|
|
Topic: Displacement Modifier: Taking geometry to another level
posted by MIKE_KENNEDY
archived on 10.5.2002
I was wondering what the settings in the VRAY Displacement Modifier were for. I love this new feature, already using it in production, but it would be great if I know what all the setting did.
Follow-ups
A: NOTE on displacement mapping:
If you want to add displacement mapping to an object, you must apply a VRayDisplacementMod modifier on that object. The object must have mapping coordinates in its first texture channel - it will not render otherwise. Here are the parameters of the modifier:
Texmap - the displacement map. At this point VRay works only with 2D textures ("Explicit map channel" mapping type only). If no map is specified, VRay will use a default simple fractal noise map.
Amount - the strength of the displacement map. Both positive and negative values are allowed.
Resolution - internally VRay only supports displacement maps in the form of bitmaps. Therefore the specified texture will be sampled with the given resolution. Increasing this will make the displacement more detailed, but will take more memory. Note that a displacement map must be compiled in a special structure to allow for faster raytracing; the size of this structure can be significant (it will probably be reduced in future versions). Avoid using large displacement maps if you can achieve the result with a smaller tiled map; use the fact that you can apply the same modifier to several objects.
Shift - offset value that will be added to the displacement map.
Use average - when this is checked, the Shift value will be ignored and VRay will use the negative of the average value of the displacement map as a shift.
Precision - controls the precision of the result when intersecting a ray with the displacement mapped object. The value of this parameter should depend on how "curved" the displacement mapping is; for landscapes you can set Precision to 1, which will make things faster. For more complex shapes Precision needs to be higher to avoid artifacts in shadowing and reflections/refractions.
Tight bounds - when checked, VRay will compute the bounding volume of the displaced triangles more precisely which may speed up the rendering.
VRay's displacement mapping is quite independent of MAX's displacement mapping mechanism and you can combine them freely.
Displacement mapping is still a very new feature to VRay, so bugs are quite probable. Also, rendering displacement-mapped objects is quite slow compared to normal geometry. Use displacement mapping only if there is no other way to achieve a given effect.
Analytic motion blur for displacement-mapped objects is not supported, you have to use Monte Carlo motion blur.
Q: Thanks for the info, I am only unclear about why I would use the SHIFT parameter.
A: Well, imagine that you have a map of bricks; the bricks are white and the gap between them - black. The displacement will push the white part (the bricks) out, and the gaps will be at the place of the original geometry; however you may want to have the bricks stay at the level of the original geometry and the gaps to to be pushed inside the object, and in this case you can use a Shift of -1.0.
> print this entry
|
 |
|
|
