Deferred(ish) Rendering

During the past few weeks I’ve been reviewing a lot of the rendering pipeline. One of the things I started working on is the new Deferred Render pass.

In short, Deferred Rendering (DR) is performed by first rendering the visible scene into a deep frame buffer (usually known as the G-Buffer), storing specific sets of data like positions, normals, colors, material properties, etc. Lighting calculations are then performed in a separate pass, computing the lighting equation only for the visible pixels. Here’s a great introduction to Deferred Rendering in general.

The main benefit of DR is that it makes possible the use of a high number of light sources, since there is no need to compute lighting for those pixels that are actually occluded by others. But I personally like it because it provides much more data to work with when applying screen effects like SSAO or Glow.

Since this is my first approach to Deferred Rendering, I didn’t want to complicate too much the layout of the G-Buffer:

G-Buffer LayoutA lot of space is wasted, I know. But then again, this is the first approach.

The following video shows the updated Lightcycle demo using deferred rendering and a glow effect. The video also shows the output for each buffer separately, for debug purposes

I also gave it a try to SSAO, which can be seen in the next couple of images, but I’m not comfortable with the results



Without SSAO

Without SSAO

As much as I like DR, making it the default render pass seems difficult in the near future. It requires a lot of memory and it’s dependent on the host platform to support multiple render targets (MRT), which is not standard. For example, GLES 3 does support MRT, but most mobile devices still have GLES2-based graphic cards.

Next steps are to compute lighting using light shapes and add some more screen effects. Stay tuned.


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