Thanks again markus.
I put up a issue about this on github.
just take the Monogame CreateLookat code and negate the right vector.
Not sure this is right but it appears to be.
public Matrix CreateLookAtLeftHanded( Vector3 cameraPosition, Vector3 cameraTarget, Vector3 cameraUpVector)
{
var vector = Vector3.Normalize(cameraPosition - cameraTarget);
var vector2 = -Vector3.Normalize(Vector3.Cross(cameraUpVector, vector));
var vector3 = Vector3.Cross(-vector, vector2);
Matrix result = Matrix.Identity;
result.M11 = vector2.X;
result.M12 = vector3.X;
result.M13 = vector.X;
result.M14 = 0f;
result.M21 = vector2.Y;
result.M22 = vector3.Y;
result.M23 = vector.Y;
result.M24 = 0f;
result.M31 = vector2.Z;
result.M32 = vector3.Z;
result.M33 = vector.Z;
result.M34 = 0f;
result.M41 = -Vector3.Dot(vector2, cameraPosition);
result.M42 = -Vector3.Dot(vector3, cameraPosition);
result.M43 = -Vector3.Dot(vector, cameraPosition);
result.M44 = 1f;
return result;
}
Here is a Desktop GL demo version that demonstrates the results of the post for reference.
I also found a inconsistancy on Dx.
Within the shader this struct will run on GL uncommented but not on DX.
struct VsInLightShadow
{
float4 Position : POSITION0;
// float3 Normal : NORMAL0; // uncommented this will run on gl but not on dx.
float2 TexureCoordinateA : TEXCOORD0;
};