Deferred improvements

Revisit the deferred rendering implementation took me a little more time than expected and it wasn’t easy, but I’m very excited with the results and the flexibility that has been achieved.

In contrast with my last post, this one is gonna be all about visual improvements. So, let’s begin.

Truth be told, my original goal was to enhance just the post-processing pipeline, adding support for more than one image effect at the same time and then accumulating results. But I ended up refactoring the entire deferred render pass and added a couple of new things on the way. Because, you know, refactors are fun 🙂

As before, the Deferred render path is split into three stages: G-Buffer generation, lighting and post-processing.

The G-Buffer

The G-Buffer is composed of five render targets organized as follows:

G-Buffer organization

G-Buffer organization. Floating-point buffers are used whenever possible in order to keep data precision.

Both world and view space normals are stored for different purposes. As a matter of fact, view space normals are generated just from the geometry itself, without any bump mapping applied to them since some post-processing effects achieve better results with less information (i.e. SSAO)

g_buffer

The G-Buffer in action. Top row: depth, diffuse and world space positions. Bottom row: emissive (unused in this demo), world space normals and view space normals

Lighting

The second step is to compute lighting and generate a colored frame. Usually, this step involves two passes: one for lighting and one for the final composition, but I’m doing both in a single pass. There’s room for some improvements here, but I leave that to my future self.

Lighting computation, before applying post-processing effects

Lighting computation, before applying post-processing effects

Lighting is computed from world space information. Shadow maps are applied here after the scene is lit.

Post-Processing

Once the scene is generated, image effects are applied. A couple of auxiliary buffers are used (following the “ping-pong buffer” technique), accumulating results.

Ping-pong buffer. For each image effect, the source and destination buffers are swapped. Once all effects have been processed, the source buffer contains the final image

Ping-pong buffer technique. For each image effect, the source and accumulation buffers are swapped. Once all effects have been processed, the source buffer contains the final image

Concerning image effects, the new additions are Depth of Field and SSAO. There was a previous implementation for SSAO, but the new one performs blurring in order to reduce noise and improve the final results.

Applying Depth of Field to the scene

Applying Depth of Field to the scene

SSAO only

Rendering the scene with only the output from the SSAO effect, before applying it to the scene

Final Comments

In order to debug the entire process, I made it possible to render the results of all the passes at the same time. It is a costly operation, but extremely useful when trying to understand what’s going on. In fact, I’m planning to add this feature to other systems as well in a future iteration.

Top row: depth, diffuse, positions, shadow map (packed). Middle row: emissive (unused), world space normals (with bump), view space normals and screen objects. Bottom row: lighting and post-processing

Top row: depth, diffuse, positions, shadow map (packed). Middle row: emissive (unused), world space normals (with bump mapping applied), view space normals and screen objects. Bottom row: lighting and post-processing (SSAO + DoF)

That’s it for now. I’m done with refac–

Wait…

Those shadows look awful…