From 48a03ae21ffc8ab03dcccfd2c2ef45923e2cd322 Mon Sep 17 00:00:00 2001
From: baldurk <baldurk@baldurk.org>
Date: Fri, 27 Nov 2015 20:42:42 +0100
Subject: [PATCH] Only fetch the PostVS data needed for this draw, not the
 whole buffer

* For instanced draws where there are many instance and each instance is
  a lot, this saves fetching a *ton* of redundant data.
---
 renderdocui/Windows/BufferViewer.cs | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/renderdocui/Windows/BufferViewer.cs b/renderdocui/Windows/BufferViewer.cs
index 05395bb5c..cb2da4664 100644
--- a/renderdocui/Windows/BufferViewer.cs
+++ b/renderdocui/Windows/BufferViewer.cs
@@ -967,8 +967,6 @@ namespace renderdocui.Windows
                 }
                 else
                 {
-                    ret.Buffers[0] = r.GetBufferData(ret.PostVS.buf, ret.PostVS.offset, 0);
-
                     ret.Topology = ret.PostVS.topo;
 
                     ret.IndexCount = ret.PostVS.numVerts;
@@ -982,6 +980,8 @@ namespace renderdocui.Windows
                 ret.Indices = null;
                 ret.DataIndices = null;
 
+                uint maxIndex = Math.Max(ret.IndexCount, 1) - 1;
+
                 if (ret.PostVS.buf != ResourceId.Null && type == MeshDataStage.VSOut &&
                     (input.Drawcall.flags & DrawcallFlags.UseIBuffer) > 0 && input.IndexBuffer != ResourceId.Null)
                 {
@@ -1052,8 +1052,20 @@ namespace renderdocui.Windows
                             Buffer.BlockCopy(rawidxs, 0, ret.DataIndices, 0, ret.DataIndices.Length * sizeof(uint));
                         }
                     }
+
+                    maxIndex = 0;
+                    foreach (var i in ret.DataIndices)
+                    {
+                        if (i == input.IndexRestartValue && input.IndexRestart)
+                            continue;
+
+                        maxIndex = Math.Max(maxIndex, i);
+                    }
                 }
 
+                if (ret.PostVS.buf != ResourceId.Null)
+                    ret.Buffers[0] = r.GetBufferData(ret.PostVS.buf, ret.PostVS.offset, (maxIndex + 1) * ret.PostVS.stride);
+
                 return ret;
             }
             else if (input.Buffers != null && m_Output != null)