feat: Terrain conforming particles

[stephanmeesters]

Merge by rebase

• Relates to Radiation & Toxin Fields Render Incorrectly on Uneven Terrain #1913
• Required by bugfix: Contamination fields render incorrectly on uneven terrain GeneralsGamePatch2#177

Summary

Makes it possible to render particles correctly on uneven terrain.

• Can be enabled for a particle system by using the new INI option IsGroundConforming.
• The feature can be enabled by using the define ENABLE_TERRAIN_CONFORMING_PARTICLES.
• Rendering ground-conforming particles correctly on bridges is out of scope.

Method

• The new class W3DTerrainParticle is a combination of (an evolved version of) W3DScorch and PointGroupClass.
• Produces meshes that have a matching topology with the terrain (except where the terrain is flat).
• Optimizes the mesh by making it coarse when the terrain is flat, using recursive subdivision.
• Makes use of batching see perf(particlesys): Batch same type particles to reduce cost of particle rendering by 15 to 30% #3155.

Testing

How-to

Using a test build

See this test build.

Using data patch

Building Patch2 with a modification to particle systems see the data PR.

Using code

Alternatively, you can cherry-pick this commit which force-enables the right particles:

git cherry-pick 22dcc0eed

Performance impact

The test build was used to test a moderately heavy scene (3 nuke cannons + 3 nukes shooting at a hill in Alpine Assault) using a Macbook Pro 2013 base spec aka Potato, which showed a 5.5% average FPS loss.

Graphics Settings	Resolution	Particle Rendering	FPS
Lowest	800x600	Original	57
Lowest	800x600	Conforming	56
Very High	800x600	Original	53
Very High	800x600	Conforming	50
Low	1920x1080	Original	24
Low	1920x1080	Conforming	24
Very High	1920x1080	Original	22
Very High	1920x1080	Conforming	20
Very High	3072x1920	Original	9
Very High	3072x1920	Conforming	8

Image gallery

More

Todo

• Add pull ID to commits
• Clean up commits after review
• Replicate in Generals