What's their difference?

[actarus1]

ng~~ pumpmapping...... ar, this make me remember a question, that is, in soft, what's the different between using pumpmapping and adjust the roughness of a surface in texture?
yes, this is my question~

[fredc]

I think you mean "Bump Mapping" verses Displacement Mapping.

You need Mental Ray to do Displacement Mapping, but Bump Mapping can be done with both the Soft renderer and MR.

I don't have time today to write a desent desciption, but here is essentially the difference.

Bump mapping is an illusion created by changing the direction of suface normals based on the light and dark areas of a texture. ie: Light areas appear higher and dark areas appear lower. This illusion has problems at the edges of sufaces becuse only pixel colors of the object are changed to make the illusion and therefore the edge of the surface appears not to be effected. Regardless bump mappins is still sufficient.

Displacement mapping uses the light and dark areas of a displacement map to actually deform the surface in 3D space. Therefore, there is no issue around the edges.

A couple of other issues to consider. Bump mapping is not dependent on the resolution of the surface or polymesh. However, displacement mapping requires that the geometry to have sufficient resolution to handle the details needed. Therefore, the second method is much more costly in rendering times.

Urp

[actarus1]

oh~ nonono~~~ no displacement mapping~ sorry for my description not clear enough~
I mean roughness - that is a variable inside the "texture" (or maybe material, i can't clearly remember~) there is a variable called roughness which can let you adjust (just like adjust the RGB color, the same kind adjust method), so can u get what i mean ;p

solution hong

[fredc]

Opps, I should have said more.

The roughness value controls both bump map height and displacement height. By height, I mean the amount that the surface appears to be lifted above or below normal.
If you leave the displacement unchecked you get bump, if you check it you get displacement. For displacement, rememeber you need to use MentalRay.
The value for bump roughness assumes that 1.0 is the max you would get for the lightest color or the darkest. Larger numbers are allowed and continue to keep making the bumps appear higher (or lower depending on light and dark values).
For displacement, the roughness value is in soft units. So 1 is 1 unit in the scene. The same value may be drastically different between bump and displacement.

Urp

[actarus1]

ic~
but why i haven't make use bump map texture for make my chair but i still can use roughness to adjust the roughness of my chair??

solution hong

[fredc]

You should be able to use any texture as a bump. Just apply your texture and move the roughness slider to atleast 1. To help you see the result, you can turn the blending value (on the texture dialog) down to 0. This will allow you to see the resluts of the bump.

My guess is that you have your texture mapped imporperlly. Be sure you can see your texture displayed like you want it to be on you surface with mapping method. You can use check swap UV to swap the UV of the texture on the surface. If you still need the texture to rotate, you can go into texture mode by selecting TXT at the bottom right of the screen. Now when you scale rotate or translate, you will be effect the texture, instead of the object or tagged points. Be sure to select OBJ when you are done to go back into object mode.

Hope this helps,
Urp