unity(particlesys): Merge Particle System code

[xezon]

Merge with Rebase

• Relates to GLA Terrorist suicide particle effects looks more spectacular in Generals GeneralsGamePatch#424
• Relates to Particles may not render at all if their Alpha min max values are zero GeneralsGamePatch#543
• Relates to Fix: Missing particle effects GeneralsGamePatch#809

This change merges all Particle System related code, including Particle Editor code. All individual changes are split into separate commits for best visibility.

Zero Hour gets

• Fix for erroneous particle visibility thresholds in Particle::isInvisible. This is the code fix for what this data fix attempted to workaround: Fix: Missing particle effects GeneralsGamePatch#809

Generals gets

• Removal of unused Drawable Particle Attachments
• Addition of ParticleSystem::setSkipParentXfrm
• Compile out of superfluous X and Y particle angles
• Addition of SMUDGE particle type (used for Microwave Tank effect)
• Optimization for particle update
• Optimization for wind motion particle update when disabled
• Change of math for aligning particle Z rotation with emitter direction

TODO

• Add pull id to commits

[greptile-apps]

Greptile Summary

This PR unifies particle system code between Generals and Zero Hour by merging features and optimizations.

Major Changes

• Removed Drawable Particle Attachments - Generals particle system no longer supports attaching Drawable objects to particles, aligning with Zero Hour architecture
• Compiled out X/Y rotation - Both versions now use PARTICLE_USE_XY_ROTATION=0 macro since particles only support billboard (camera-facing) and ground-aligned modes which only use Z-axis rotation
• Added SMUDGE particle type - New particle type for Microwave Tank effects in Generals
• Added setSkipParentXfrm() method - Allows particle systems already in world space to skip parent transform concatenation
• Fixed particle visibility thresholds - Zero Hour's isInvisible() now uses correct thresholds (0.01 instead of 0.02/0.06 for sum/product checks, changed to per-component checks)
• Optimized wind motion - Only processes wind motion when windMotion != WIND_MOTION_NOT_USED
• Optimized alpha updates - Skips alpha computation for ADDITIVE shader type particles
• Changed angle calculation - Replaced inline math with angleBetween() helper function for computing particle Z rotation aligned with emitter direction

Issues Found

• Performance issue in angleBetween() function: calls length() multiple times unnecessarily (2 calls in null check + 2 calls for actual calculation = 4 total sqrt operations instead of 2)

Confidence Score: 4/5

• This PR is safe to merge after fixing the performance issue in angleBetween()
• The changes are well-structured with clear separation into commits, and most are straightforward refactorings (removing unused drawable support, conditional compilation of unused X/Y rotation). The particle visibility threshold fix addresses a real bug. However, the angleBetween() function contains an inefficiency that calls expensive sqrt operations 4 times instead of 2, which impacts performance in every frame for particles with m_particleUpTowardsEmitter enabled.
• Both ParticleSys.cpp files need the angleBetween() performance fix before merge

Important Files Changed

Filename	Overview
Generals/Code/GameEngine/Include/GameClient/ParticleSys.h	Added PARTICLE_USE_XY_ROTATION macro, conditionally compiled X/Y rotation fields, added SMUDGE particle type, and setSkipParentXfrm method
Generals/Code/GameEngine/Source/GameClient/System/ParticleSys.cpp	Removed drawable particle support, conditionally compiled X/Y rotation code, optimized wind motion and alpha updates, changed angle calculation math - contains logic issue in angleBetween function
Generals/Code/GameEngine/Include/GameClient/Drawable.h	Removed particle system attachment methods and m_particle member field
GeneralsMD/Code/GameEngine/Source/GameClient/System/ParticleSys.cpp	Conditionally compiled X/Y rotation code, fixed particle visibility thresholds in isInvisible, improved whitespace formatting - contains logic issue in angleBetween function

Sequence Diagram

sequenceDiagram
    participant PS as ParticleSystem
    participant P as Particle
    participant PI as ParticleInfo
    participant D as Drawable (removed)
    
    Note over PS,D: Before: Particle System with Drawable Support
    PS->>PI: generateParticleInfo()
    PI->>P: new Particle(system, info)
    P->>D: Create Drawable if type==DRAWABLE
    D-->>P: Attach to particle
    P->>P: update() - update drawable position/rotation
    P->>D: setInstanceMatrix(), setPosition()
    
    Note over PS,D: After: Unified Particle System (No Drawables)
    PS->>PI: generateParticleInfo()
    Note over PI: X/Y rotation compiled out (PARTICLE_USE_XY_ROTATION=0)
    PI->>P: new Particle(system, info)
    Note over P,D: No drawable creation
    P->>P: update() - optimize wind motion check
    P->>P: update() - optimize alpha update (skip if ADDITIVE)
    P->>P: angleBetween() - calculate Z rotation for emitter direction
    
    Note over PS: Additional Optimizations
    PS->>PS: setSkipParentXfrm() - skip parent transform if in world space
    P->>P: isInvisible() - fixed thresholds (0.01 vs 0.02/0.06)

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[greptile-apps]

Additional Comments (2)

1. Generals/Code/GameEngine/Source/GameClient/System/ParticleSys.cpp, line 217-220 (link)

   logic: The null check calls length() twice per vector unnecessarily, then calls it again below. Since length() involves a square root calculation (sqrt(x*x + y*y)), this is wasteful. Calculate once and check for zero length:

2. GeneralsMD/Code/GameEngine/Source/GameClient/System/ParticleSys.cpp, line 217-220 (link)

   logic: The null check calls length() twice per vector unnecessarily, then calls it again below. Since length() involves a square root calculation (sqrt(x*x + y*y)), this is wasteful. Calculate once and check for zero length:

_{14 files reviewed, 2 comments}

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[xezon]

Very fair comment, but this is EA code and outside the scope of this change.

Edit: I have prepared an optimization for later.