Original Post
Hi people, When a normal map appear wrong on a model, who to blame? The artists or the code? Can anyone give me tricks to handle that? If you think it's art related, how should they be careful in 3ds max while modeling, and in which direction to setup their normal maps. If it is the code, can somebody tell me what I am doing wrong? Here is how I compute a tangent / bitangent : ( Assuming I am calculing verts[0] for the triangle verts[0..2] ) We will eventually rework the Max exporter to get the values 3ds max gives us, but for now I need the artists to visualize at least a correct model. Thanks a lot guys.
Edge1.Set(
verts[1].x - verts[0].x,
verts[1].y - verts[0].y,
verts[1].z - verts[0].z);
Edge2.Set(
verts[2].x - verts[0].x,
verts[2].y - verts[0].y,
verts[2].z - verts[0].z);
Edge1uv.Set(
verts[1].u - verts[0].u,
verts[1].v - verts[0].v);
Edge2uv.Set(
verts[2].u - verts[0].u,
verts[2].v - verts[0].v);
HGfloat cp = Edge1uv.Cross(Edge2uv);
if (cp != 0.0f)
{
HGfloat mul = 1.0f / cp;
tangent = (Edge1 * -Edge2uv.y + Edge2 * Edge1uv.y) * mul;
bitangent = (Edge1 * -Edge2uv.x + Edge2 * Edge1uv.x) * mul;
normal.Set(verts[0].nx, verts[0].ny, verts[0].nz);
bool inverted = false;
if (normal.Dot(tangent.Cross(bitangent)) < 0) inverted = true;
if (inverted)
{
tangent = normal.Cross(bitangent).Normalize();
bitangent = tangent.Cross(normal).Normalize();
}
else
{
tangent = bitangent.Cross(normal).Normalize();
bitangent = normal.Cross(tangent).Normalize();
}
}
verts[0].tx = tangent.x;
verts[0].ty = tangent.y;
verts[0].tz = tangent.z;
verts[0].bx = bitangent.x;
verts[0].by = bitangent.y;
verts[0].bz = bitangent.z;
