void SetTBN(int vertex1, int vertex2, int vertex3)
{
Mesh.ObjVertex v1 = objVertices[vertex1];
Mesh.ObjVertex v2 = objVertices[vertex2];
Mesh.ObjVertex v3 = objVertices[vertex3];
Vector2 dUV1 = v2.TexCoord - v1.TexCoord;
Vector2 dUV2 = v3.TexCoord - v1.TexCoord;
Vector3 dPos1 = v2.Vertex - v1.Vertex;
Vector3 dPos2 = v3.Vertex - v1.Vertex;
float r = 1 / (dUV1.X * dUV2.Y - dUV1.Y * dUV2.X);
Vector3 tangent = (dPos1 * dUV2.Y - dPos2 * dUV1.Y) * r;
Vector3 bitangent = (dPos2 * dUV1.X - dPos1 * dUV2.X) * r;
v1.Tangent = tangent;
v1.Bitangent = bitangent;
v2.Tangent = tangent;
v2.Bitangent = bitangent;
v3.Tangent = tangent;
v3.Bitangent = bitangent;
objVertices[vertex1] = v1;
objVertices[vertex2] = v2;
objVertices[vertex3] = v3;
}
int AddObjVertex(ref Vector3 vertex, ref Vector2 texCoord, ref Vector3 normal)
{
Mesh.ObjVertex newObjVertex = new Mesh.ObjVertex();
newObjVertex.Vertex = vertex;
newObjVertex.TexCoord = texCoord;
newObjVertex.Normal = normal;
objVertices.Add(newObjVertex);
return(objVertices.Count - 1);
}