How does one normally detect if a texture contains an alpha less than 1?

Currently, I am conservative and just check the DXGI_FORMAT. But if I want to use BC formats for all my textures, than all textures will be categorized as transparent?

I use this distinction to group my models into opaque and transparent models.

I require the material (referencing the textures and used by the model instance) to specify if it is rendered during the opaque or transparent pass.

5 minutes ago, GuyWithBeard said:

I require the material (referencing the textures and used by the model instance) to specify if it is rendered during the opaque or transparent pass.

Thanks, that is probably the most robust.