2008

Breaking low-res vertices causes the indentations to render in the normal bump map.
However, projection now misses some areas of the geometry, so the cage needs to be
adjusted further.
Flipped Seams in Tangent Space
When you use tangent space for your normal bump map, usually the values
used for the tangents are consistent between the hardware shader, renderers,
and third-party applications. However, sometimes portions of the geometry
are flipped, relative to each other, causing discontinuities when you render
or use a hardware shader. Tangent space is the default option for normal bump
mapping, and it is the method you should use for objects that both move and
deform, such as animated characters. This problem does not arise when you
use the other coordinate spaces: world, screen, or local.
For example, in the following scene, the pants show discontinuities. They are
flipped relative to each other, as the arrows show.
Troubleshooting Normal Bump Maps | 6189