Material_ID_texture sampler2D for post-processing

[goosegarden]

Adding a Material_ID sampler2D texture for post-processing.
It would display objects as flat-coloured with a different color for each material_id, so the color can be used to identify a specific mesh surface in the post-processing stage.
In addition to depth_texture, normal_texture and velocity_texture, it would give more possibilities for custom layered post-processing, by allowing to apply a specific post-processing effect to a specific mesh, or a specific surface.

[Calinou]

As far as I know, this can't be done efficiently in a forward renderer, only in a deferred renderer. If this is the case, then this proposal would depend on #8295 being implemented first.

[goosegarden]

What i suggest doesn't seem to be related to the proposal you mention. Even though G-Buffers are often used for deferred rendering, the point of this ObjectID buffer is not deferred rendering, it would be used for post-processing effects, more specifically targeted at non-photorealistic rendering.The same way, for example, the depth_texture sampler2D that can be accessed with hint_depth_texture, or normal_texture sampler2D that can be accessed with hint_normal_roughness_texture, can be used in post-processing (like, for a sobel filter) . I dont know where in the engine these textures are created, what i suggest is adding another one, to allow to identify a specific object in the post-process stage, so that some custom post process effects can be applied on specific objects rather than on the whole scene.