Displacement maps

[Dade]

As discussed in Mantis feature #166, I wrote a first support for displacement maps. At the moment is a simple per-vertex displacement support and it uses LoopSubdiv shape support in order to tessellate the original triangle mesh.

You can use ay float texture as displacement map, for instance:

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Texture "displace_map" "float" "fbm" "integer octaves" [8] "float roughness" [0.500000] "vector scale" [0.100000 0.100000 0.100000] "vector rotate" [0 0 0] "vector translate" [0 0 0]

AttributeBegin
   Transform [1.0 0.0 0.0 0.0  0.0 1.0 0.0 0.0  0.0 0.0 1.0 0.0  0.74215400219 -0.382443904877 0.0311622619629 1.0]
   NamedMaterial "mat_sphere"
   Shape "loopsubdiv"
         "integer nlevels" [6]
         "string displacementmap" ["displace_map"]
         "float dmscale" [0.25]
         "integer indices" [
0 1 2
[...]


where:
- nlevels is the number of time each triangle must be subdivided;
- displacementmap is the name of a float texture;
- dmscale is a scale factor for the displacement map;
- indices, P are the same parameter of a trianglemesh (it is trivial to transform a trianglemesh in a loopsubdiv: just add the "nlevel" parameter).

Now some demo of this feature. The first image is an FBM texture applied as color (left) and applied as displacement map (right):

And the same for the Dots texture:

Indeed, I couldn't resist

Loopsubdiv shade doesn't support UV coords and it is the next thing I'm going to add.

As usual, it is the first implementation, your mileage can vary.

[dougal2]

bloody hell that was quick. I guess I'd better start on the loopsubdiv export module for LuxMaya.

[Dade]

A wrinkled Luxball:

A wooded Luxball:

[dougal2]

one small thing about the syntax. Shouldn't

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"string displacementmap" ["displace_map"]


be

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"texture displacementmap" ["displace_map"]


[Radiance]

what the hell is in the water in italy ?

that's great work dade, very fast

i'll have to conjure up some support in luxblend for this now

greetz,
Radiance

[Radiance]

oki,

Dade, i've noticed that the direction is wrong.
eg >1.0 becomes a hole (inwards of the model) and <1.0 (negative) becomes a bump (extruded outwards)
i think this should be inversed so it matches with the behaviour of bumpmaps.

it's useable without support for normals, but not on a propper scene, too much weird behaviour

support in luxblend is nearly done, just some more testing and cleanups.

you can make some pretty awesome stuff with this and our procedurals

greetz,
radiance

[Dade]

Dade, i've noticed that the direction is wrong.
eg >1.0 becomes a hole (inwards of the model) and <1.0 (negative) becomes a bump (extruded outwards)
i think this should be inversed so it matches with the behaviour of bumpmaps.

Wired, the code is

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Vector displacement(nn);
displacement *= displacementMap.get()->Evaluate(dg) * displacementMapScale;

verts[i] += displacement;


So the displacement should be along the direction of the normal (>0.0 => bump, <0.0 => hole).

it's useable without support for normals, but not on a propper scene, too much weird behaviour

Some strange behaviour could be related to the wrong values of some field I'm using in the DiferentialGeometry at the moment. I should fix that stuff today.

you can make some pretty awesome stuff with this and our procedurals

Eheh, I love the last Suzanne

[Dade]

one small thing about the syntax. Shouldn't

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"string displacementmap" ["displace_map"]


be

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"texture displacementmap" ["displace_map"]


You are right Dougal but I had to use "string" and not "texture" because the way the Lux parser is written. The "displacementmap" parameter is inside a Shape object and not in the definition of a Material. Shape object constructor uses ParamSet instead of TextureParams (only available for a Material).

[Dade]

I added the support for UV coords in loopsubdiv objects, now we can use imagemap too:

Wait for Radiance for a nice artistic demonstration of this feature

[Dade]

Added a "float dmoffset" option. It adds a constant to the displacement (i.e. using a -0.5 value for an imagemap between [0,1] can be useful).