displacement rendering in Blender and Max

Support Lighting and Rendering
1

Hey all.

I have been wondering about materials in Blender and 3DS Max lately.

I noticed that as I ramp up or assign an image based displacement in the material section in Max the resulting material will actually change the underlying geometry without affecting render time (okay, so maybe render time is not the question to ask since the engines and background are different, but bear with me).

Assigning any type of bump or normal map in Blender only makes cosmetic changes in the sense that the geometry remains the same At least to my knowledge looking at a sphere with a noisy normal map set to infinity will still have a smooth edge. Displacement modifier has the geometry-changing effect as described above, but the plane needs to be subdivided an appropriate amount for it to work correctly. It takes too many subdivisions to make the results perfect, but by then you (or myself alone) can’t render it (in our lifetime) because the polycount has gone off the charts.

I am not trying to make a contest of the two, I am just curious as to what causes these differences technically. Like I mentioned before I don’t understand how Max can change geometry without affecting render time - I imagine it would be possible to midify a lowpoly to subdivide and displace vertices based on a map’s intensity but that would, again, raise the polycount.

Weird.

2

A displacement map in Max will change render time. What happens is basically that the mesh is automatically subdivided during rendertime to a high enough degree and after that the displacement takes place.

In Blender you can do something similar but you have to set Cycles to “experimental” and in the object data pannel check “true” checkbox.
Here´s the relevant section in the manual. There is also a “subdivide” checkbox which does exactly what it sounds like:
https://www.blender.org/manual/render/cycles/materials/displacement.html

3

This is very interesting, I’ll have to play around with it. Thanks!

EDIT:
Tried it and for anyone reading this at some later point, I noticed some changes though not quite what I was expecting. “True” seemed to work just like bump, meaning that negative elevations were discernable upon prolonged inspection, but positive remained on the base polygon level. Furthermore, even with the negative parts the edge of the mesh was still visible, though in a darker, more transparent hue.