that will do everything for you

multi_disp.zip

Note:
Some might question the reason of using “out Color” rather than “out Alpha”It is true that we should use “out Alpha” but, due to few limitations with mental ray for Maya it was “easier” to use out color.Mudbox floating displacement work nicely with this method.However if you wish to use the “alpha gain/ alpha offset” trick. This above method won’t work.
We will need to redo our shading network and “convince” mental ray to respect these changes in the alphaHere is an example of such network

New Mel is provided

 

newmulti_disp.zip

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This entry was posted on Wednesday, June 25th, 2008 at 7:12 pm and is filed under Maya. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.