[dxvk] Improve behaviour when variableMultisampleRate is not supported

src/dxvk/dxvk_adapter.cpp

@@ -349,6 +349,13 @@ namespace dxvk {
     extensionsEnabled.merge(m_extraExtensions);
     DxvkNameList extensionNameList = extensionsEnabled.toNameList();
 
+    // Always enable robust buffer access
+    enabledFeatures.core.features.robustBufferAccess = VK_TRUE;
+
+    // Enable variable multisample rate if supported
+    enabledFeatures.core.features.variableMultisampleRate =
+      m_deviceFeatures.core.features.variableMultisampleRate;
+
     // Optionally used by some client API extensions
     enabledFeatures.vk12.drawIndirectCount =
       m_deviceFeatures.vk12.drawIndirectCount;

src/dxvk/dxvk_context.cpp

@@ -54,6 +54,13 @@ namespace dxvk {
     // that we don't have to scan device features at draw time
     if (m_device->mustTrackPipelineLifetime())
       m_features.set(DxvkContextFeature::TrackGraphicsPipeline);
+
+    // Variable multisample rate is needed to efficiently support
+    // rendering without bound render targets, otherwise we may
+    // have to interrupt the current render pass whenever the
+    // requested rasterizer sample count changes
+    if (m_device->features().core.features.variableMultisampleRate)
+      m_features.set(DxvkContextFeature::VariableMultisampleRate);
   }
   
   
@@ -2458,6 +2465,11 @@ namespace dxvk {
       m_flags.set(DxvkContextFlag::GpDirtyRasterizerState);
     }
 
+    if (unlikely(!m_features.test(DxvkContextFeature::VariableMultisampleRate))) {
+      if (rs.sampleCount != m_state.gp.state.rs.sampleCount())
+        m_flags.set(DxvkContextFlag::GpDirtyFramebuffer);
+    }
+
     DxvkRsInfo rsInfo(
       rs.depthClipEnable,
       rs.depthBiasEnable,

src/dxvk/dxvk_context_state.h

@@ -62,6 +62,7 @@ namespace dxvk {
    */
   enum class DxvkContextFeature : uint32_t {
     TrackGraphicsPipeline,
+    VariableMultisampleRate,
     FeatureCount
   };