Saving or creating an environment or reflection cube map

Question

Im just starting to use the reflection maps that are generated by the 'Indirect lighting' tab of the Eevee render settings.

I know these are saved to a cache and then sort of applied to the object, but i wanted to know:

• are these maps available to export (as an image file)?
• is there any way to see (or recreate) the shader-like settup that happens behind the scenes to apply these maps to the object?

I imagine recreating this effect would involve a shader that takes the view position into account, so would be cool to see how this is created. Also I would like to know if there is a workflow for baking these reflection maps in Blender and reusing in other applications/frameworks (like Babylon JS)

Answer 1

They're not available as export. You can set up a way to make them manually, but it's a bit of work.

You can see exactly how they work by reading code. Either Blender's code (which I haven't read), or by getting an idea from reading other shader code, which is probably very similar to Blender's implementation.

A reflection cube map is created by rendering the scene six times, from six cameras at the center of the cube but at right angles to each other, each with a 90 degree field of view, which corresponds to the faces of a cube. I believe that a reflection plane is created similarly, but from a single, orthographic camera.

Usually, reflection cube maps or planes are accessed by the reflection vector-- the reflection of the view vector over the surface normal, such that the surface normal bisects the angle created by the view vector and the reflection vector. We can then run this reflection vector through the perspective matrices for our cubemap or plane and get "screen-space" coordinates for a look-up on those renders.