Max8/zbrush2 - Bad Normal Map Seams

[projectironwill]

We need to have separate normal maps for the different pieces of the body on a humanoid to increase detail levels, however we need to find a way around the seams.

Our current process of normal mapping includes the following steps in our workflow:
1. Model a lowpoly version of the object using 3ds max 8:
2. UV map the object in 3ds max 8
3. export the object as an .obj with texture coordinates
4. Import .obj into Zbrush 2
5. Subdivide and create high resolution model
6. In texture pallet create new texture of size 2048*2048
7. return to lowest level of detail and generate normal map using zmapper
8. Flip the texture vertically in order to orient correctly for 3ds max 8 and export
9. Export the new low poly object as .obj
10. Import to 3ds max 8 and apply normal map, render, end of story.

This process seems to work correctly if the object is comprised of only one mesh. If the object is, for example, a humanoid and the arms, torso, head, legs are separate meshes in order for each piece to have its own separate texture and normal map, there remains a visible seam between these meshes when the normal maps are applied.

This process includes:
1. Modeling the object in 3ds max 8 and making two copies of it, one copy a unified mesh, the other copy made up of the separate pieces in order to have separate uv maps. The unified mesh also has the same uv map shapes, except they are all in one map in order to copy/paste the normals to the separate object maps later.
2. The unified mesh is brought into Zbrush 2, refined and a normal map is generated.
3. The normal map is then chopped up into pieces and for each piece of the original low poly mesh, the respective uv maps are distributed. For example if a mesh is created of a cylinder connected to a box, the cylinder can be mapped separate from the box. A copy of the object can be made and the cylinder can be 'detached' from the box and retain its uv map coordinates. If the original object is detailed over the seams that connect the two components (cylinder and box) a normal map can be generated. If this normal map is split into two texture files, one containing the cylinder's map, and the other containing the box's map, the normal maps can now be applied to the separate objects created(cylinder and box).

The problem is that a terrible seam occurs where the two objects come together. Obviously if the two objects were never detached there would be no seam in the normal map.

Is there a better solution to creating separate normal maps for the different body parts without creating hard seams?

[andrew-raz]

if i understand you correctly, you are trying to apply normal maps to what are separate objects without the seams? if that's what you're trying to do, it simply won't work, because the smoothing algorithm smooths across contiguous connected surfaces; it can't smooth surfaces that aren't connected at their intersection.

the normal map works by telling the renderer what the surface normal vector is at each pixel coordinate of the texture (normal map) file. for tangent space (primarily blue) normal maps, that vector is relative to the surface normal. unfortunately, that means at each uv seam, the normals on either side of the seam are facing away from each other, producing a hard edge that can't be avoided. the only way around that is to use world-space or local space normal maps, which are usually more rainbow colored. these normal maps tell the renderer at uv coordinate X, the normal vector is XYZ, in an absolute sense, rather than relative to the surface. for that reason, it doesn't produce the seams, but the models can't animate, because as soon as the model deforms, the normal calculations are wrong. think of the normals on the top of a model's hand: when the hand twists 180 degrees, the normal map is still telling the lighting engine that the normals are facing up, even though they are facing down, which is incorrect, and produces black artifacts.

however, like i said, neither of these can fix seams over unconnected surfaces. the best bet is to either attach the object and uvs, or simply place the seams where there are hard edges anyways and hope people won't notice (and mos of the time they don't unless they're looking for it).

i hope that helps and that i didn't go too far off-topic or tell you something you already knew.

[joojaa]

but! you can use many uvsets taht overlap a abit and tehn do a blend between the 2 solutions!

[oliver-39-raz-39-]

Jooja yup its possible of course but it 'll be never as clean as a one part objet normal mapped i guess....painting normal with hand is not a very clean way to do and its hard to do !!!

[dellungo1]

Does max6 support normal maps?