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1541

1532 Chapter 16: Material Editor, Materials, and Maps

encounter multiple return values in shaders provided

with other shader libraries or custom shader code.

Height Map Displacement

Shader (mental ray)

Material Editor > mental ray Connec tion rollout > For

the Displacement component, turn off the lock button.

> Click the button for the Displacement component.

> Material/Map Browser > Height Map Displaceme nt

(3dsmax)

Material Editor > mental ray material > Click the button

for the D isplace m e nt compone n t. > Material/Map

Browser > Height Map 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

Creating an d Using Normal

Bump Maps (p age 3–146)

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

. Otherw ise, turn off smoothing for

each object whose material uses a height map via the

Object Properties >

mental ray panel ( pag e 1–121)

(turn

off Use Global Settings and then turn off Smoothing).

Tip:

Avoid the temptation to apply M eshSmooth

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 exactly the same shape when the map is

created and when it is used for displacement. Also,

MeshSmooth does not use the same algorithm as

the mental ray displacement smoothing, so using

both forms of smoothing won’t work perfectly.

The best results are obt ained by not smoothing the

low-res model when the map is created and also

not using mental ray smoothing.

Also, avoid using a paint program to modify 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 preserve 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 ar tist

to control the result.