Maya and displacement mapping

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CTZn
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Maya and displacement mapping

Post by CTZn » Tue Jun 03, 2008 1:36 pm

What I can say on displacement within Maya (not supported in MtI as of yet):

You can use the displacement feature out of the rendering process, right into the scene. This is done through the menu item:
Modify > Convert > Displacement To Polygons.

You will notice that there are no options available for this command; that's because every polygonal shape beholds these options natively. Do the following to find them:
  • - Select the mesh in order to display it's properties in the Attribute Editor
    - in the shape's tab open the Displacement Map rolling frame. That was easy, now go use the doc :P
Okay now nothing will happen if you don't connect a displacement shader to the shading group (the shading group connects to the shape, the shader and the displacement shader alltogether). Let's create some:
  • - Open Hypeshade window

    - if the mesh is selected click onto the icon representing two green squares connected to a crossed blue disc.

    This will graph the shader assigned to the selected shape(s).

    - else what select the shader and click the box with two arrows to graph it's inputs and outputs.

    The shading group belongs to the laters.

    - on the left side of Hypershade is the Create Node pane; one single node lies under the Displacement rolling frame

    - hold [Ctrl] and drag the icon onto the shading group.

    Pressing the key told Maya to use a default connection, wich is not always what you want. Try the same with [Shift] and see what inputs and outputs these nodes have.

    - alternatively you could have connected the displacement shader by dropping (keys off) it onto the shader and selecting displacement map in the list.

    Nonetheless the new node connects to the shading group.
Now we've created and connected a displacement shader, what to connect ?

It takes a scalar value as input, that is: no color but a single channel. Generally that's the outAlpha from a texture node, so let's have a closer look at this.

Create any texture node from the Create Node pane and display AE (Attribute Editor); under the Color Balance frame you have amongst other attributes Alpha Gain and Alpha Offset. When plugged into a displacement shader, these values are read as Maya scene units !!!

Displacement will effectively occur within the range specified by the Alpha Gain value, from the cage surface if Alpha Offset is set to zero. Some examples:

Code: Select all

Alpha Gain = 1, Alpha Offset = 0
The furthest feature (white pixel) will be 1 unit away the original surface. No geometry will be created under the original surface.

Code: Select all

Alpha Gain = 1, Alpha Offset = -0.5
The features amplitude will be 1 unit as well, but the lower parts will lie beneath the original surface while the upper parts will be above. That's about it.

One way to check that the displacement is well balanced around the original mesh is to tweak Alpha Offset while having an eye on the displacement shader's AE: when the value is 0 it's fine. To do this select the displacement shader and in AE click Copy Tab, then select the texture and tweak.

Also it is handy to plug a multiply/divide node between the texture and the displacement shader. More on this later !

You can ask your questions yet, thought, if any.
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User avatar
CTZn
Posts: 7240
Joined: Thu Nov 16, 2006 4:34 pm
Location: Paris, France

Post by CTZn » Wed Jun 04, 2008 11:42 am

I did a mute video tutorial on rock creation and texture export.

It does not cover the igs hand editing part; the tags are exposed in Indigo 1.1.1 release pages.

rock_tutorial.avi.

I prefer answer any queqtion you have rather than explaining every detail. Enjoy.
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