Refactoring Arx Fatalis

Subsystems - Discussion regarding the engine initialization and its major components

Scripting

• Remove / cleanup the script parsing in GetInfosCombineWithIO
• Parse scripts into some form of IR instead of executing directly.
• Share loaded scripts between IOs
• Match timers by name when loading savegames
• Cleanup GetInfosCombineWithIO()

Savegames

• Keep the SaveBlock instance open througout the game (and create it at game start to simplify things)
• Autosave when changing levels - almost all needed information is already saved here
• Track which IOs changed and don't always save all of them!

Audio

• Implement environmental effects (reverb) for the OpenAL backend using the EFX OpenAL extension. Reverb is available in the DirectSound backend when EAX is available (Creative drivers only?)

Interface

• Rewrite that mess.
• Fix aspect ratio of some interface elements for non-5:4 resolutions.

Renderer

Current state

• Lighting is done on the CPU
  • Static light components are pre-calculated for static scene meshes
  • Other lighting is done per frame

• Lighting is per vertex only - there is no support for per-fragment lighting effect (normal maps, ...)

• Vertex transformation is done on the CPU, except for static scene meshes
  • Animation is done on the CPU
  • OpenGL doesn't directly support the pre-transformed vertex format used, we currently use a small vertex shader for this
  • D3D doesn't clip the pre-transformed vertices - we removed (some of?) the SW frustrum clamping code and this has caused rendering artifacts for some users

• Vertices are already managed in vertex buffers, there is little of the immediate mode GL API

• We don't have any shader infrastructure
  • Possibly useful project: shiny

• Vertex colors are stored as the D3D-friendly BRGA format - OpenGL needs the ARB_vertex_array_bgra extension for this.

• We have no infrastructure for post-processing effects
  • This could remove the need for he normal rendering code to know about some spell effects
  • This could be useful to reimplement brightness/contrast/gamma, at least in windowed mode or when not otherwise supported.

Goals

• Hardware transform & lighting

• What OpenGL / Direct3D versions do we want to target?
  • Under Linux we should support the open-source Mesa drivers, but for what chipsets
  • For D3D we already use D3D9
  • For OpenGL we may currently technically be able to run with GL 1.5 but really need some extensions to run well
  • OpenGL ES support would be really useful
  • We could have multiple backends / code paths with different requirements

• Will we be using forward rendering (used now) or deferred shading
  • Transparent objects are in the minority (and often are emissive or don't have normal lighting) while there are many small lights, so deferred shading could be a good option
    • However, we probably need to deal with the lights anyway for the shadows and separate real light sources from those that are used to simulate global illumination

• We want to upgrade the visuals while also staying true to the original game atmosphere
  • Some effects that could be nice
    • Parallax bump mapping, Legend of Grimrock style :)
    • Improved fog
    • Nicer water
    • Have actual text rendered on in-game notices/signs (just so we have an excuse to implement distance field text rendering)

• Long-term goals to keep in mind:
  • Support for offscreen rendering and post-processing (with depth buffer available)
  • Supports for real shadows (shadow mapping or shadow volumes?)
  • Support for HDR rendering
  • Support for stereographic rendering
    • This means separating updating (physics, animations, ...) and rendering, which is a good idea anyway!

Also see the List of Milestones.

Roadmap

1. Separate game logic and rendering code
2. TODO