From 722191184b92160bbdb2e4114c7f6930963fe55d Mon Sep 17 00:00:00 2001
From: baldurk <baldurk@baldurk.org>
Date: Thu, 8 Jun 2023 17:02:46 +0100
Subject: [PATCH] Handle degenerate case on D3D12 of indexed draw with no index
 buffer

---
 renderdoc/driver/d3d12/d3d12_postvs.cpp     |  5 ++
 renderdoc/driver/d3d12/d3d12_rendermesh.cpp | 51 +++++++++++++--------
 renderdoc/driver/d3d12/d3d12_replay.cpp     |  9 +++-
 3 files changed, 46 insertions(+), 19 deletions(-)

diff --git a/renderdoc/driver/d3d12/d3d12_postvs.cpp b/renderdoc/driver/d3d12/d3d12_postvs.cpp
index f33e55b7e..a7b115fd8 100644
--- a/renderdoc/driver/d3d12/d3d12_postvs.cpp
+++ b/renderdoc/driver/d3d12/d3d12_postvs.cpp
@@ -1495,6 +1495,11 @@ MeshFormat D3D12Replay::GetPostVSBuffers(uint32_t eventId, uint32_t instID, uint
     ret.indexByteStride = s.idxFmt == DXGI_FORMAT_R16_UINT ? 2 : 4;
     ret.indexByteSize = ~0ULL;
   }
+  else if(s.useIndices)
+  {
+    // indicate that an index buffer is still needed
+    ret.indexByteStride = 4;
+  }
   else
   {
     ret.indexResourceId = ResourceId();
diff --git a/renderdoc/driver/d3d12/d3d12_rendermesh.cpp b/renderdoc/driver/d3d12/d3d12_rendermesh.cpp
index 6a7da81b8..5c2f77cf6 100644
--- a/renderdoc/driver/d3d12/d3d12_rendermesh.cpp
+++ b/renderdoc/driver/d3d12/d3d12_rendermesh.cpp
@@ -358,19 +358,23 @@ void D3D12Replay::RenderMesh(uint32_t eventId, const rdcarray<MeshFormat> &secon
 
         if(fmt.indexByteStride)
         {
-          if(fmt.indexResourceId != ResourceId())
-          {
-            ID3D12Resource *ib =
-                m_pDevice->GetResourceManager()->GetCurrentAs<ID3D12Resource>(fmt.indexResourceId);
+          ID3D12Resource *ib =
+              m_pDevice->GetResourceManager()->GetCurrentAs<ID3D12Resource>(fmt.indexResourceId);
 
+          if(ib)
+          {
             D3D12_INDEX_BUFFER_VIEW iview;
             iview.BufferLocation = ib->GetGPUVirtualAddress() + fmt.indexByteOffset;
             iview.SizeInBytes = (UINT)fmt.indexByteSize;
             iview.Format = fmt.indexByteStride == 2 ? DXGI_FORMAT_R16_UINT : DXGI_FORMAT_R32_UINT;
             list->IASetIndexBuffer(&iview);
-
-            list->DrawIndexedInstanced(fmt.numIndices, 1, 0, fmt.baseVertex, 0);
           }
+          else
+          {
+            list->IASetIndexBuffer(NULL);
+          }
+
+          list->DrawIndexedInstanced(fmt.numIndices, 1, 0, fmt.baseVertex, 0);
         }
         else
         {
@@ -486,19 +490,23 @@ void D3D12Replay::RenderMesh(uint32_t eventId, const rdcarray<MeshFormat> &secon
 
     if(cfg.position.indexByteStride)
     {
-      if(cfg.position.indexResourceId != ResourceId())
-      {
-        ID3D12Resource *ib = m_pDevice->GetResourceManager()->GetCurrentAs<ID3D12Resource>(
-            cfg.position.indexResourceId);
+      ID3D12Resource *ib =
+          m_pDevice->GetResourceManager()->GetCurrentAs<ID3D12Resource>(cfg.position.indexResourceId);
 
+      if(ib)
+      {
         D3D12_INDEX_BUFFER_VIEW view;
         view.BufferLocation = ib->GetGPUVirtualAddress() + cfg.position.indexByteOffset;
         view.SizeInBytes = (UINT)cfg.position.indexByteSize;
         view.Format = cfg.position.indexByteStride == 2 ? DXGI_FORMAT_R16_UINT : DXGI_FORMAT_R32_UINT;
         list->IASetIndexBuffer(&view);
-
-        list->DrawIndexedInstanced(cfg.position.numIndices, 1, 0, cfg.position.baseVertex, 0);
       }
+      else
+      {
+        list->IASetIndexBuffer(NULL);
+      }
+
+      list->DrawIndexedInstanced(cfg.position.numIndices, 1, 0, cfg.position.baseVertex, 0);
     }
     else
     {
@@ -529,16 +537,23 @@ void D3D12Replay::RenderMesh(uint32_t eventId, const rdcarray<MeshFormat> &secon
 
     list->SetGraphicsRoot32BitConstants(2, 4, &pixelData, 0);
 
-    if(cfg.position.indexByteStride && cfg.position.indexResourceId != ResourceId())
+    if(cfg.position.indexByteStride)
     {
       ID3D12Resource *ib =
           m_pDevice->GetResourceManager()->GetCurrentAs<ID3D12Resource>(cfg.position.indexResourceId);
 
-      D3D12_INDEX_BUFFER_VIEW view;
-      view.BufferLocation = ib->GetGPUVirtualAddress() + cfg.position.indexByteOffset;
-      view.SizeInBytes = (UINT)cfg.position.indexByteSize;
-      view.Format = cfg.position.indexByteStride == 2 ? DXGI_FORMAT_R16_UINT : DXGI_FORMAT_R32_UINT;
-      list->IASetIndexBuffer(&view);
+      if(ib)
+      {
+        D3D12_INDEX_BUFFER_VIEW view;
+        view.BufferLocation = ib->GetGPUVirtualAddress() + cfg.position.indexByteOffset;
+        view.SizeInBytes = (UINT)cfg.position.indexByteSize;
+        view.Format = cfg.position.indexByteStride == 2 ? DXGI_FORMAT_R16_UINT : DXGI_FORMAT_R32_UINT;
+        list->IASetIndexBuffer(&view);
+      }
+      else
+      {
+        list->IASetIndexBuffer(NULL);
+      }
 
       list->DrawIndexedInstanced(cfg.position.numIndices, 1, 0, cfg.position.baseVertex, 0);
     }
diff --git a/renderdoc/driver/d3d12/d3d12_replay.cpp b/renderdoc/driver/d3d12/d3d12_replay.cpp
index 148efc0d7..733385b50 100644
--- a/renderdoc/driver/d3d12/d3d12_replay.cpp
+++ b/renderdoc/driver/d3d12/d3d12_replay.cpp
@@ -2138,7 +2138,7 @@ uint32_t D3D12Replay::PickVertex(uint32_t eventId, int32_t width, int32_t height
 
   cbuf.PickCoords = Vec2f((float)x, (float)y);
   cbuf.PickViewport = Vec2f((float)width, (float)height);
-  cbuf.PickIdx = cfg.position.indexByteStride ? 1 : 0;
+  cbuf.PickIdx = cfg.position.indexByteStride && cfg.position.indexResourceId != ResourceId() ? 1 : 0;
   cbuf.PickNumVerts = cfg.position.numIndices;
   cbuf.PickUnproject = cfg.position.unproject ? 1 : 0;
   cbuf.PickFlipY = cfg.position.flipY;
@@ -2489,6 +2489,13 @@ uint32_t D3D12Replay::PickVertex(uint32_t eventId, int32_t width, int32_t height
   }
   else
   {
+    if(cfg.position.indexByteStride)
+    {
+      maxIndex = 0;
+      if(cfg.position.baseVertex > 0)
+        minIndex = maxIndex = (uint32_t)cfg.position.baseVertex;
+    }
+
     sdesc.Buffer.NumElements = 4;
     m_pDevice->CreateShaderResourceView(NULL, &sdesc, GetDebugManager()->GetCPUHandle(PICK_IB_SRV));
   }