I just commented this on someone's blog post, thought I'd make it fair and share it with everyone. This relates to greyscale bump maps in an example on a brick wall texture & its bump map.
Bump maps work from difference between what's most dark and what's most bright. It often doesn't matter how high or low contrast your bump map is, but the bump node in maya is sensitive so you will always tend set it's bump depth value low. (Less is more in bump maps, Alan will say this.)
Think of it as a height map. Dark goes in, bright sticks out, so if your bump has cement seams in between the bricks as bright areas, Maya will make them stick out in the render when actually it should be the bricks that stick out. (inverting your map sometimes helps to get started -> CTRL + i in PS)
So the seams in between the bricks should be dark. They should be darker than any "noise" on the bricks themselves otherwise the noise will compete too much and obscure the effect of the seams.
The bump map should also be free of any "shadow information" that the texture could still have had. (Textures should almost never have apparent shadows anyway)
A good bump map takes some painting in photoshop.
Bump maps work from difference between what's most dark and what's most bright. It often doesn't matter how high or low contrast your bump map is, but the bump node in maya is sensitive so you will always tend set it's bump depth value low. (Less is more in bump maps, Alan will say this.)
Think of it as a height map. Dark goes in, bright sticks out, so if your bump has cement seams in between the bricks as bright areas, Maya will make them stick out in the render when actually it should be the bricks that stick out. (inverting your map sometimes helps to get started -> CTRL + i in PS)
So the seams in between the bricks should be dark. They should be darker than any "noise" on the bricks themselves otherwise the noise will compete too much and obscure the effect of the seams.
The bump map should also be free of any "shadow information" that the texture could still have had. (Textures should almost never have apparent shadows anyway)
A good bump map takes some painting in photoshop.
No comments here yet? Whaaaaa'
ReplyDeleteInformative post Pol, i'm sure someone will find it useful!
really helpful indeed, We are on our 1st steps of texturing and hints and tips are always welcome.
ReplyDeletethanks
woww. how does maya make it work? ive always been confused about how it figures it all out. does it just give the illusion of bumps? and why cant the colours in the textures do that on thier own? sorry about loads of questions, curious :D
ReplyDeleteThere's a lot of information on the net about how bump maps really work. The calculations behind the process are beyond what most of us really want to know though.
ReplyDeleteIllusion? Yes, it's all about illusions in CGI :P. But yes, bump maps do not deform your geometry. The same applies to normal maps, which are more of an advanced way of bumping textures since they allow more control over face's normals than plain greyscale bumpmaps. Then there's also parallax mapping which is popular in games these days. It gives an even more dramatic effect and bumps can even be made to appear to obscure each other. (Maya doesn't support this.) The only technique that really deforms geometry is displacement mapping. It's inefficient though because it's slow to render and slow to tweak.
The colours in the textures can be used as bumps. You could connect the color texture file node to the color channel & bump node as well, it will work. It will look at the brightness of the colors just like in a greyscale texture. The problem is that you won't be able to edit the map, and everyone will spot your laziness because the results will be poor.