Add support for DX12 and Vulkan drawIndexedIndirectCount

Author: yohjimane

include/nvrhi/nvrhi.h

@@ -2665,6 +2665,9 @@ namespace nvrhi
 
         IBuffer* indirectParams = nullptr;
 
+        IBuffer* indirectCountBuffer = nullptr;
+        uint32_t indirectCountOffset = 0;
+
         GraphicsState& setPipeline(IGraphicsPipeline* value) { pipeline = value; return *this; }
         GraphicsState& setFramebuffer(IFramebuffer* value) { framebuffer = value; return *this; }
         GraphicsState& setViewport(const ViewportState& value) { viewport = value; return *this; }
@@ -2675,6 +2678,7 @@ namespace nvrhi
         GraphicsState& addVertexBuffer(const VertexBufferBinding& value) { vertexBuffers.push_back(value); return *this; }
         GraphicsState& setIndexBuffer(const IndexBufferBinding& value) { indexBuffer = value; return *this; }
         GraphicsState& setIndirectParams(IBuffer* value) { indirectParams = value; return *this; }
+        GraphicsState& setIndirectCountBuffer(IBuffer* buf, uint32_t offset = 0) { indirectCountBuffer = buf; indirectCountOffset = offset; return *this; }
     };
 
     struct DrawArguments
@@ -3286,7 +3290,14 @@ namespace nvrhi
         // - DX12: Maps to ExecuteIndirect with a predefined signature.
         // - Vulkan: Maps to vkCmdDrawIndexedIndirect.
         virtual void drawIndexedIndirect(uint32_t offsetBytes, uint32_t drawCount = 1) = 0;
-        
+
+		// Draws primitives with indexed vertices using the parameters provided in the indirect arguments buffer.
+		// The draw count is read from the indirectCountBuffer specified in setGraphicsState(...).
+		// - DX11: Not supported (falls back to maxDrawCount draws).
+		// - DX12: Maps to ExecuteIndirect with pCountBuffer parameter.
+		// - Vulkan: Maps to vkCmdDrawIndexedIndirectCount.
+		virtual void drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount) = 0;
+
         // Sets the specified compute state on the command list.
         // The state includes the pipeline (or individual shaders on DX11) and all resources bound to it.
         // See the members of ComputeState for more information.

src/d3d11/d3d11-backend.h

@@ -323,6 +323,7 @@ namespace nvrhi::d3d11
         void drawIndexed(const DrawArguments& args) override;
         void drawIndirect(uint32_t offsetBytes, uint32_t drawCount) override;
         void drawIndexedIndirect(uint32_t offsetBytes, uint32_t drawCount) override;
+        void drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount) override;
 
         void setComputeState(const ComputeState& state) override;
         void dispatch(uint32_t groupsX, uint32_t groupsY = 1, uint32_t groupsZ = 1) override;

src/d3d11/d3d11-graphics.cpp

@@ -414,6 +414,12 @@ namespace nvrhi::d3d11
         }
     }
 
+    void CommandList::drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount)
+    {
+        // D3D11 doesn't support count buffers - fall back to default drawIndexedIndirect behavior
+        drawIndexedIndirect(offsetBytes, maxDrawCount);
+    }
+
     ID3D11BlendState* Device::getBlendState(const BlendState& blendState)
     {
         size_t hash = 0;

src/d3d12/d3d12-backend.h

@@ -979,6 +979,7 @@ namespace nvrhi::d3d12
         void drawIndexed(const DrawArguments& args) override;
         void drawIndirect(uint32_t offsetBytes, uint32_t drawCount) override;
         void drawIndexedIndirect(uint32_t offsetBytes, uint32_t drawCount) override;
+        void drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount) override;
 
         void setComputeState(const ComputeState& state) override;
         void dispatch(uint32_t groupsX, uint32_t groupsY = 1, uint32_t groupsZ = 1) override;

src/d3d12/d3d12-graphics.cpp

@@ -580,7 +580,26 @@ namespace nvrhi::d3d12
 
         m_ActiveCommandList->commandList->ExecuteIndirect(m_Context.drawIndexedIndirectSignature, drawCount, indirectParams->resource, offsetBytes, nullptr, 0);
     }
-    
+
+    void CommandList::drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount)
+    {
+        Buffer* indirectParams = checked_cast<Buffer*>(m_CurrentGraphicsState.indirectParams);
+        Buffer* countBuf = checked_cast<Buffer*>(m_CurrentGraphicsState.indirectCountBuffer);
+        assert(indirectParams);
+        assert(countBuf);
+
+        updateGraphicsVolatileBuffers();
+
+        m_ActiveCommandList->commandList->ExecuteIndirect(
+            m_Context.drawIndexedIndirectSignature,
+            maxDrawCount,
+            indirectParams->resource,
+            offsetBytes,
+            countBuf->resource,
+            m_CurrentGraphicsState.indirectCountOffset
+        );
+    }
+
     DX12_ViewportState convertViewportState(const RasterState& rasterState, const FramebufferInfoEx& framebufferInfo, const ViewportState& vpState)
     {
         DX12_ViewportState ret;

src/validation/validation-backend.h

@@ -223,6 +223,7 @@ namespace nvrhi::validation
         void drawIndexed(const DrawArguments& args) override;
         void drawIndirect(uint32_t offsetBytes, uint32_t drawCount) override;
         void drawIndexedIndirect(uint32_t offsetBytes, uint32_t drawCount) override;
+        void drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount) override;
 
         void setComputeState(const ComputeState& state) override;
         void dispatch(uint32_t groupsX, uint32_t groupsY = 1, uint32_t groupsZ = 1) override;

src/validation/validation-commandlist.cpp

@@ -762,6 +762,39 @@ namespace nvrhi::validation
         m_CommandList->drawIndexedIndirect(offsetBytes, drawCount);
     }
 
+    void CommandListWrapper::drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount)
+    {
+        if (!requireOpenState())
+            return;
+
+        if (!requireType(CommandQueue::Graphics, "drawIndexedIndirectCount"))
+            return;
+
+        if (!m_GraphicsStateSet)
+        {
+            error("Graphics state is not set before a drawIndexedIndirectCount call.\n"
+                "Note that setting compute state invalidates the graphics state.");
+            return;
+        }
+
+        if (!m_CurrentGraphicsState.indirectParams)
+        {
+            error("Indirect params buffer is not set before a drawIndexedIndirectCount call.");
+            return;
+        }
+
+        if (!m_CurrentGraphicsState.indirectCountBuffer)
+        {
+            error("Indirect count buffer is not set before a drawIndexedIndirectCount call.");
+            return;
+        }
+
+        if (!validatePushConstants("graphics", "setGraphicsState"))
+            return;
+
+        m_CommandList->drawIndexedIndirectCount(offsetBytes, maxDrawCount);
+    }
+
     void CommandListWrapper::setComputeState(const ComputeState& state)
     {
         if (!requireOpenState())

src/vulkan/vulkan-backend.h

@@ -1239,6 +1239,7 @@ namespace nvrhi::vulkan
         void drawIndexed(const DrawArguments& args) override;
         void drawIndirect(uint32_t offsetBytes, uint32_t drawCount) override;
         void drawIndexedIndirect(uint32_t offsetBytes, uint32_t drawCount) override;
+        void drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount) override;
 
         void setComputeState(const ComputeState& state) override;
         void dispatch(uint32_t groupsX, uint32_t groupsY = 1, uint32_t groupsZ = 1) override;

src/vulkan/vulkan-graphics.cpp

@@ -713,4 +713,25 @@ namespace nvrhi::vulkan
         m_CurrentCmdBuf->cmdBuf.drawIndexedIndirect(indirectParams->buffer, offsetBytes, drawCount, sizeof(DrawIndexedIndirectArguments));
     }
 
+    void CommandList::drawIndexedIndirectCount(uint32_t offsetBytes, uint32_t maxDrawCount)
+    {
+        assert(m_CurrentCmdBuf);
+
+        updateGraphicsVolatileBuffers();
+
+        Buffer* indirectParams = checked_cast<Buffer*>(m_CurrentGraphicsState.indirectParams);
+        Buffer* countBuf = checked_cast<Buffer*>(m_CurrentGraphicsState.indirectCountBuffer);
+        assert(indirectParams);
+        assert(countBuf);
+
+        m_CurrentCmdBuf->cmdBuf.drawIndexedIndirectCount(
+            indirectParams->buffer,
+            offsetBytes,
+            countBuf->buffer,
+            m_CurrentGraphicsState.indirectCountOffset,
+            maxDrawCount,
+            sizeof(DrawIndexedIndirectArguments)
+        );
+    }
+
 } // namespace nvrhi::vulkan