How do you extract bump map from sculpting?
My PC cannot take it when it gets too high polygon. I am a Mudbox user so some aspect maybe foreign to me.
You can make a displacement map or normal map in the Tool menu, but zBrush gives you very little control of the result, so I suggest you use xNormals which is a free program for doing this kind of stuff.
This tutorial might be usefull http://eat3d.com/zbrush-xnormal-pipeline
I think you can just use a displacement map bump, or just convert your normal map to a bump. (using xNormals “normal map to height” tool)
Ok thanks
But I realised that they dun have an option to convert a normal map to a bump…
or is it the Ambient occulsion or cavity map or heightmap?
Hmm, maybe it doesn’t have that option. But did you try making a displacement map and using that as your bump map? It’s really the same thing and xNormals lets you bake those out.
Also why can’t you just use the normal map? It’s far superior to a regular bump 
I would absolutely love to use a normal map but my clients engine doesn’t support it.