Getting normal matrix from modelview matrix

gl_NormalMatrix in your vertex shader ;)

http://www.lighthouse3d.com/opengl/glsl/index.php?normalmatrix

When I want to get the normalmatrix, I prepare a normalmatrix variable as Matrix4 and substitute "Inverse of modelview matrix" for it by using Matrix4.Invert .
Next, use GL.UniformMatrix4 for loading the variables into shaders .
Then, in a shader using normalmatrix(type is mat4), write "mat3(normalmatrix)" . It means taking upper-left 3x3 of the normalmatrix .

You can get the inversion matrix by using inverse(mat 4) as well.

Sorry . I have forgotten to write about transposing matrix .
You can transpose a matrix by specifying an argument in UniformMatrix4 or writing "transpose(mat 4)" .