Claudia Herbst-Tait
Associate Professor
Pratt Institute
Department of Digital Arts

Adjusting Displacements Maps & Using the Height Field Utility

In Maya, create polyPlane, scale it and make sure it has a few subdivisions. It should roughly look like
what you see in figure 1.

Figure 1 (Beautiful!) 

Now,in the Hypershade, call up a File node as depicted in figure 2.


Figure 2

Assign an image to the File node. You can use/download figure 3, or use your own.




Figure 3

Connect the image to the File node as depicted in figure 4.


Figure 4

Call up a material--any will do (I am using Blinn). Middle-mouse button click and drag the image File
node onto the material node, from the pop-up, select "displacement map" (figure 5).

Figure 5






Assign the material to your polyPlane and do a quick test render. It'll probably look something
like figure 6: Eeks!

Figure 6

Next, select the polyPlane, open the Attribute Editor, and then expand the Displacement Map tab; adjust the Sample Rate
values to reflect what you see in figure 7. Do a test render. You should get the results depicted in figure 8.

Figure 7 (Btw, if your displacement map show black holes, click the "Calculate Bounding Box Scale" button
and test render again.)

Figure 8 You can further up the values and test render. Notice that rendering slows down pretty quickly...





Now, to make further adjustments, and to be able to see what those will (roughly) look like without having
to render, lets call up a Height Field utility node (figure 9)


Figure 9

With the Height Field node selected, scale the object that has been created in your scene to roughly the size of your polyPlane.

Next, click on the bottom right arrow of the image file node and select the outAlpha--you get a "rubber band."
Now, left-mouse-button click on the Height Field node and (don't let go) select "displacement" from the pop-up (Figure 10).


Figure 10

Figure 11 depicts what you should now see in your scene file (you might have to scale the object.
Also, make sure your object is at 0, 0, 0).

Figure 11

With the Height Field still selected, open the Attribute Editor and adjust the values as
depicted in figure 12. Your scene should now reflect what you see in figure 13.

Figure 12

Figure 13 Also, try turning on shaded mode. The Height Field represents what your
desplacement will look like but it will not render.





Lastly, for the tweaking part, select the image File node, open the Attribute Editor,
and then the Color Balance tab. Adjust the Alpha Gain value (figure 14) and
watch what happens in your scene. The changes that you notice in the Height
Field relfect the changes in the discplacement map.

Figure 14

Thus, the Height Field node is helpful when tweaking displacement maps (without
having t rerender every step of the way). Next, try and check the Pre Filter option
(see figure 14) and do a test render. Also, note that the filter value can be adjusted
which softens the displacement map (i.e., adjust the "Pre Filter Radius").

That's it!