IdTech4 Open Source

id Software has a long history making the code to their engines open source after a while. Even after being sold to Zenimax, this trend continued. The source code can be found on the officiel FTP server from id software.

So there is hope that idTech4 (the engine behind Doom 3 and Quake 4) will also be open sourced. For The Dark Mod this means that we can fix a long list of issues that are currently not possible.

Here is a small, incomplete list, in no particular order:

Todo: add more examples

Category	Issue	Possible outcome
Sound	EAX does not work under Linux.	Works there, too.
Graphic	The lightgem needs to render to a texture and transfer this texture back to the CPU via a complicated in-memory file scheme.	Performance increase.
Graphic	No instancing. Multiple instances of the same model are all rendered one by one, instead of uploading it once and then telling the graphic card to render them all in one go.	Performance increase.
Graphic	No access to the Z-Buffer. Without access to this data, any depth-based fragment shader effects like SSAO or Depth of Field require an extremely expensive z-pass render.	Performance increase. More effect options.
Coding	Single-threaded coding. It may be possible to divide the sub-systems into separate execution threads for processing on separate cores once the source code is available. The game Prey has implemented this type of change to Id Tech 4. On the extreme side of concept, OpenCL could be used to perform AI path-finding, or physics calculations.	Performance increase.
Graphic	Shadow Volumes are calculated on the CPU. Moving to a GPU calculated Shadow Volume or a Shadow Mapping technique like Parallel Split Variance Shadow Maps would allow more on-screen geometry with active lighting applied. Soft shadows would also be MUCH less expensive than the current Z-Buffer render and Post-Process method.	Performance increase. Higher poly-counts. More active lights. Soft shadows.
Graphic	No access to Vertex positions. For vertex shader or geometry shader (DX10+ hardware) operations like R2VB, Vertex Texturing or Tessellation the correct Vertex locations will be needed.	Performance increase. Higher poly-counts.
Mapping	Brushes cannot have Vertex Colors or Vertex Normals. Adding these attributes would give Brushes near feature parity with Models and allow for more seamless mixtures of the two construction methods. Brushes could have Patch style smoothing and curves yet could be properly scissored by a Visportal. Translucency could be applied to Brush-work prefabs.	Performance. Ease of use for mappers.
Graphic	Support for Light-Maps or Deluxe-Maps. While static lighting methods are not really an ideal usage for this engine, these features can have their utility. You could bake ambient bounced lights for areas that are predominantly statically lit. To make these methods more Doom 3 compatible, these could be implemented as an Ambient Light (3D texture support?) as a more robust extension of the Strombine method that is currently available (but very cumbersome). Maps made in other engines (without game specific assets) could be more easily migrated?	Performance increase. Graphic enhancement. Migrated content?

See also

• FTP Server from id software

• Doom3world Wish List for Open Source Doom 3