Combined Post-Process Implementation Guide

Implement Combined post-processing effects across three modules following the dependency chain: LumeRender → Lume3D → LumeScene

Task and Boundaries

This skill guides implementation of single-pass post-processing effects in OpenHarmony Graphics3D.

Applicable:

• Effects running in single fullscreen shader pass (tone mapping, color grading, vignette)
• Adding effects to Combined post-process system

Not Applicable:

• Effects requiring separate render passes (bloom with blur passes, depth-of-field, motion blur)

Module Dependency Overview

LumeRender (AGPRender)
    ↓
Lume3D (AGP3D)
    ↓
LumeScene

• LumeRender: Low-level rendering module, provides shader/render node infrastructure
• Lume3D: 3D scene module, provides ECS components, depends on LumeRender
• LumeScene: High-level scene module, provides user-friendly interfaces, depends on Lume3D

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Pre-Implementation Checklist

Before implementing any Combined post-process effect, ask yourself:

1. Visual Effect Goal: What visual effect do you want to achieve? (tone mapping, color grading, vignette, custom effect)
2. Parameter Complexity: How many parameters does the effect need?
   • 1-4 parameters: Use factors[] Vec4 only
   • 5-8 parameters: Split into factors[] + userFactors[]

   • 8 parameters: Consider if this is appropriate for Combined system

3. Render Pass Requirement: Does the effect need intermediate framebuffers?
   • Single fullscreen pass: ✓ Use Combined post-process (this skill)
   • Blur passes, downscale/upscale, temporal: ✗ Use multi-pass system (not this skill)
4. Index Availability: Are indices 0-7 available in Combined system?
   • Currently used: 0 (tone), 1 (vignette), 2 (dither), 3 (color conversion), 4 (fringe), 5 (upscale), 6 (white balance), 7 (color adjustments)
   • Need unused index: Must register new index in both shader and C++

Decision Tree:

Effect needs >4 params? ─────YES──→ Split: factors[] + userFactors[]
                         │
                         NO
                         ↓
Effect needs blur/temporal? ─YES──→ Use multi-pass system (EXIT this skill)
                         │
                         NO
                         ↓
Index 0-7 available? ──────YES──→ Continue with Combined implementation ✓
                         │
                         NO
                         ↓
Need to register new index → Follow LumeRender Step 1-3 first

Workflow

LumeRender (8 steps):

1. Define configuration structure
2. Register metadata
3. Define shader constants
4. Implement config-to-shader conversion
5. Fill post-process stack
6. Add conversion in RenderNodeUtil
7. Implement shader processing function
8. Integrate into render pipeline

Lume3D (5 steps):

1. Add flag bit
2. Define component property
3. Register metadata
4. Integrate into render system
5. Integrate into Lume3D shader

LumeScene (9 steps):

1. Define interface
2. Add to IPostProcess interface
3. Implement API wrapper
4. Implement effect class
5. Register in PostProcess
6. Register component type
7. Register plugin type
8. Register Any type
9. Update build files

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LumeRender Implementation

MANDATORY - READ ENTIRE FILE: Before starting LumeRender steps, you MUST read references/code_templates.md "LumeRender Templates" section (Steps 1-8, ~300 lines) completely. Do NOT set any range limits when reading this file.

Do NOT load advanced_reference.md yet — save for troubleshooting phase.

Step 1: Define Configuration Structure

File: api/render/datastore/render/render_data_store_render_pods.h

Define effect configuration struct with properties and default values. Add enum indices, flag bits, and property type declaration.

Details: See references/code_templates.md#step-1-define-configuration-structure

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Step 2: Register Metadata

File: src/postprocesses/render_post_process_combined_node.cpp

Register enum values, type metadata, and configuration structure metadata for reflection system.

Details: See references/code_templates.md#step-2-register-metadata

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Step 3: Define Shader Constants

File: api/render/shaders/common/render_post_process_structs_common.h

Define shader macro constants for effect specialization bits and indices.

Details: See references/code_templates.md#step-3-define-shader-constants

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Step 4: Implement Config-to-Shader Conversion

File: src/datastore/render_data_store_post_process.h

Implement conversion functions to pack configuration into shader-friendly Vec4 factors.

Details: See references/code_templates.md#step-4-implement-config-to-shader-conversion

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Step 5: Fill Post-Process Stack

File: src/datastore/render_data_store_post_process.cpp

Add effect to post-process stack with built-in data and factors.

Details: See references/code_templates.md#step-5-fill-post-process-stack

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Step 6: Add Conversion in RenderNodeUtil

File: src/nodecontext/render_node_util.cpp

Add factor conversion call in GetRenderPostProcessConfiguration() function.

Details: See references/code_templates.md#step-6-add-conversion-in-rendernodeutil

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Step 7: Implement Shader Processing Function

File: api/render/shaders/common/render_post_process_blocks.h

Implement GLSL shader processing function with effect logic.

Details: See references/code_templates.md#step-7-implement-shader-processing-function

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Step 8: Integrate into Render Pipeline

File: assets/render/shaders/shader/fullscreen_combined_post_process.frag

Call shader processing function in fullscreen render pipeline.

Details: See references/code_templates.md#step-8-integrate-into-render-pipeline

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Lume3D Implementation

MANDATORY - READ SECTION: Now read references/code_templates.md "Lume3D Templates" section (Steps 1-5, ~100 lines) for ECS integration examples.

Do NOT load advanced_reference.md yet — continue following workflow steps.

Step 1: Add Flag Bit

File: api/3d/ecs/components/post_process_component.h

Add flag bit to PostProcessComponent::FlagBits enum.

Details: See references/code_templates.md#lume3d-step-1-add-flag-bit

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Step 2: Define Component Property

File: api/3d/ecs/components/post_process_component.h

Define component property with DEFINE_PROPERTY macro.

Details: See references/code_templates.md#lume3d-step-2-define-component-property

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Step 3: Register Metadata

File: src/ecs/components/post_process_component_manager.cpp

Register enum values and configuration metadata.

Details: See references/code_templates.md#lume3d-step-3-register-metadata

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Step 4: Integrate into Render System

File: src/ecs/systems/render_system.cpp

Assign configuration in ProcessPostProcessComponents() function.

Details: See references/code_templates.md#lume3d-step-4-integrate-into-render-system

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Step 5: Integrate into Lume3D Shader

File: api/3d/shaders/common/3d_dm_inplace_post_process.h

Call shader processing function in Lume3D inplace post-process.

Details: See references/code_templates.md#lume3d-step-5-integrate-into-lume3d-shader

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LumeScene Implementation

MANDATORY - READ SECTION: Read references/code_templates.md "LumeScene Templates" section (Steps 1-9, ~400 lines) for API wrapper and registration examples.

Do NOT load advanced_reference.md yet — only load when encountering errors or need data flow diagrams.

Step 1: Define Interface

File: include/scene/interface/postprocess/intf_your_effect.h

Define interface class with META_INTERFACE and property declarations.

Details: See references/code_templates.md#lumescene-step-1-define-interface

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Step 2: Add to IPostProcess Interface

File: include/scene/interface/intf_postprocess.h

Add include and META_READONLY_PROPERTY for effect interface.

Details: See references/code_templates.md#lumescene-step-2-add-to-ipostprocess-interface

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Step 3: Implement API Wrapper

File: include/scene/api/post_process.h

Implement wrapper class with META_INTERFACE_OBJECT and property macros.

Details: See references/code_templates.md#lumescene-step-3-implement-api-wrapper

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Step 4: Implement Effect Class

Files:

• Header: src/postprocess/your_effect.h
• Implementation: src/postprocess/your_effect.cpp

Implement effect class inheriting from PostProcessEffect template with META_OBJECT macros.

Details: See references/code_templates.md#lumescene-step-4-implement-effect-class

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Step 5: Register in PostProcess

Files:

• Header: src/postprocess/postprocess.h
• Implementation: src/postprocess/postprocess.cpp

Add static property data and InitDynamicProperty handler.

Details: See references/code_templates.md#lumescene-step-5-register-in-postprocess

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Step 6: Register Component Type

File: src/component/postprocess_component.h

Add META_TYPE registration and property macros.

Details: See references/code_templates.md#lumescene-step-6-register-component-type

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Step 7: Register Plugin Type

File: src/plugin.cpp

Add RegisterObjectType and UnregisterObjectType calls.

Details: See references/code_templates.md#lumescene-step-7-register-plugin-type

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Step 8: Register Any Type

File: src/register_anys.cpp

Add interface pointer type to ObjectTypes list.

Details: See references/code_templates.md#lumescene-step-8-register-any-type

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Step 9: Update Build Files

Files:

• include/CMakeLists.txt
• src/CMakeLists.txt
• BUILD.gn

Add interface and source files to build targets.

Details: See references/code_templates.md#lumescene-step-9-update-build-files

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Prohibited Practices

NEVER Apply to Multi-Pass Effects

Effects requiring separate render passes (bloom with blur, depth-of-field, motion blur, FXAA, TAA):

• WHY: Combined post-process shader (fullscreen_combined_post_process.frag) only handles indices 0-7. Multi-pass effects use indices 8+ with separate shaders and intermediate framebuffers.
• CONSEQUENCE: Attempting Combined approach causes factors[INDEX_BLOOM] (index 9) to be ignored in Combined shader. Effect won't render, or may read garbage data from wrong memory offset.
• VALIDATION: Check if effect needs intermediate render passes (blur passes, downscale/upscale). If yes → use multi-pass system, not Combined.
• CORRECT: Use dedicated multi-pass post-process implementation with separate render node graph.

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NEVER Mismatch Shader-C++ Indices

Index consistency between GLSL constants and C++ enums:

• WHY: Shader accesses uGlobalData.factors[POST_PROCESS_INDEX_TONEMAP] directly. If shader defines POST_PROCESS_INDEX_TONEMAP 0 but C++ defines INDEX_TONEMAP 1, shader reads wrong Vec4 from factors array.
• CONSEQUENCE: Visual artifacts (wrong colors, parameters not applied) or GPU validation error "array index out of bounds" if index exceeds POST_PROCESS_GLOBAL_VEC4_FACTOR_COUNT (14).
• VALIDATION: Cross-check three files:
  1. Shader: render_post_process_structs_common.h → POST_PROCESS_INDEX_* values
  2. C++ config: render_data_store_render_pods.h → PostProcessConfiguration::INDEX_* values
  3. DataStore conversion: render_data_store_post_process.cpp → factors[INDEX_*] assignment
• CORRECT: Ensure all three locations use same numeric value. File comment explicitly states: "needs to match api/core/render/render_data_store_render_pods.h".

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NEVER Forget userFactors for >4 Parameters

Effects needing more than 4 float parameters:

• WHY: Vec4 only holds 4 floats. GlobalPostProcessStruct has factors[14] (Vec4 array) and userFactors[16] (Vec4 array). If effect has 5+ parameters, must split into factors + userFactors.
• CONSEQUENCE: Shader tries to read uGlobalData.userFactors[USER_INDEX_*] but constant undefined → compilation error "undefined macro". Or if defined but not filled → shader reads zero Vec4 → effect parameters wrong.
• VALIDATION: Count effect parameters. If >4, verify:
  1. USER_INDEX_* constant defined in render_data_store_render_pods.h
  2. GetFactorXXX() function for userFactors in render_data_store_post_process.h
  3. Shader uses correct userFactors index: uGlobalData.userFactors[POST_PROCESS_USER_INDEX_*]
• CORRECT: For 5-8 parameters: use factors[0-3] + userFactors[0-3]. Define USER_INDEX_* constant, implement conversion function, call in FillDefaultPostProcessData.

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NEVER Skip LumeRender/Lume3D/LumeScene Consistency

All three modules must be updated:

• WHY: Combined post-process flows through three modules: LumeRender defines shader constants → Lume3D integrates into ECS → LumeScene wraps API. Skipping one module breaks the chain.
• CONSEQUENCE:
  • Skip LumeRender: Shader can't find PostProcessXXXBlock() function → compilation error
  • Skip Lume3D: PostProcessComponent missing property → ECS system won't propagate configuration → shader receives zero factors
  • Skip LumeScene: User API missing → developers can't configure effect → unusable
• VALIDATION: Use implementation checklist (22 steps across 3 modules). Check each module's key files exist and are modified.
• CORRECT: Follow all 22 steps. LumeRender (8) → Lume3D (5) → LumeScene (9) in sequence.

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Exceptions and Fallbacks

Effect Requires Multiple Render Passes

Symptom: Effect needs blur passes, downscale/upscale, temporal accumulation.

• Fallback: This skill doesn't apply. Use dedicated multi-pass post-process system with separate render node graph.
• Evidence: Check if shader needs uImgSampler + uBloomSampler + intermediate framebuffers (like bloom). If yes → multi-pass.

Shader Compilation Error

Symptom: "undefined macro POST_PROCESS_INDEX_XXX" or "array index out of bounds".

• Diagnosis: Index mismatch or missing constant definition.
• Fix: Check shader constant matches C++ enum value. Verify index < 14 (POST_PROCESS_GLOBAL_VEC4_FACTOR_COUNT).

Visual Artifacts or Effect Not Applied

Symptom: Wrong colors, parameters ignored, effect invisible.

• Diagnosis: Wrong factors index, or GetFactorXXX() not called in DataStore.
• Fix: Verify conversion function called in both render_data_store_post_process.cpp (Step 5) and render_node_util.cpp (Step 6).

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References

Primary Reference Files

• references/code_templates.md (785 lines): Complete code templates with Generic Template and Tone Mapping Example for all 22 steps. MANDATORY loading during implementation.
• references/advanced_reference.md (306 lines): Advanced reference with data flow diagrams, implementation checklists, and troubleshooting guide. Load ONLY when troubleshooting or need data flow understanding.

Loading Strategy

Phase 1 - Initial Implementation:

• ✅ MANDATORY: Load code_templates.md in three stages (LumeRender → Lume3D → LumeScene sections)
• ❌ Do NOT load: advanced_reference.md (save for later)

Phase 2 - Troubleshooting:

• ✅ Load when needed: advanced_reference.md if encountering errors, need data flow diagrams, or implementation checklists
• ❌ Do NOT reload: code_templates.md if already loaded

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Key Points

1. Architecture: Configuration-Conversion Separation

   • Configuration structs for user interfaces
   • Conversion functions pack into shader-friendly Vec4

2. Critical: Shader-C++ Index/Bit Consistency

   • POST_PROCESS_INDEX_* ↔ PostProcessConfiguration::INDEX_*
   • POST_PROCESS_SPECIALIZATION_*_BIT ↔ FlagBits enum
   • Mismatch causes GPU validation errors or visual artifacts

3. Mandatory: Dual Path Support

   • Add conversions in BOTH DataStore (Step 5) AND RenderNodeUtil (Step 6)
   • Single-path implementation fails in some scenarios

4. Naming and Macro Conventions

   • Shader function: PostProcess<Effect>Block naming
   • META_TYPE: include only when interface has enum types
   • META_READONLY_PROPERTY: must add to IPostProcess interface