How to determine the maximum supported level of anisotropic filtering for a graphics card

Question

In software, at runtime, (C++ if it matters), is there a way to find out the maximum level of anisotropic filtering supported by the graphics card?

Answer 1

In general you ask your graphics API you're using.

For example if you're using D3D9 you call IDirect3DDevice9::GetDeviceCaps() and then check the MaxAnisotropy value in the D3DCAPS9 structure.

On almost any reasonably modern graphics card the answer will be 16.

Answer 2

In OpenGL, you would (after creating a context and everything) do this:

GLfloat maxAniso = 0.0f;
glGetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &maxAniso);

Of course, this only works when the GL_EXT_texture_filter_anisotropic extension is available, but since every graphics card has supported this is about the year 2000, I wouldn't worry about it.