I have been trying to use an existing library that automatically generates shaders (Hydrax plugin for Ogre3D). These shaders are used to render water and somewhat involved, but are not extremely complicated. However there seems to be some differences in how the cg shaders are handled by OpenGL and DirectX, more specifically, I am pretty sure that the author of the library only has debugged all the shaders for DirectX, and they work flawlessly there, but not so in OpenGL. There are no compiler errors, but the result just doesn't look the same. (And I have to run the library in OpenGL.) Isn't cg supposed to be a language that can freely use the exact same code for both platforms? Are there any specific known caveats one should know about when using the same code for them? Are there any fast ways to find what parts of the code work differently?

(I am pretty sure that the shaders are the problem. Otherwise Ogre3D has great support for both problems, and everything is abstracted away nicely. Other shaders work in OpenGL, etc...)