Render Pipeline Architecture¶

This document describes the runtime render pipeline in detail: frame entry, route selection, stage execution, and fallback behavior.

Canonical Pipeline Entry Points¶

Frame entry: ../../modules/gaussian_splatting/renderer/gaussian_splat_renderer.cpp (render_scene_instance)
Streaming path orchestration: ../../modules/gaussian_splatting/renderer/render_streaming_orchestrator.cpp
Instancing execution mode decisions: ../../modules/gaussian_splatting/renderer/render_instancing_orchestrator.cpp
Stage runner interface: ../../modules/gaussian_splatting/renderer/render_pipeline_stages.h
Stage implementations: ../../modules/gaussian_splatting/renderer/render_pipeline_stages.cpp
Tile raster/resolve backend: ../../modules/gaussian_splatting/renderer/tile_render_stages.cpp

Frame Execution Flow¶

GaussianSplatRenderer::render_scene_instance initializes per-frame state and camera/view context.
Renderer decides route: streaming route via RenderStreamingOrchestrator when streaming buffers/readiness are valid, otherwise it records explicit not-ready/readiness state and skips the frame.
RenderPipelineStages runs stage sequence: cull (execute_cull_stage), sort (execute_sort_stage), then raster/composite (render_sorted_splats_with_context).
Output and diagnostics are finalized.

flowchart LR
    Entry[render_scene_instance] --> Route{Streaming<br/>ready?}
    Route -- Yes --> Stream[RenderStreamingOrchestrator]
    Route -- No --> NotReady[Publish not-ready state]
    Stream --> Cull[Cull Stage]
    Cull --> Sort[Sort Stage]
    Sort --> Raster[Raster / Composite]
    Raster --> Output[Final Output]

Execution Modes (Single-Pass vs Serial)¶

Instancing mode policy is controlled by project settings:

rendering/gaussian_splatting/instance_pipeline/true_single_pass_enabled
rendering/gaussian_splatting/instance_pipeline/benchmark_allow_serial_multi_asset

Mode behavior in orchestrators:

single_pass: production path (one cull/sort/raster chain for the frame)
serial: benchmark/diagnostic replay path when explicitly allowed
single_pass_forced: serial was requested but policy forced single-pass

Related sources:

Stage Contracts¶

Cull Stage¶

Inputs: view transform/projection + viewport + frame/provider context
Output: visible count and visible-domain information
Contract owner: RenderPipelineStages::CullStage

Sort Stage¶

Inputs: world-to-camera transform + cull outputs
Output: sorted indices and output-domain metadata
Contract owner: RenderPipelineStages::SortStage

Raster and Composite¶

RenderPipelineStages::render_sorted_splats_with_context prepares raster/composite inputs
TileRenderer performs tile pipeline and resolve passes
Output compositor handles final target/viewport handoff

Fallback and Failure Semantics¶

When prerequisites are missing (device, buffers, or readiness invariants), the renderer records explicit readiness state and avoids publishing invalid stage results.

Relevant code: