[Vulkan] Fix conservative raster validation error

VK_EXT_conservative_rasterization must be enabled for conservative
rasterization to work properly. Likewise, the pNext chain of
VkPipelineRasterizationStateCreateInfo should not contain a
struct of that extension if it is not used.

src/Aardvark.Rendering.Vulkan/Core/Platform.fs

@@ -38,6 +38,8 @@ module Instance =
         let ShaderSubgroupVote              = EXTShaderSubgroupVote.Name
         let ShaderSubgroupBallot            = EXTShaderSubgroupBallot.Name
 
+        let ConservativeRasterization       = EXTConservativeRasterization.Name
+
         let Debug = [
             EXTDebugReport.Name
             EXTDebugUtils.Name

src/Aardvark.Rendering.Vulkan/Management/ResourceManager.fs

@@ -966,7 +966,8 @@ module Resources =
         inherit AbstractPointerResourceWithEquality<VkPipelineRasterizationStateCreateInfo>(owner, key)
 
         override x.Free(info : VkPipelineRasterizationStateCreateInfo) =
-            Marshal.FreeHGlobal info.pNext
+            if info.pNext <> 0n then
+                Marshal.FreeHGlobal info.pNext
 
         override x.Compute(user, token, renderToken) =
             let depthClamp = depthClamp.GetValue(user, token, renderToken)
@@ -977,18 +978,23 @@ module Resources =
             let conservativeRaster = conservativeRaster.GetValue(user, token, renderToken)
             let state = RasterizerState.create conservativeRaster depthClamp bias cull front fill
 
-            let conservativeRaster =
-                VkPipelineRasterizationConservativeStateCreateInfoEXT(
-                    VkPipelineRasterizationConservativeStateCreateFlagsEXT.None,
-                    (if conservativeRaster then VkConservativeRasterizationModeEXT.Overestimate else VkConservativeRasterizationModeEXT.Disabled),
-                    0.0f
-                )
+            let pConservativeRaster =
+                if conservativeRaster then
+                    let info =
+                        VkPipelineRasterizationConservativeStateCreateInfoEXT(
+                            VkPipelineRasterizationConservativeStateCreateFlagsEXT.None,
+                            VkConservativeRasterizationModeEXT.Overestimate,
+                            0.0f
+                        )
 
-            let pConservativeRaster = NativePtr.alloc<VkPipelineRasterizationConservativeStateCreateInfoEXT> 1
-            conservativeRaster |> NativePtr.write pConservativeRaster
+                    let ptr = NativePtr.alloc<VkPipelineRasterizationConservativeStateCreateInfoEXT> 1
+                    info |> NativePtr.write ptr
+                    NativePtr.toNativeInt ptr
+                else
+                    0n
 
             VkPipelineRasterizationStateCreateInfo(
-                NativePtr.toNativeInt pConservativeRaster,
+                pConservativeRaster,
                 VkPipelineRasterizationStateCreateFlags.None,
                 (if state.depthClampEnable then 1u else 0u),
                 (if state.rasterizerDiscardEnable then 1u else 0u),

src/Aardvark.Rendering.Vulkan/Runtime/Headless.fs

@@ -14,6 +14,7 @@ type HeadlessVulkanApplication(debug : IDebugConfig, instanceExtensions : list<s
             yield Instance.Extensions.ShaderSubgroupVote
             yield Instance.Extensions.ShaderSubgroupBallot
             yield Instance.Extensions.GetPhysicalDeviceProperties2
+            yield Instance.Extensions.ConservativeRasterization
 
             yield! Instance.Extensions.Raytracing
             yield! Instance.Extensions.Sharing

src/Aardvark.SceneGraph/Pools/ManagedTracePool.fs

@@ -772,7 +772,7 @@ and ManagedTracePool(runtime : IRuntime, signature : TraceObjectSignature,
     member x.GetVertexAttribute(semantic : Symbol) =
         match x.TryGetVertexAttribute semantic with
         | Some attr -> attr
-        | None _ -> failf "could not find vertex attribute '%A'" semantic
+        | None -> failf "could not find vertex attribute '%A'" semantic
 
     member x.TryGetFaceAttribute(semantic : Symbol) =
         faceAttributeBuffers |> Map.tryFind semantic
@@ -781,7 +781,7 @@ and ManagedTracePool(runtime : IRuntime, signature : TraceObjectSignature,
     member x.GetFaceAttribute(semantic : Symbol) =
         match x.TryGetFaceAttribute semantic with
         | Some attr -> attr
-        | None _ -> failf "could not find face attribute '%A'" semantic
+        | None -> failf "could not find face attribute '%A'" semantic
 
     member x.TryGetGeometryAttribute(semantic : Symbol) =
         geometryAttributeBuffers |> Map.tryFind semantic
@@ -790,7 +790,7 @@ and ManagedTracePool(runtime : IRuntime, signature : TraceObjectSignature,
     member x.GetGeometryAttribute(semantic : Symbol) =
         match x.TryGetGeometryAttribute semantic with
         | Some attr -> attr
-        | None _ -> failf "could not find geometry attribute '%A'" semantic
+        | None -> failf "could not find geometry attribute '%A'" semantic
 
     member x.TryGetInstanceAttribute(semantic : Symbol) =
         instanceAttributeBuffers |> Map.tryFind semantic
@@ -799,7 +799,7 @@ and ManagedTracePool(runtime : IRuntime, signature : TraceObjectSignature,
     member x.GetInstanceAttribute(semantic : Symbol) =
         match x.TryGetInstanceAttribute semantic with
         | Some attr -> attr
-        | None _ -> failf "could not find instance attribute '%A'" semantic
+        | None -> failf "could not find instance attribute '%A'" semantic
 
     member x.Dispose() =
         lock x (fun _ ->

src/Application/Aardvark.Application.WinForms.Vulkan/Application.fs

@@ -102,6 +102,7 @@ type VulkanApplication(debug : IDebugConfig, chooseDevice : list<PhysicalDevice>
             yield Instance.Extensions.ShaderSubgroupVote
             yield Instance.Extensions.ShaderSubgroupBallot
             yield Instance.Extensions.GetPhysicalDeviceProperties2
+            yield Instance.Extensions.ConservativeRasterization
 
             yield! Instance.Extensions.Raytracing
             yield! Instance.Extensions.Sharing