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
• Test all commits compile individually

[greptile-apps]

Greptile Overview

Greptile Summary

This PR unifies particle system code between Generals and Zero Hour by merging implementations and applying optimizations in both directions.

Key Changes:

• Compiles out unused X/Y particle rotation (PARTICLE_USE_XY_ROTATION=0) since particles only support Z-axis rotation due to billboard and ground-aligned rendering modes
• Removes drawable particle attachment system (unused feature) from Generals codebase
• Optimizes alpha updates by skipping calculations for ADDITIVE shader type
• Optimizes wind motion by checking if enabled before processing
• Fixes visibility threshold calculations in Particle::isInvisible (from 0.02f/0.06f to 0.01f and component checks)
• Adds SMUDGE particle type (used for Microwave Tank effect)
• Adds ParticleSystem::setSkipParentXfrm() method to disable parent transform application
• Refactors angleBetween function for cleaner implementation with pointer parameters
• Updates particle editor UI to respect PARTICLE_USE_XY_ROTATION macro

The changes are well-structured with individual commits for each logical change, making the merge history clear and reviewable.

Confidence Score: 4/5

• Safe to merge with minor performance optimization noted for follow-up
• Well-tested changes with clear commit history and logical separation of concerns. The only issue (redundant length calculations in angleBetween) is already acknowledged with a planned follow-up fix.
• No files require special attention - the redundant length calculation in Generals/Code/GameEngine/Source/GameClient/System/ParticleSys.cpp:3457 is already tracked for follow-up

Important Files Changed

Filename	Overview
Generals/Code/GameEngine/Source/GameClient/System/ParticleSys.cpp	Compiles out X/Y rotation support, optimizes alpha/wind updates, fixes visibility thresholds, adds SMUDGE type, refactors angleBetween function
GeneralsMD/Code/GameEngine/Source/GameClient/System/ParticleSys.cpp	Adds X/Y rotation guards, fixes visibility thresholds, improves formatting consistency
Generals/Code/GameEngine/Include/GameClient/ParticleSys.h	Adds PARTICLE_USE_XY_ROTATION macro, guards X/Y angle fields, adds SMUDGE type and setSkipParentXfrm method
GeneralsMD/Code/GameEngine/Include/GameClient/ParticleSys.h	Adds PARTICLE_USE_XY_ROTATION macro and guards X/Y angle fields for consistency with Generals

Sequence Diagram

sequenceDiagram
    participant PS as ParticleSystem
    participant P as Particle
    participant D as Drawable (removed)
    
    Note over PS,D: Particle System Update Flow
    
    PS->>PS: update()
    PS->>PS: updateWindMotion() [if enabled]
    PS->>PS: generateParticleInfo()
    PS->>P: new Particle(info)
    
    Note over P: Particle Update (per frame)
    P->>P: update()
    P->>P: Update position with velocity
    P->>P: doWindMotion() [if enabled]
    P->>P: Update orientation (Z-axis only)
    
    alt particleUpTowardsEmitter
        P->>P: angleBetween(&upVec, &emitterDir)
        P->>P: Set m_angleZ
    end
    
    alt Shader != ADDITIVE
        P->>P: Update alpha with keyframes
    end
    
    P->>P: Update size and color
    P->>P: isInvisible() check
    
    Note over D: Drawable particles removed
    Note over P: No m_drawable member
    Note over P: No X/Y rotation (PARTICLE_USE_XY_ROTATION=0)

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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}

_{Edit Code Review Agent Settings | Greptile}

[xezon]

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

Edit: I have prepared an optimization for later.

[greptile-apps]

Additional Comments (1)

1. GeneralsMD/Code/GameEngine/Source/GameClient/System/ParticleSys.cpp, line 3457-3459 (link)

   style: inefficient to compute vecA->length() and vecB->length() twice each - the guard condition calls .length(), then it's called again below

   _{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

_{14 files reviewed, 4 comments}

_{Edit Code Review Agent Settings | Greptile}

[Skyaero42]

Ok