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:
 

apps/RenderCadenceCompositor/render/runtime/RuntimeRenderScene.cpp

@@ -39,14 +39,18 @@ bool RuntimeRenderScene::CommitRenderLayers(const std::vector<RenderCadenceCompo
 			continue;
 		}
 
-		if (layerIt->renderer)
+		for (LayerProgram::PassProgram& pass : layerIt->passes)
-			layerIt->renderer->ShutdownGl();
+		{
+			if (pass.renderer)
+				pass.renderer->ShutdownGl();
+		}
+		ReleasePendingPrograms(*layerIt);
 		layerIt = mLayers.erase(layerIt);
 	}
 
 	for (const RenderCadenceCompositor::RuntimeRenderLayerModel& layer : layers)
 	{
-		if (layer.artifact.fragmentShaderSource.empty())
+		if (layer.artifact.passes.empty() && layer.artifact.fragmentShaderSource.empty())
 			continue;
 
 		const std::string fingerprint = Fingerprint(layer.artifact);
@@ -55,16 +59,25 @@ bool RuntimeRenderScene::CommitRenderLayers(const std::vector<RenderCadenceCompo
 		{
 			LayerProgram next;
 			next.layerId = layer.id;
-			next.renderer = std::make_unique<RuntimeShaderRenderer>();
 			mLayers.push_back(std::move(next));
 			program = &mLayers.back();
 		}
 
-		if (program->shaderId == layer.shaderId && program->sourceFingerprint == fingerprint && program->renderer && program->renderer->HasProgram())
+		bool hasReadyPass = false;
+		for (const LayerProgram::PassProgram& pass : program->passes)
+		{
+			if (pass.renderer && pass.renderer->HasProgram())
+			{
+				hasReadyPass = true;
+				break;
+			}
+		}
+		if (program->shaderId == layer.shaderId && program->sourceFingerprint == fingerprint && hasReadyPass)
 			continue;
 		if (program->pendingFingerprint == fingerprint)
 			continue;
 
+		ReleasePendingPrograms(*program);
 		program->shaderId = layer.shaderId;
 		program->pendingFingerprint = fingerprint;
 		layersToPrepare.push_back(layer);
@@ -84,8 +97,13 @@ bool RuntimeRenderScene::HasLayers()
 	for (const std::string& layerId : mLayerOrder)
 	{
 		const LayerProgram* layer = FindLayer(layerId);
-		if (layer && layer->renderer && layer->renderer->HasProgram())
+		if (!layer)
-			return true;
+			continue;
+		for (const LayerProgram::PassProgram& pass : layer->passes)
+		{
+			if (pass.renderer && pass.renderer->HasProgram())
+				return true;
+		}
 	}
 	return false;
 }
@@ -98,9 +116,16 @@ void RuntimeRenderScene::RenderFrame(uint64_t frameIndex, unsigned width, unsign
 	for (const std::string& layerId : mLayerOrder)
 	{
 		LayerProgram* layer = FindLayer(layerId);
-		if (!layer || !layer->renderer || !layer->renderer->HasProgram())
+		if (!layer)
 			continue;
-		readyLayers.push_back(layer);
+		for (const LayerProgram::PassProgram& pass : layer->passes)
+		{
+			if (pass.renderer && pass.renderer->HasProgram())
+			{
+				readyLayers.push_back(layer);
+				break;
+			}
+		}
 	}
 
 	if (readyLayers.empty())
@@ -111,14 +136,14 @@ void RuntimeRenderScene::RenderFrame(uint64_t frameIndex, unsigned width, unsign
 
 	if (readyLayers.size() == 1)
 	{
-		readyLayers.front()->renderer->RenderFrame(frameIndex, width, height);
+		RenderLayer(*readyLayers.front(), frameIndex, width, height, 0, static_cast<GLuint>(outputFramebuffer), true);
 		return;
 	}
 
 	if (!EnsureLayerTargets(width, height))
 	{
 		glBindFramebuffer(GL_FRAMEBUFFER, static_cast<GLuint>(outputFramebuffer));
-		readyLayers.back()->renderer->RenderFrame(frameIndex, width, height);
+		RenderLayer(*readyLayers.back(), frameIndex, width, height, 0, static_cast<GLuint>(outputFramebuffer), true);
 		return;
 	}
 
@@ -130,12 +155,11 @@ void RuntimeRenderScene::RenderFrame(uint64_t frameIndex, unsigned width, unsign
 		if (isFinalLayer)
 		{
 			glBindFramebuffer(GL_FRAMEBUFFER, static_cast<GLuint>(outputFramebuffer));
-			readyLayers[layerIndex]->renderer->RenderFrame(frameIndex, width, height, layerInputTexture, layerInputTexture);
+			RenderLayer(*readyLayers[layerIndex], frameIndex, width, height, layerInputTexture, static_cast<GLuint>(outputFramebuffer), true);
 			continue;
 		}
 
-		glBindFramebuffer(GL_FRAMEBUFFER, mLayerFramebuffers[nextTargetIndex]);
+		RenderLayer(*readyLayers[layerIndex], frameIndex, width, height, layerInputTexture, mLayerFramebuffers[nextTargetIndex], true);
-		readyLayers[layerIndex]->renderer->RenderFrame(frameIndex, width, height, layerInputTexture, layerInputTexture);
 		layerInputTexture = mLayerTextures[nextTargetIndex];
 		nextTargetIndex = 1 - nextTargetIndex;
 	}
@@ -146,8 +170,12 @@ void RuntimeRenderScene::ShutdownGl()
 	mPrepareWorker.Stop();
 	for (LayerProgram& layer : mLayers)
 	{
-		if (layer.renderer)
+		for (LayerProgram::PassProgram& pass : layer.passes)
-			layer.renderer->ShutdownGl();
+		{
+			if (pass.renderer)
+				pass.renderer->ShutdownGl();
+		}
+		ReleasePendingPrograms(layer);
 	}
 	mLayers.clear();
 	mLayerOrder.clear();
@@ -172,28 +200,165 @@ void RuntimeRenderScene::ConsumePreparedPrograms()
 			continue;
 		}
 
+		bool replacesExistingPendingPass = false;
+		for (RuntimePreparedShaderProgram& existing : layer->pendingPreparedPrograms)
+		{
+			if (existing.passId != preparedProgram.passId)
+				continue;
+			existing.ReleaseGl();
+			existing = std::move(preparedProgram);
+			replacesExistingPendingPass = true;
+			break;
+		}
+		if (!replacesExistingPendingPass)
+			layer->pendingPreparedPrograms.push_back(std::move(preparedProgram));
+		TryCommitPendingPrograms(*layer);
+	}
+}
+
+void RuntimeRenderScene::ReleasePendingPrograms(LayerProgram& layer)
+{
+	for (RuntimePreparedShaderProgram& program : layer.pendingPreparedPrograms)
+		program.ReleaseGl();
+	layer.pendingPreparedPrograms.clear();
+}
+
+void RuntimeRenderScene::TryCommitPendingPrograms(LayerProgram& layer)
+{
+	if (layer.pendingPreparedPrograms.empty())
+		return;
+
+	const RuntimeShaderArtifact& artifact = layer.pendingPreparedPrograms.front().artifact;
+	const std::size_t expectedPassCount = artifact.passes.empty() ? 1 : artifact.passes.size();
+	if (layer.pendingPreparedPrograms.size() < expectedPassCount)
+		return;
+
+	std::vector<LayerProgram::PassProgram> nextPasses;
+	nextPasses.reserve(expectedPassCount);
+	for (const RuntimeShaderPassArtifact& passArtifact : artifact.passes)
+	{
+		auto preparedIt = std::find_if(
+			layer.pendingPreparedPrograms.begin(),
+			layer.pendingPreparedPrograms.end(),
+			[&passArtifact](const RuntimePreparedShaderProgram& prepared) {
+				return prepared.passId == passArtifact.passId;
+			});
+		if (preparedIt == layer.pendingPreparedPrograms.end())
+			return;
+
 		std::unique_ptr<RuntimeShaderRenderer> nextRenderer = std::make_unique<RuntimeShaderRenderer>();
 		std::string error;
-		if (!nextRenderer->CommitPreparedProgram(preparedProgram, error))
+		if (!nextRenderer->CommitPreparedProgram(*preparedIt, error))
 		{
-			preparedProgram.ReleaseGl();
+			ReleasePendingPrograms(layer);
+			return;
+		}
+
+		LayerProgram::PassProgram nextPass;
+		nextPass.passId = preparedIt->passId;
+		nextPass.inputNames = preparedIt->inputNames;
+		nextPass.outputName = preparedIt->outputName.empty() ? preparedIt->passId : preparedIt->outputName;
+		nextPass.renderer = std::move(nextRenderer);
+		nextPasses.push_back(std::move(nextPass));
+	}
+	if (artifact.passes.empty())
+	{
+		RuntimePreparedShaderProgram& prepared = layer.pendingPreparedPrograms.front();
+		std::unique_ptr<RuntimeShaderRenderer> nextRenderer = std::make_unique<RuntimeShaderRenderer>();
+		std::string error;
+		if (!nextRenderer->CommitPreparedProgram(prepared, error))
+		{
+			ReleasePendingPrograms(layer);
+			return;
+		}
+
+		LayerProgram::PassProgram nextPass;
+		nextPass.passId = prepared.passId;
+		nextPass.inputNames = prepared.inputNames;
+		nextPass.outputName = prepared.outputName.empty() ? prepared.passId : prepared.outputName;
+		nextPass.renderer = std::move(nextRenderer);
+		nextPasses.push_back(std::move(nextPass));
+	}
+
+	for (LayerProgram::PassProgram& pass : layer.passes)
+	{
+		if (pass.renderer)
+			pass.renderer->ShutdownGl();
+	}
+	layer.passes = std::move(nextPasses);
+	layer.shaderId = artifact.shaderId;
+	layer.sourceFingerprint = layer.pendingPreparedPrograms.front().sourceFingerprint;
+	layer.pendingFingerprint.clear();
+	layer.pendingPreparedPrograms.clear();
+}
+
+GLuint RuntimeRenderScene::RenderLayer(
+	LayerProgram& layer,
+	uint64_t frameIndex,
+	unsigned width,
+	unsigned height,
+	GLuint layerInputTexture,
+	GLuint outputFramebuffer,
+	bool renderToOutput)
+{
+	GLuint namedOutputs[2] = {};
+	std::string namedOutputNames[2];
+	std::size_t nextTargetIndex = 2;
+	GLuint lastOutputTexture = layerInputTexture;
+
+	for (LayerProgram::PassProgram& pass : layer.passes)
+	{
+		if (!pass.renderer || !pass.renderer->HasProgram())
+			continue;
+
+		GLuint sourceTexture = layerInputTexture;
+		if (!pass.inputNames.empty())
+		{
+			const std::string& inputName = pass.inputNames.front();
+			if (inputName != "layerInput" && inputName != "videoInput")
+			{
+				for (std::size_t index = 0; index < 2; ++index)
+				{
+					if (namedOutputNames[index] == inputName)
+					{
+						sourceTexture = namedOutputs[index];
+						break;
+					}
+				}
+			}
+		}
+
+		const bool writesLayerOutput = pass.outputName == "layerOutput";
+		if (writesLayerOutput && renderToOutput)
+		{
+			glBindFramebuffer(GL_FRAMEBUFFER, outputFramebuffer);
+			pass.renderer->RenderFrame(frameIndex, width, height, sourceTexture, sourceTexture);
+			lastOutputTexture = 0;
 			continue;
 		}
 
-		if (layer->renderer)
+		if (!EnsureLayerTargets(width, height))
-			layer->renderer->ShutdownGl();
+			continue;
-		layer->renderer = std::move(nextRenderer);
+
-		layer->shaderId = preparedProgram.shaderId;
+		const std::size_t targetIndex = nextTargetIndex;
-		layer->sourceFingerprint = preparedProgram.sourceFingerprint;
+		nextTargetIndex = nextTargetIndex == 2 ? 3 : 2;
-		layer->pendingFingerprint.clear();
+		glBindFramebuffer(GL_FRAMEBUFFER, mLayerFramebuffers[targetIndex]);
+		pass.renderer->RenderFrame(frameIndex, width, height, sourceTexture, sourceTexture);
+		const std::size_t namedIndex = targetIndex - 2;
+		namedOutputs[namedIndex] = mLayerTextures[targetIndex];
+		namedOutputNames[namedIndex] = pass.outputName;
+		lastOutputTexture = mLayerTextures[targetIndex];
 	}
+
+	return lastOutputTexture;
 }
 
 bool RuntimeRenderScene::EnsureLayerTargets(unsigned width, unsigned height)
 {
 	if (width == 0 || height == 0)
 		return false;
-	if (mLayerFramebuffers[0] != 0 && mLayerFramebuffers[1] != 0 && mLayerTextures[0] != 0 && mLayerTextures[1] != 0
+	if (mLayerFramebuffers[0] != 0 && mLayerFramebuffers[1] != 0 && mLayerFramebuffers[2] != 0 && mLayerFramebuffers[3] != 0
+		&& mLayerTextures[0] != 0 && mLayerTextures[1] != 0 && mLayerTextures[2] != 0 && mLayerTextures[3] != 0
 		&& mLayerTargetWidth == width && mLayerTargetHeight == height)
 		return true;
 
@@ -201,9 +366,9 @@ bool RuntimeRenderScene::EnsureLayerTargets(unsigned width, unsigned height)
 	mLayerTargetWidth = width;
 	mLayerTargetHeight = height;
 
-	glGenFramebuffers(2, mLayerFramebuffers);
+	glGenFramebuffers(4, mLayerFramebuffers);
-	glGenTextures(2, mLayerTextures);
+	glGenTextures(4, mLayerTextures);
-	for (int index = 0; index < 2; ++index)
+	for (int index = 0; index < 4; ++index)
 	{
 		glBindTexture(GL_TEXTURE_2D, mLayerTextures[index]);
 		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
@@ -239,14 +404,15 @@ bool RuntimeRenderScene::EnsureLayerTargets(unsigned width, unsigned height)
 
 void RuntimeRenderScene::DestroyLayerTargets()
 {
-	if (mLayerFramebuffers[0] != 0 || mLayerFramebuffers[1] != 0)
+	if (mLayerFramebuffers[0] != 0 || mLayerFramebuffers[1] != 0 || mLayerFramebuffers[2] != 0 || mLayerFramebuffers[3] != 0)
-		glDeleteFramebuffers(2, mLayerFramebuffers);
+		glDeleteFramebuffers(4, mLayerFramebuffers);
-	if (mLayerTextures[0] != 0 || mLayerTextures[1] != 0)
+	if (mLayerTextures[0] != 0 || mLayerTextures[1] != 0 || mLayerTextures[2] != 0 || mLayerTextures[3] != 0)
-		glDeleteTextures(2, mLayerTextures);
+		glDeleteTextures(4, mLayerTextures);
-	mLayerFramebuffers[0] = 0;
+	for (int index = 0; index < 4; ++index)
-	mLayerFramebuffers[1] = 0;
+	{
-	mLayerTextures[0] = 0;
+		mLayerFramebuffers[index] = 0;
-	mLayerTextures[1] = 0;
+		mLayerTextures[index] = 0;
+	}
 	mLayerTargetWidth = 0;
 	mLayerTargetHeight = 0;
 }
@@ -271,8 +437,23 @@ const RuntimeRenderScene::LayerProgram* RuntimeRenderScene::FindLayer(const std:
 	return nullptr;
 }
 
+RuntimeRenderScene::LayerProgram::PassProgram* RuntimeRenderScene::FindPass(LayerProgram& layer, const std::string& passId)
+{
+	for (LayerProgram::PassProgram& pass : layer.passes)
+	{
+		if (pass.passId == passId)
+			return &pass;
+	}
+	return nullptr;
+}
+
 std::string RuntimeRenderScene::Fingerprint(const RuntimeShaderArtifact& artifact)
 {
 	const std::hash<std::string> hasher;
-	return artifact.shaderId + ":" + std::to_string(artifact.fragmentShaderSource.size()) + ":" + std::to_string(hasher(artifact.fragmentShaderSource));
+	std::string source;
+	for (const RuntimeShaderPassArtifact& pass : artifact.passes)
+		source += pass.passId + ":" + pass.outputName + ":" + pass.fragmentShaderSource + "\n";
+	if (source.empty())
+		source = artifact.fragmentShaderSource;
+	return artifact.shaderId + ":" + std::to_string(source.size()) + ":" + std::to_string(hasher(source));
 }

apps/RenderCadenceCompositor/render/runtime/RuntimeRenderScene.h

@@ -32,21 +32,33 @@ private:
 		std::string shaderId;
 		std::string sourceFingerprint;
 		std::string pendingFingerprint;
-		std::unique_ptr<RuntimeShaderRenderer> renderer;
+		std::vector<RuntimePreparedShaderProgram> pendingPreparedPrograms;
+		struct PassProgram
+		{
+			std::string passId;
+			std::vector<std::string> inputNames;
+			std::string outputName;
+			std::unique_ptr<RuntimeShaderRenderer> renderer;
+		};
+		std::vector<PassProgram> passes;
 	};
 
 	void ConsumePreparedPrograms();
+	void ReleasePendingPrograms(LayerProgram& layer);
+	void TryCommitPendingPrograms(LayerProgram& layer);
 	bool EnsureLayerTargets(unsigned width, unsigned height);
 	void DestroyLayerTargets();
+	GLuint RenderLayer(LayerProgram& layer, uint64_t frameIndex, unsigned width, unsigned height, GLuint layerInputTexture, GLuint outputFramebuffer, bool renderToOutput);
 	LayerProgram* FindLayer(const std::string& layerId);
 	const LayerProgram* FindLayer(const std::string& layerId) const;
+	LayerProgram::PassProgram* FindPass(LayerProgram& layer, const std::string& passId);
 	static std::string Fingerprint(const RuntimeShaderArtifact& artifact);
 
 	RuntimeShaderPrepareWorker mPrepareWorker;
 	std::vector<LayerProgram> mLayers;
 	std::vector<std::string> mLayerOrder;
-	GLuint mLayerFramebuffers[2] = {};
+	GLuint mLayerFramebuffers[4] = {};
-	GLuint mLayerTextures[2] = {};
+	GLuint mLayerTextures[4] = {};
 	unsigned mLayerTargetWidth = 0;
 	unsigned mLayerTargetHeight = 0;
 };

apps/RenderCadenceCompositor/render/runtime/RuntimeShaderPrepareWorker.cpp

@@ -77,20 +77,35 @@ void RuntimeShaderPrepareWorker::Submit(const std::vector<RenderCadenceComposito
 	std::lock_guard<std::mutex> lock(mMutex);
 	for (const RenderCadenceCompositor::RuntimeRenderLayerModel& layer : layers)
 	{
-		if (layer.artifact.fragmentShaderSource.empty())
+		if (layer.artifact.passes.empty() && layer.artifact.fragmentShaderSource.empty())
 			continue;
 
-		PrepareRequest request;
+		std::vector<RuntimeShaderPassArtifact> passes = layer.artifact.passes;
-		request.layerId = layer.id;
+		if (passes.empty())
-		request.shaderId = layer.shaderId;
+		{
-		request.sourceFingerprint = Fingerprint(layer.artifact);
+			RuntimeShaderPassArtifact pass;
-		request.artifact = layer.artifact;
+			pass.passId = "main";
+			pass.fragmentShaderSource = layer.artifact.fragmentShaderSource;
+			pass.outputName = "layerOutput";
+			passes.push_back(std::move(pass));
+		}
 
-		auto sameLayer = [&request](const PrepareRequest& existing) {
+		auto sameLayer = [&layer](const PrepareRequest& existing) {
-			return existing.layerId == request.layerId;
+			return existing.layerId == layer.id;
 		};
 		mRequests.erase(std::remove_if(mRequests.begin(), mRequests.end(), sameLayer), mRequests.end());
-		mRequests.push_back(std::move(request));
+
+		for (const RuntimeShaderPassArtifact& pass : passes)
+		{
+			PrepareRequest request;
+			request.layerId = layer.id;
+			request.shaderId = layer.shaderId;
+			request.passId = pass.passId;
+			request.sourceFingerprint = Fingerprint(layer.artifact);
+			request.artifact = layer.artifact;
+			request.passArtifact = pass;
+			mRequests.push_back(std::move(request));
+		}
 	}
 	mCondition.notify_one();
 }
@@ -137,10 +152,11 @@ void RuntimeShaderPrepareWorker::ThreadMain()
 		}
 
 		RuntimePreparedShaderProgram preparedProgram;
-		RuntimeShaderRenderer::BuildPreparedProgram(
+		RuntimeShaderRenderer::BuildPreparedPassProgram(
 			request.layerId,
 			request.sourceFingerprint,
 			request.artifact,
+			request.passArtifact,
 			preparedProgram);
 		glFlush();
 
@@ -154,5 +170,10 @@ void RuntimeShaderPrepareWorker::ThreadMain()
 std::string RuntimeShaderPrepareWorker::Fingerprint(const RuntimeShaderArtifact& artifact)
 {
 	const std::hash<std::string> hasher;
-	return artifact.shaderId + ":" + std::to_string(artifact.fragmentShaderSource.size()) + ":" + std::to_string(hasher(artifact.fragmentShaderSource));
+	std::string source;
+	for (const RuntimeShaderPassArtifact& pass : artifact.passes)
+		source += pass.passId + ":" + pass.outputName + ":" + pass.fragmentShaderSource + "\n";
+	if (source.empty())
+		source = artifact.fragmentShaderSource;
+	return artifact.shaderId + ":" + std::to_string(source.size()) + ":" + std::to_string(hasher(source));
 }

apps/RenderCadenceCompositor/render/runtime/RuntimeShaderPrepareWorker.h

@@ -35,8 +35,10 @@ private:
 	{
 		std::string layerId;
 		std::string shaderId;
+		std::string passId;
 		std::string sourceFingerprint;
 		RuntimeShaderArtifact artifact;
+		RuntimeShaderPassArtifact passArtifact;
 	};
 
 	void ThreadMain();

apps/RenderCadenceCompositor/render/runtime/RuntimeShaderProgram.h

@@ -4,13 +4,18 @@
 #include "../../runtime/RuntimeShaderArtifact.h"
 
 #include <string>
+#include <vector>
 
 struct RuntimePreparedShaderProgram
 {
 	std::string layerId;
 	std::string shaderId;
+	std::string passId;
 	std::string sourceFingerprint;
 	RuntimeShaderArtifact artifact;
+	RuntimeShaderPassArtifact passArtifact;
+	std::vector<std::string> inputNames;
+	std::string outputName;
 	GLuint program = 0;
 	GLuint vertexShader = 0;
 	GLuint fragmentShader = 0;

apps/RenderCadenceCompositor/render/runtime/RuntimeShaderRenderer.cpp

@@ -99,21 +99,41 @@ bool RuntimeShaderRenderer::BuildPreparedProgram(
 	const std::string& sourceFingerprint,
 	const RuntimeShaderArtifact& artifact,
 	RuntimePreparedShaderProgram& preparedProgram)
+{
+	RuntimeShaderPassArtifact passArtifact;
+	passArtifact.passId = "main";
+	passArtifact.fragmentShaderSource = artifact.fragmentShaderSource;
+	passArtifact.outputName = "layerOutput";
+	if (!artifact.passes.empty())
+		passArtifact = artifact.passes.front();
+	return BuildPreparedPassProgram(layerId, sourceFingerprint, artifact, passArtifact, preparedProgram);
+}
+
+bool RuntimeShaderRenderer::BuildPreparedPassProgram(
+	const std::string& layerId,
+	const std::string& sourceFingerprint,
+	const RuntimeShaderArtifact& artifact,
+	const RuntimeShaderPassArtifact& passArtifact,
+	RuntimePreparedShaderProgram& preparedProgram)
 {
 	preparedProgram = RuntimePreparedShaderProgram();
 	preparedProgram.layerId = layerId;
 	preparedProgram.shaderId = artifact.shaderId;
+	preparedProgram.passId = passArtifact.passId;
 	preparedProgram.sourceFingerprint = sourceFingerprint;
 	preparedProgram.artifact = artifact;
+	preparedProgram.passArtifact = passArtifact;
+	preparedProgram.inputNames = passArtifact.inputNames;
+	preparedProgram.outputName = passArtifact.outputName.empty() ? passArtifact.passId : passArtifact.outputName;
 
-	if (artifact.fragmentShaderSource.empty())
+	if (passArtifact.fragmentShaderSource.empty())
 	{
 		preparedProgram.error = "Cannot prepare an empty fragment shader.";
 		return false;
 	}
 
 	if (!BuildProgram(
-		artifact.fragmentShaderSource,
+		passArtifact.fragmentShaderSource,
 		preparedProgram.program,
 		preparedProgram.vertexShader,
 		preparedProgram.fragmentShader,

apps/RenderCadenceCompositor/render/runtime/RuntimeShaderRenderer.h

@@ -28,6 +28,12 @@ public:
 		const std::string& sourceFingerprint,
 		const RuntimeShaderArtifact& artifact,
 		RuntimePreparedShaderProgram& preparedProgram);
+	static bool BuildPreparedPassProgram(
+		const std::string& layerId,
+		const std::string& sourceFingerprint,
+		const RuntimeShaderArtifact& artifact,
+		const RuntimeShaderPassArtifact& passArtifact,
+		RuntimePreparedShaderProgram& preparedProgram);
 
 private:
 	bool EnsureStaticGlResources(std::string& error);

apps/RenderCadenceCompositor/runtime/RuntimeShaderArtifact.h

@@ -5,12 +5,21 @@
 #include <string>
 #include <vector>
 
+struct RuntimeShaderPassArtifact
+{
+	std::string passId;
+	std::string fragmentShaderSource;
+	std::vector<std::string> inputNames;
+	std::string outputName;
+};
+
 struct RuntimeShaderArtifact
 {
 	std::string layerId;
 	std::string shaderId;
 	std::string displayName;
 	std::string fragmentShaderSource;
+	std::vector<RuntimeShaderPassArtifact> passes;
 	std::string message;
 	std::vector<ShaderParameterDefinition> parameterDefinitions;
 };

apps/RenderCadenceCompositor/runtime/RuntimeSlangShaderCompiler.cpp

@@ -112,8 +112,6 @@ RuntimeSlangShaderBuild RuntimeSlangShaderCompiler::BuildShader(const std::strin
 			return build;
 		}
 
-		const ShaderPassDefinition& pass = shaderPackage.passes.front();
-
 		ShaderCompiler compiler(
 			repoRoot,
 			runtimeBuildDir / (shaderId + ".wrapper.slang"),
@@ -122,11 +120,22 @@ RuntimeSlangShaderBuild RuntimeSlangShaderCompiler::BuildShader(const std::strin
 			0);
 
 		const auto start = std::chrono::steady_clock::now();
-		if (!compiler.BuildPassFragmentShaderSource(shaderPackage, pass, build.artifact.fragmentShaderSource, error))
+		for (const ShaderPassDefinition& pass : shaderPackage.passes)
 		{
-			build.succeeded = false;
+			std::string fragmentShaderSource;
-			build.message = error.empty() ? "Slang compile failed." : error;
+			if (!compiler.BuildPassFragmentShaderSource(shaderPackage, pass, fragmentShaderSource, error))
-			return build;
+			{
+				build.succeeded = false;
+				build.message = error.empty() ? "Slang compile failed." : error;
+				return build;
+			}
+
+			RuntimeShaderPassArtifact passArtifact;
+			passArtifact.passId = pass.id;
+			passArtifact.fragmentShaderSource = std::move(fragmentShaderSource);
+			passArtifact.inputNames = pass.inputNames;
+			passArtifact.outputName = pass.outputName;
+			build.artifact.passes.push_back(std::move(passArtifact));
 		}
 
 		const auto end = std::chrono::steady_clock::now();
@@ -135,6 +144,8 @@ RuntimeSlangShaderBuild RuntimeSlangShaderCompiler::BuildShader(const std::strin
 		build.artifact.shaderId = shaderPackage.id;
 		build.artifact.displayName = shaderPackage.displayName;
 		build.artifact.parameterDefinitions = shaderPackage.parameters;
+		if (!build.artifact.passes.empty())
+			build.artifact.fragmentShaderSource = build.artifact.passes.front().fragmentShaderSource;
 		build.artifact.message = shaderPackage.displayName + " Slang compile completed in " + std::to_string(milliseconds) + " ms.";
 		build.message = build.artifact.message;
 		return build;

apps/RenderCadenceCompositor/runtime/SupportedShaderCatalog.cpp

@@ -9,8 +9,8 @@ namespace RenderCadenceCompositor
 {
 ShaderSupportResult CheckStatelessSinglePassShaderSupport(const ShaderPackage& shaderPackage)
 {
-	if (shaderPackage.passes.size() != 1)
+	if (shaderPackage.passes.empty())
-		return { false, "RenderCadenceCompositor currently supports only single-pass runtime shaders." };
+		return { false, "Shader package has no render passes." };
 
 	if (shaderPackage.temporal.enabled)
 		return { false, "RenderCadenceCompositor currently supports only stateless shaders; temporal history is not enabled in this app." };
@@ -30,6 +30,35 @@ ShaderSupportResult CheckStatelessSinglePassShaderSupport(const ShaderPackage& s
 			return { false, "RenderCadenceCompositor currently skips text parameters because they require per-shader text texture storage." };
 	}
 
+	bool writesLayerOutput = false;
+	for (const ShaderPassDefinition& pass : shaderPackage.passes)
+	{
+		if (pass.sourcePath.empty())
+		{
+			return { false, "Shader pass '" + pass.id + "' has no source." };
+		}
+		if (pass.outputName == "layerOutput")
+			writesLayerOutput = true;
+		for (const std::string& inputName : pass.inputNames)
+		{
+			if (inputName == "videoInput" || inputName == "layerInput")
+				continue;
+			bool matchesNamedOutput = false;
+			for (const ShaderPassDefinition& outputPass : shaderPackage.passes)
+			{
+				if (outputPass.outputName == inputName)
+				{
+					matchesNamedOutput = true;
+					break;
+				}
+			}
+			if (!matchesNamedOutput)
+				return { false, "Shader pass '" + pass.id + "' references unknown input '" + inputName + "'." };
+		}
+	}
+	if (!writesLayerOutput)
+		return { false, "Shader package must write a pass output named 'layerOutput'." };
+
 	return { true, std::string() };
 }
 

tests/RenderCadenceCompositorSupportedShaderCatalogTests.cpp

@@ -23,6 +23,8 @@ ShaderPackage MakeSinglePassPackage()
 	ShaderPassDefinition pass;
 	pass.id = "main";
 	pass.entryPoint = "mainImage";
+	pass.sourcePath = "shader.slang";
+	pass.outputName = "layerOutput";
 	shaderPackage.passes.push_back(pass);
 	return shaderPackage;
 }
@@ -37,19 +39,35 @@ void SupportsSinglePassStatelessPackage()
 	Expect(result.reason.empty(), "supported packages should not report a rejection reason");
 }
 
-void RejectsMultipassPackage()
+void SupportsStatelessNamedPassPackage()
 {
 	ShaderPackage shaderPackage = MakeSinglePassPackage();
+	shaderPackage.passes.front().outputName = "generatedMask";
 	ShaderPassDefinition secondPass;
 	secondPass.id = "second";
 	secondPass.entryPoint = "mainImage";
+	secondPass.sourcePath = "shader.slang";
+	secondPass.inputNames.push_back("generatedMask");
+	secondPass.outputName = "layerOutput";
 	shaderPackage.passes.push_back(secondPass);
 
 	const RenderCadenceCompositor::ShaderSupportResult result =
 		RenderCadenceCompositor::CheckStatelessSinglePassShaderSupport(shaderPackage);
 
-	Expect(!result.supported, "multipass packages should be rejected");
+	Expect(result.supported, "stateless named-pass packages should be supported");
-	Expect(result.reason.find("single-pass") != std::string::npos, "multipass rejection should explain the single-pass limit");
+	Expect(result.reason.empty(), "supported named-pass packages should not report a rejection reason");
+}
+
+void RejectsUnknownPassInput()
+{
+	ShaderPackage shaderPackage = MakeSinglePassPackage();
+	shaderPackage.passes.front().inputNames.push_back("missingIntermediate");
+
+	const RenderCadenceCompositor::ShaderSupportResult result =
+		RenderCadenceCompositor::CheckStatelessSinglePassShaderSupport(shaderPackage);
+
+	Expect(!result.supported, "packages with unknown pass inputs should be rejected");
+	Expect(result.reason.find("unknown input") != std::string::npos, "unknown input rejection should explain the missing named output");
 }
 
 void RejectsTemporalPackage()
@@ -97,7 +115,8 @@ void RejectsTextParameters()
 int main()
 {
 	SupportsSinglePassStatelessPackage();
-	RejectsMultipassPackage();
+	SupportsStatelessNamedPassPackage();
+	RejectsUnknownPassInput();
 	RejectsTemporalPackage();
 	RejectsTextureAssets();
 	RejectsTextParameters();