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1731

1722 Chapter 16: Material Editor, Materials, and Maps

encounter multiple return values in shaders provided

with other shader libraries or custom shader code.

Height M ap Displa cement S hader

(menta l r ay )

Material Ed itor > mental ray Conne ction rollout > For

the Displacement co mponent, turn off the lock button.

> Click the button for the Displacement component.

> Material/Map Browser > Height Map Displace ment

(3dsmax)

Material Editor > mental ray material > Cli ck the bu tton

for the Displace m e nt comp one n t. > M aterial/Map

Browser > H e ight M ap Displacement (3dsmax)

Note: Shaders don’t appear unless the mental ray

renderer is the currently active renderer.

The Height Map Displacement shader displaces

the geometry of surfaces, and is specifically

intended for use with height maps generated by

normal mapping; see Crea ting and Using Normal

Bump Maps (page 3–150).

Impor tant: When applying a material containing

this map to an object, the mental ray Displacement >

Smoothing option must be off. If such materials are

applied to all objects in the scene, you can turn off

Smoothing globally. Otherwise, turn off smoothing for

each object whose mater ial uses a height ma p via the

Object Properties > mental ray panel (page 1–126) (turn

off Use Global Settings and then turn off Smoothing).

Tip:

Avoid the temptation to apply MeshSmooth

to a model when creating a height map for it.

This changes the shape of the model so the height

values will not be correct. The low-res model

must have exac tly t he same shape when the map is

created and when it is used for displacement. Also,

MeshSmooth does not use the same a lgorithm as

the mental ray displacement smoothing, so using

both forms of smoothing won’t work perfectly.

The best results are obtained by not smoothing the

low-res model when the m ap is created and also

not using mental ray smoothing.

Also, avoid using a paint program to mo dify the

height map. The values in the height map depend

on the shape of both the low-res and high-res

models, and it’s easy to damage the mathematical

accuracy. If you paint any changes onto the map,

you must be careful to preser ve the faceted look,

and avoid the temptation to blur away the facets.

You might try painting in Additive and

Subtractive mode to add or subtract to the

displacement, because Normal mode will set a

fixed displacement, making it difficult for an artist

to control the result.