Shared Ownership of Rendering Resources

Among the most challenging design decisions in writing the rendering code has been the issue of ownership. In order to avoid linking the rendering logic too closely with the data, most of the rendering is done by separate Renderer objects (i.e., to render an AliasModel, one must first create an AliasRenderer).

The process of converting on-disk model data to renderable format is fairly complex. Brush models are stored in a format designed for the Quake software renderer (which Michael Abrash explained quite nicely), while alias models have texture oddities that make it difficult to render them from a vertex buffer. In addition, all textures are composed of 8-bit indices into gfx/palette.lmp and must be converted to RGB in order to upload them to the GPU. Richter interleaves the position and texture coordinate data before upload.

The real challenge is in determining where to store the objects for resource creation (e.g. gfx::Factory) and the resource handles (e.g. gfx::handle::ShaderResourceView). Some of these objects are model-specific -- a particular texture might belong to one model, and thus can be stored in that model's Renderer -- but others need to be more widely available.

The most obvious example of this is the vertex buffer used for rendering quads. This is conceptually straightforward, but there are several layers of a renderer that might need this functionality. The ConsoleRenderer needs it in order to render the console background, but also needs a GlyphRenderer to render console output -- and the GlyphRenderer needs to be able to render textured quads. The ConsoleRenderer could own the GlyphRenderer, but the HudRenderer also needs access to render ammo counts.

This leads to a rather complex network of Rcs, where many different objects own the basic building blocks that make up the rendering system. It isn't bad design per se, but it's a little difficult to follow, and I'm hoping that once I have the renderer fully completed I can refine the architecture to something more elegant.