Multipass shaders

apps/RenderCadenceCompositor/README.md

@@ -47,7 +47,9 @@ Included now:
 - shared-context GL prepare worker for runtime shader program compile/link
 - render-thread-only GL program swap once a prepared program is ready
 - manifest-driven stateless single-pass shader packages
-- HTTP shader list populated from supported stateless single-pass shader packages
+- manifest-driven stateless named-pass shader packages
+- atomic render-plan swap after every pass program is prepared
+- HTTP shader list populated from supported stateless full-frame shader packages
 - default float, vec2, color, boolean, enum, and trigger parameters
 - small JSON writer for future HTTP/WebSocket payloads
 - JSON serialization for cadence telemetry snapshots
@@ -60,7 +62,6 @@ Included now:
 Intentionally not included yet:
 
 - DeckLink input
-- multipass shader rendering
 - temporal/history/feedback shader storage
 - texture/LUT asset upload
 - text-parameter rasterization
@@ -86,6 +87,8 @@ This tracks parity with `apps/LoopThroughWithOpenGLCompositing`.
 - [x] Shared-context GL shader/program preparation
 - [x] Render-thread program swap at a frame boundary
 - [x] Stateless single-pass shader rendering
+- [x] Stateless named-pass shader rendering
+- [x] Atomic multipass render-plan commit
 - [x] Shader add/remove control path
 - [x] Previous-layer texture handoff for stacked shaders
 - [x] Supported shader list in HTTP/UI state
@@ -99,7 +102,6 @@ This tracks parity with `apps/LoopThroughWithOpenGLCompositing`.
 - [ ] DeckLink input capture
 - [ ] Input frame upload into the render scene
 - [ ] Live video input bound to `gVideoInput`
-- [ ] Multipass shader rendering
 - [ ] Temporal history buffers
 - [ ] Feedback buffers
 - [ ] Texture asset loading and upload
@@ -244,9 +246,12 @@ On startup the app begins compiling the selected shader package on a background
 
 The render thread keeps drawing the simple motion renderer while Slang compiles. It does not choose packages, launch Slang, or track build lifecycle. Once a completed shader artifact is published, the render-thread-owned runtime scene queues changed layers to a shared-context GL prepare worker. That worker compiles/links runtime shader programs off the cadence thread. The render thread only swaps in an already-prepared GL program at a frame boundary. If either the Slang build or GL preparation fails, the app keeps rendering the current renderer or simple motion fallback.
 
-Current runtime shader support is deliberately limited to stateless single-pass packages:
+Current runtime shader support is deliberately limited to stateless full-frame packages:
 
-- one pass only
+- one or more named passes
+- one sampled source input per pass
+- named intermediate outputs routed by the pass manifest
+- final visible output must be named `layerOutput`
 - no temporal history
 - no feedback storage
 - no texture/LUT assets yet
@@ -255,11 +260,11 @@ Current runtime shader support is deliberately limited to stateless single-pass
 - the first layer receives a small fallback source texture until DeckLink input is added
 - stacked layers receive the previous ready layer output through both `gVideoInput` and `gLayerInput`
 
-The `/api/state` shader list uses the same support rules as runtime shader compilation and reports only packages this app can run today. Unsupported manifest feature sets such as multipass, temporal, feedback, texture-backed, font-backed, or text-parameter shaders are hidden from the control UI for now.
+The `/api/state` shader list uses the same support rules as runtime shader compilation and reports only packages this app can run today. Unsupported manifest feature sets such as temporal, feedback, texture-backed, font-backed, or text-parameter shaders are hidden from the control UI for now.
 
 Runtime shaders are exposed through `RuntimeLayerModel` as display layers with manifest parameter defaults. The model also records whether each layer has a render-ready artifact. Add/remove POST controls mutate this app-owned model and may start background shader builds.
 
-When a layer becomes render-ready, the app publishes the ready render-layer snapshot to the render thread. The render thread owns the GL-side `RuntimeRenderScene`, diffs that snapshot at a frame boundary, queues new or changed programs to the shared-context prepare worker, swaps in prepared programs when available, removes obsolete GL programs, and renders ready layers in order. Stacked stateless full-frame shaders render through internal ping-pong targets so each layer can sample the previous layer through `gLayerInput`; the final ready layer renders to the output target.
+When a layer becomes render-ready, the app publishes the ready render-layer snapshot to the render thread. The render thread owns the GL-side `RuntimeRenderScene`, diffs that snapshot at a frame boundary, queues new or changed pass programs to the shared-context prepare worker, swaps in a full prepared render plan only after every pass is ready, removes obsolete GL programs, and renders ready layers in order. Stacked stateless full-frame shaders render through internal ping-pong targets so each layer can sample the previous layer through `gLayerInput`; multipass shaders route named intermediate outputs through their manifest-declared pass inputs, and the final ready layer renders to the output target.
 
 Successful handoff signs: