PIRL

Physically-Informed Rendering Layer

A high-performance, modular post-processing pipeline for edge detection and ambient occlusion in Godot.

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Overview

PIRL is a physically-informed screen-space rendering layer designed to enhance visual clarity and depth perception in real-time applications.

It combines depth-aware edge detection, ambient occlusion, and luminance-based fallback techniques into a unified, extensible pipeline built on top of Godot’s SubViewport architecture.

PIRL is engineered for developers who need precise visual control, predictable performance, and clean integration.

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Core Capabilities

• Geometric Edge Detection Detects true object boundaries using depth discontinuities.

• Screen-Space Ambient Occlusion (SSAO) Lightweight AO with tunable sampling and radius.

• Hybrid Edge Pipeline Combines depth + luminance for robust detection.

• Graceful Degradation Falls back to luminance-only mode when depth is unavailable.

• Modular Pass Design Easily extend or replace pipeline stages.

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Rendering Pipeline

Main Scene
 └── SubViewport_Scene
      ├── Color Buffer
      ├── Depth Buffer (optional)
           ↓
    SubViewport_PassA
      ├── Edge Detection
      ├── AO Computation
           ↓
        Output Texture

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Depth Access Strategies

Strategy	Description	Complexity	Performance	Notes
Spatial Extraction	Custom depth write via shader	Medium	High	Most control
hint_depth_texture	Built-in depth access	Low	Very High	Recommended
Luminance Only	No depth usage	Very Low	Maximum	Reduced accuracy

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Installation

git clone https://github.com/SepJs/PIRL.git

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Usage

1. Add a SubViewport for your main scene.
2. Configure a secondary SubViewport for PassA.
3. Attach PIRL shader to a full-screen quad.
4. Select your preferred depth strategy.
5. Tune parameters:

// Example uniforms
uniform float edge_threshold = 0.1;
uniform float ao_radius = 0.5;
uniform int ao_samples = 8;

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Performance Notes

• Designed for real-time rendering
• Scales from low-end (luminance) to high-quality (depth + AO)
• Minimal overhead when using hint_depth_texture
• No redundant geometry passes required

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Design Goals

• Deterministic visual output
• Minimal pipeline intrusion
• Explicit control over quality/performance
• Engine-native integration (no hacks)

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Roadmap

• Temporal stability (TAA integration)
• Multi-scale AO
• Edge-aware blur pass
• Debug visualization modes
• Vulkan-specific optimizations

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Contributing

Contributions are welcome, but should align with the project’s core principles:

• Performance-first
• Minimal abstraction overhead
• Clear shader logic

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License

MIT License

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Author

Developed by SepJs

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Final Note

PIRL is not just a shader— it’s a rendering layer abstraction for controlled, high-fidelity post-processing.