Forward+ scene pipeline

RenderForwardClustered implements Forward+ above RendererSceneRenderRD. It owns method-specific surface lists, instance data, pipeline selection, and scene pass orchestration. SceneShaderForwardClustered handles its shader and material representations.

Inputs and retained data

The shared scene path supplies RenderDataRD: camera/scene data, visible geometry, light/probe lists, atlases, environment, compositor, and output buffers. RenderBufferDataForwardClustered adds method-specific attachments and a ClusterBuilderRD to the output's custom data.

RenderGeometryInstance implementations cache the surface and dependency state used to build opaque, alpha, motion, and shadow work. A material or mesh change can invalidate that state before a draw occurs.

Cluster construction

ClusterBuilderRD receives light volumes, decals, and reflection probes. Its begin() resets view-specific state; bake_cluster() produces buffers consumed by scene shaders. Construction includes raster and compute work; describing it as only one compute dispatch misses the implementation's intermediate representation and passes.

The cluster buffer lets a shader find relevant elements for a screen region and depth range. It reduces how much light/probe/decal data each shaded fragment must consider. It does not replace CPU scene visibility or shadow caster selection.

Conditional pass sequence

_render_scene() selects required attachments and passes from material, environment, output, GI, antialiasing, and compositor flags. Its major stages include preparation, depth/normal/roughness work when needed, light/cluster/GI preparation, opaque drawing, sky/background, screen-space or separate-specular work, transparency, temporal processing, and output processing.

These are conditional stages rather than a single fixed pass list. Reflection probes use different buffers and skip work intended for the normal viewport. Debug modes and material screen/depth requirements also change the path.

Compositor callbacks appear at pre-opaque, post-opaque, post-sky, pre-transparent, and post-transparent positions. Requested color/depth resolves and extra attachments can add work around those points. A callback that asks for normal/roughness, motion vectors, albedo, or separate specular can affect earlier pass selection.

Pipeline selection

Surface drawing combines shader version, pass mode, vertex format, framebuffer format, blend/depth/raster state, and specialization choices. Compilation can be prepared in background tasks and counted by source. The render loop must still handle whether the required pipeline is available.

Scene shader code lives in the Forward+ shader family and shared lighting includes. Generated *ShaderRD wrappers feed ShaderRD; RD then creates backend-specific shader containers and pipelines. See shaders and caches.

Extension pressure

Adding a semantic pass currently means editing concrete orchestration, attachments, resource bindings, and shader/pipeline choices. The device graph will track submitted resource hazards, but it does not choose where that new scene stage belongs. This is a central distinction for proposals to simplify the scene pipeline.

Sources: Forward+ execution, method classes, cluster builder, and shader/effect entry points.