perf(scene): Create light list iterators on the stack at points of use

[Mauller]

This PR helps with a performance issue caused by a non block allocated, heap based, memory allocation that occurs multiple times every frame.

BaseHeightMapRenderObjClass::getStaticDiffuse() was calling RTS3DScene::createLightsIterator() and destroyLightsIterator(RefRenderObjListIterator * it) to retrieve the LightList from the current RTS3DScene.

Since the RefRenderObjListIterator is not properly poolified in the W3D or GameMemory managers, it was causing the game memory manager to constantly acquire, zero, then release system memory.

In this tweak i added an extra function in RTS3DScene to retrieve a pointer to the LightList instead.
This then allowed a stack created RefRenderObjListIterator to be created within BaseHeightMapRenderObjClass::getStaticDiffuse() instead.

This then resulted in a 20-40% performance improvement at the start of the game depending on map.

EDIT:

I have updated this to also remove the create and destroy iterator functions. I then upated all current call sites to use a stack created iterator where necessary or removed using the iterator if it was unused.

[greptile-apps]

Greptile Summary

This PR removes heap allocation for scene-light iterators in terrain rendering. The main changes are:

• Adds access to the scene light list.
• Creates light iterators on the stack at use sites.
• Removes the obsolete iterator factory and destructor APIs.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
Core/GameEngineDevice/Source/W3DDevice/GameClient/BaseHeightMap.cpp	Uses a stack-local iterator while calculating static terrain lighting.
Core/GameEngineDevice/Source/W3DDevice/GameClient/W3DTerrainVisual.cpp	Removes the temporary scene-light iterator during terrain initialization.
Core/GameEngineDevice/Source/W3DDevice/GameClient/W3DView.cpp	Uses a stack-local iterator during terrain center updates.
Generals/Code/GameEngineDevice/Include/W3DDevice/GameClient/W3DScene.h	Exposes the embedded scene light list and removes obsolete iterator APIs.
Generals/Code/GameEngineDevice/Source/W3DDevice/GameClient/W3DScene.cpp	Removes obsolete heap-based iterator helper implementations.
GeneralsMD/Code/GameEngineDevice/Include/W3DDevice/GameClient/W3DScene.h	Keeps the Zero Hour scene interface aligned with the Generals variant.
GeneralsMD/Code/GameEngineDevice/Source/W3DDevice/GameClient/W3DScene.cpp	Removes the mirrored obsolete iterator helper implementations.

_{Reviews (3): Last reviewed commit: "perf(heighmap): Create light list iterat..." | Re-trigger Greptile}

[Mauller]

Flame graph showing before and after comparisons when loading Han Dynasty V3

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[Mauller]

Some ingame with overlay fps for comparisson.

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[xezon]

On my wip height map change I removed the entire thing.

If I recall correctly it is entirely unused.

[Mauller]

On my wip height map change I removed the entire thing.

If I recall correctly it is entirely unused.

Are you certain?

Need to check if its just unused in a lot of maps but used when point and directional lights are on a map.

[xezon]

Not 100% certain, but at the time I reworked height map I found no evidence that it is used for anything but is passed into many functions.

[Mauller]

Not 100% certain, but at the time I reworked height map I found no evidence that it is used for anything but is passed into many functions.

I think i remember some people wanting to add point and directional lights into the game again, so might be good to leave in the code for now but add this optimisation to get rid of the performance issue with it.

[Mauller]

Updated to remove the create and destroy iterator functions and all affected call sites.

[Skyaero42]

I like it

[Caball009]

@Mauller Could you rebase this branch?

@xezon I assume this hasn't been merged yet because it'd be superseded by your own changes eventually. Is that right? AFAICT it could have been merged two months ago, though.

[Mauller]

Rebased and tweaked