Problem with bump maps - underlying topology creases it

[ioflowstudios]

Hi Everyone,

First time posting here, so hello

I have a problem when I paint bump maps in Sculptris, the underlying topology seems to be creating "creases" in my normal map... is there a way to solve this, or it a known issue that doesn't yet have a solution?

[justadeletedguy]

Yes, There is the possibilty of this problem, not really a fix but understanding it might help to avoid it some. What you must understand is that unlike "Baking" in Zbrush or Blender, your painted normal map does NOT "round out" the harsher corners of the low-poly model. This is my biggest complaint with Sculptris, that you cannot import a Bump/Normal map, as it says it can in the PDF.
Along with this, When painting in Sculptris, sometimes you'll find your alpha's get distorted going around corners. This is because it's mapped out your texture according to Camera angles, including the Vewport Camera.
All you can really do is experiment some to understand it better. Avoid putting much detail near UV-seams, and try and keep the View aligned directly parallel to the polygons you are painting.
I've been playing around with UDK lateley, and they've got a node-based way to combine Normal Maps. I believe something similar could be applied in Blender.

[justadeletedguy]

Yes... after playing around with it a bit, You CAN use "Overlay" in Paint.Net to build up normal maps. To make this useful you'll need to Bake your High-Poly onto your Low-Poly (I followed the tutorial Here ), then you paint to your normals in Sculptris, Then combine the two in Paint.net Using Overlay, and maybe turning saturation off in the Blue (color Mixer). It works, although I need some practice to get a decent example ....

[ioflowstudios]

Hi Justdeleteaguy,

Thanks for your advice, it's useful information. Having said that, it doesn't really answer my first and main question.

As you can see from my partially done normal map, I'm trying to paint hair for a low poly mesh but I'm getting nasty "creases" in my normal map where the underlying low poly geometry is. Perhaps I misunderstood the point of painting bump maps instead of sculpting, isn't part of it that you *don't* have to have a high poly mesh?

[justadeletedguy]

Re
Yes, But it's got it's drawbacks and flaws, and you just found one of them. It looks like a Quad-model, if so, then what I would do is import into Wings3d and Smooth (subdivide) the whole thing. It should keep your UV's in tact, and just round out the normals and smooth the surface. The export that as a separate object (bla_Highpoly.obj). Then Use the High-poly in Sculptris to paint on. Then export the Textures and use them on the original Low-poly model.

On that note, I'll show you a few more tricks. You can't paint external-symmetry UV-mapped models, but, you CAN paint Half a model (this can save a lot of texture space for more detail). Also, If you assign materials in Wings3d, then export, then do a quick import/export from Blender 2.6x, Blender will split the Materials into seperate objects. In Sculptris, the seperate objects can be hidden for easy masking and painting. This works well where materials change, (sleeve ends, hair line, etc).
As long as the UV's don't change, You can make whatever adjustments you need, moving, posing, smooth, in Wings3d or Blender, then export the result to paint on in Sculptris, and the Texure will fit the original model. As long as the UV's don't change

[ioflowstudios]

Ok cool, I can do this...

Thanks for your help