[dxvk] Bind dummy resource for unbound vertex and index buffers

Allows GTA V to run, although heavy rendering artifacts remain.

src/dxvk/dxvk_context.cpp

@@ -1185,8 +1185,12 @@ namespace dxvk {
       m_flags.clr(DxvkContextFlag::GpDirtyPipelineState);
       
       for (uint32_t i = 0; i < m_state.gp.state.ilBindingCount; i++) {
+        const uint32_t binding = m_state.gp.state.ilBindings[i].binding;
+        
         m_state.gp.state.ilBindings[i].stride
-          = m_state.vi.vertexStrides[m_state.gp.state.ilBindings[i].binding];
+          = (m_state.vi.bindingMask & (1u << binding)) != 0
+            ? m_state.vi.vertexStrides[binding]
+            : 0;
       }
       
       for (uint32_t i = m_state.gp.state.ilBindingCount; i < MaxNumVertexBindings; i++)
@@ -1399,6 +1403,10 @@ namespace dxvk {
           m_state.vi.indexType);
         m_cmd->trackResource(
           physicalSlice.resource());
+      } else {
+        m_cmd->cmdBindIndexBuffer(
+          m_device->dummyBufferHandle(),
+          0, VK_INDEX_TYPE_UINT32);
       }
     }
   }
@@ -1408,6 +1416,8 @@ namespace dxvk {
     if (m_flags.test(DxvkContextFlag::GpDirtyVertexBuffers)) {
       m_flags.clr(DxvkContextFlag::GpDirtyVertexBuffers);
       
+      uint32_t bindingMask = 0;
+      
       for (uint32_t i = 0; i < m_state.gp.state.ilBindingCount; i++) {
         const uint32_t binding = m_state.gp.state.ilBindings[i].binding;
         
@@ -1419,8 +1429,20 @@ namespace dxvk {
           
           m_cmd->cmdBindVertexBuffers(binding, 1, &handle, &offset);
           m_cmd->trackResource(vbo.resource());
+          
+          bindingMask |= 1u << binding;
+        } else {
+          const VkBuffer     handle = m_device->dummyBufferHandle();
+          const VkDeviceSize offset = 0;
+          
+          m_cmd->cmdBindVertexBuffers(binding, 1, &handle, &offset);
         }
       }
+      
+      if (m_state.vi.bindingMask != bindingMask) {
+        m_flags.set(DxvkContextFlag::GpDirtyPipelineState);
+        m_state.vi.bindingMask = bindingMask;
+      }
     }
   }
   

src/dxvk/dxvk_context_state.h

@@ -38,7 +38,8 @@ namespace dxvk {
   
   struct DxvkVertexInputState {
     DxvkBufferSlice indexBuffer;
-    VkIndexType     indexType = VK_INDEX_TYPE_UINT32;
+    VkIndexType     indexType   = VK_INDEX_TYPE_UINT32;
+    uint32_t        bindingMask = 0;
     
     std::array<DxvkBufferSlice,
       DxvkLimits::MaxNumVertexBindings> vertexBuffers;

src/dxvk/dxvk_device.h

@@ -275,6 +275,14 @@ namespace dxvk {
       const Rc<DxvkSurface>&          surface,
       const DxvkSwapchainProperties&  properties);
     
+    /**
+     * \brief Dummy buffer handle
+     * \returns Use for unbound vertex buffers.
+     */
+    VkBuffer dummyBufferHandle() const {
+      return m_unboundResources.bufferHandle();
+    }
+    
     /**
      * \brief Dummy buffer descriptor
      * \returns Descriptor that points to a dummy buffer

src/dxvk/dxvk_unbound.h

@@ -20,10 +20,22 @@ namespace dxvk {
     DxvkUnboundResources(DxvkDevice* dev);
     ~DxvkUnboundResources();
     
+    /**
+     * \brief Dummy buffer handle
+     * 
+     * Returns a handle to a buffer filled
+     * with zeroes. Use for unbound vertex
+     * and index buffers.
+     * \returns Dummy buffer handle
+     */
+    VkBuffer bufferHandle() const {
+      return m_buffer->slice().handle();
+    }
+    
     /**
      * \brief Dummy buffer descriptor
      * 
-     * Points to a tiny buffer with undefined
+     * Points to a small buffer with undefined
      * values. Do not access this buffer.
      * \returns Dummy buffer descriptor
      */