Render Pipeline

The EntropyPortal render pipeline is a Hybrid Phase-Based architecture. It explicitly phases high-level operations but uses a dynamic WorkGraph to parallelize the heavy lifting of command recording.

Data Flow

graph LR
    Sim[Simulation Thread] -->|Extract| BackBuf[RenderWorld Back]

    subgraph "Double Buffering"
        BackBuf
        FrontBuf[RenderWorld Front]
    end

    FrontBuf -->|Read| Render[Render Thread]

Execution Flow

graph TD
    Start([Begin Frame]) --> Sync[Swap Buffers & Sync]
    Sync --> Shadows[VSM Shadow Update]

    subgraph "Phase 1: Shadow & Prep"
        Shadows
        PrepBounds[Upload Bounds]
    end

    Shadows --> Probes[Probe Capture]

    subgraph "Phase 2: Global Illumination"
        Probes -->|Sequential| ProbeFaces[Render Probe Faces]
        ProbeFaces -->|Compute| ProbeFit[Spherical Gaussian Fit]
    end

    ProbeFit --> Cameras[Camera Job Scheduling]

    subgraph "Phase 3: Parallel Camera Views (Frame Graph)"
        Cameras --> AuxJobs[Auxiliary Cameras]
        AuxJobs -->|Dependency| MainJobs[Main Camera]

        subgraph "Auxiliary"
            AuxJobs
        end

        subgraph "Main"
            MainJobs
        end
    end

    MainJobs --> Composite[Composite]
    Composite --> Present([Present])

Key Stages

1. Preparation & Extraction

• ECS Sync: Camera identities are synchronized from the scene.
• Double-Buffering: The RenderWorld swaps buffers. The render thread reads from the immutable Front Buffer.

2. Virtual Shadow Maps (VSM)

Shadows are updated first and explicitly.

• View-Dependent: Shadow cascades are calculated for every camera view.
• Page Tables: GPU page tables are updated to map active shadow pages.

3. Probe Capture

Light probes (for GI) are updated sequentially.

• On-Demand: Only dirty probes are rendered.
• Fitting: Irradiance is projected into Spherical Gaussians (SG).

4. Camera Job Submission (The Frame Graph)

This is the core parallel stage using the WorkGraph.

1. Job Collection: RenderService iterates the RenderWorld to create FaceJob structures.
2. Graph Composition: jobs are added to the WorkGraph.
   • Aux Cameras are scheduled first.
   • Main Camera is scheduled with a dependency on Aux completion.
3. Parallel Recording: Worker threads record independent command buffers.
4. Batch Submission: The main thread submits all resulting buffers to the GPU queue.