Support 32bit mesh indices

Editor/MeshToSDFEditor.cs

@@ -105,9 +105,6 @@ public class MeshToSDFEditor : Editor
         if (mesh.GetTopology(0) != MeshTopology.Triangles)
             EditorGUILayout.HelpBox("Only triangular topology meshes supported (MeshTopology.Triangles).", MessageType.Error);
 
-        if (mesh.indexFormat != UnityEngine.Rendering.IndexFormat.UInt16)
-            EditorGUILayout.HelpBox("Only 16 bit indices supported. The mesh is probably way too large.", MessageType.Error);
-
         if (mesh.GetIndexCount(0) > 3 * 10000)
             EditorGUILayout.HelpBox("This looks like a large mesh. For best performance and a smoother SDF, use a proxy mesh of under 10k triangles.", MessageType.Warning);
 

Runtime/MeshToSDF.compute

@@ -18,13 +18,21 @@ float _Offset;
 
 #define THREAD_GROUP_SIZE 64
 
+bool _IndexFormat16bit;
+
 uint GetIndex(ByteAddressBuffer indexBuffer, uint i)
 {
-	// 2 byte indices, Load() grabs 4 bytes at a time (4 byte aligned) so need to do some unpacking
-	uint entryIndex = i >> 1u;
-	uint entryOffset = i & 1u;
-	uint read = indexBuffer.Load(entryIndex << 2);
-	return entryOffset == 1u ? ((read >> 16) & 0xffff) : read & 0xffff;
+    if (_IndexFormat16bit)
+    {
+        // 2 byte indices, Load() grabs 4 bytes at a time (4 byte aligned) so need to do some unpacking
+        uint entryIndex = i >> 1u;
+        uint entryOffset = i & 1u;
+        uint read = indexBuffer.Load(entryIndex << 2);
+        return entryOffset == 1u ? ((read >> 16) & 0xffff) : read & 0xffff;
+    }
+    else
+        // 4 byte indices
+        return indexBuffer.Load(i << 2);
 }
 
 float _VertexBufferStride;

Runtime/MeshToSDF.cs

@@ -86,6 +86,7 @@ If you need signed distance or just need a limited shell around your surface, us
     GraphicsBuffer m_IndexBuffer = null;
     int m_VertexBufferStride;
     int m_VertexBufferPosAttributeOffset;
+    IndexFormat m_IndexFormat;
     CommandBuffer m_CommandBuffer = null;
 
     const int kThreadCount = 64;
@@ -112,6 +113,7 @@ If you need signed distance or just need a limited shell around your surface, us
         internal static int g_CellSize = Shader.PropertyToID("g_CellSize");
         internal static int g_VertexBuffer = Shader.PropertyToID("g_VertexBuffer");
         internal static int g_IndexBuffer = Shader.PropertyToID("g_IndexBuffer");
+        internal static int _IndexFormat16bit = Shader.PropertyToID("_IndexFormat16bit");
         internal static int _VertexBufferStride = Shader.PropertyToID("_VertexBufferStride");
         internal static int _VertexBufferPosAttributeOffset = Shader.PropertyToID("_VertexBufferPosAttributeOffset");
         internal static int _JumpOffset = Shader.PropertyToID("_JumpOffset");
@@ -278,6 +280,7 @@ If you need signed distance or just need a limited shell around your surface, us
         
         cmd.SetComputeBufferParam(m_Compute, kernel, Uniforms.g_VertexBuffer, m_VertexBuffer);
         cmd.SetComputeBufferParam(m_Compute, kernel, Uniforms.g_IndexBuffer, m_IndexBuffer);
+        cmd.SetComputeIntParam(m_Compute, Uniforms._IndexFormat16bit, m_IndexFormat == IndexFormat.UInt16 ? 1 : 0);
         cmd.SetComputeFloatParam(m_Compute, Uniforms._VertexBufferStride, m_VertexBufferStride);
         cmd.SetComputeFloatParam(m_Compute, Uniforms._VertexBufferPosAttributeOffset, m_VertexBufferPosAttributeOffset);
         
@@ -392,11 +395,6 @@ If you need signed distance or just need a limited shell around your surface, us
             Debug.LogError("MeshToSDF needs a mesh with triangle topology.", this);
             return false;
         }
-        if (mesh.indexFormat != IndexFormat.UInt16)
-        {
-            Debug.LogError("MeshToSDF needs a mesh with 16 bit index format (mesh probably too big).", this);
-            return false;
-        }
 
         int stream = mesh.GetVertexAttributeStream(VertexAttribute.Position);
         if (stream < 0)
@@ -405,6 +403,7 @@ If you need signed distance or just need a limited shell around your surface, us
             return false;
         }
 
+        m_IndexFormat = mesh.indexFormat;
         m_VertexBufferStride = mesh.GetVertexBufferStride(stream);
         m_VertexBufferPosAttributeOffset = mesh.GetVertexAttributeOffset(VertexAttribute.Position);
         m_VertexBuffer = m_SkinnedMeshRenderer != null ? m_SkinnedMeshRenderer.GetVertexBuffer() : mesh.GetVertexBuffer(stream);