https://bugs.freedesktop.org/show_bug.cgi?id=66067
--- Comment #9 from Nicholas Miell nmiell@gmail.com --- (In reply to comment #7)
Trine 2 uses those old assembly-like shaders for some reason
It's the minimum spec target profile for Nvidia's Cg compiler.
This cannot work as shadow sampling is only defined for depth textures. According to the ARB_fragment_program_shadow specification (Trine 2 uses those old assembly-like shaders for some reason), it is undefined behaviour to sample from non-depth textures.
ARB_fragment_program_shadow may leave it undefined, but the GL spec says the texture unit operates in the normal manner and texture comparison is bypassed if the currently bound texture's base internal format is not DEPTH_COMPONENT or DEPTH_STENCIL.