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Source/Engine/Tools/ModelTool/VertexTriangleAdjacency.h

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+// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.
+
+#pragma once
+
+#if COMPILE_WITH_MODEL_TOOL
+
+#include "Engine/Core/Config.h"
+#include "Engine/Core/Types/BaseTypes.h"
+#include "Engine/Platform/Platform.h"
+
+/// <summary>
+/// The VertexTriangleAdjacency class computes a vertex-triangle adjacency map from a given index buffer.
+/// </summary>
+class VertexTriangleAdjacency
+{
+public:
+
+    /// <summary>
+    /// Construction from an existing index buffer
+    /// </summary>
+    /// <param name="indices">The index buffer.</param>
+    /// <param name="indicesCount">The number of triangles in the buffer.</param>
+    /// <param name="vertexCount">The number of referenced vertices. This value is computed automatically if 0 is specified.</param>
+    /// <param name="computeNumTriangles">If you want the class to compute a list containing the number of referenced triangles per vertex per vertex - pass true.</param>
+    VertexTriangleAdjacency(uint32* indices, int32 indicesCount, uint32 vertexCount = 0, bool computeNumTriangles = true);
+
+    /// <summary>
+    /// Destructor
+    /// </summary>
+    ~VertexTriangleAdjacency();
+
+public:
+
+    /// <summary>
+    /// The offset table
+    /// </summary>
+    uint32* OffsetTable;
+
+    /// <summary>
+    /// The adjacency table.
+    /// </summary>
+    uint32* AdjacencyTable;
+
+    /// <summary>
+    /// The table containing the number of referenced triangles per vertex.
+    /// </summary>
+    uint32* LiveTriangles;
+
+    /// <summary>
+    /// The total number of referenced vertices.
+    /// </summary>
+    uint32 NumVertices;
+
+public:
+
+    /// <summary>
+    /// Gets all triangles adjacent to a vertex.
+    /// </summary>
+    /// <param name="vertexIndex">The index of the vertex.</param>
+    /// <returns>A pointer to the adjacency list.</returns>
+    uint32* GetAdjacentTriangles(uint32 vertexIndex) const
+    {
+        ASSERT(vertexIndex >= 0 && vertexIndex < NumVertices);
+        return &AdjacencyTable[OffsetTable[vertexIndex]];
+    }
+
+    /// <summary>
+    /// Gets the number of triangles that are referenced by a vertex. This function returns a reference that can be modified.
+    /// </summary>
+    /// <param name="vertexIndex">The index of the vertex.</param>
+    /// <returns>The number of referenced triangles</returns>
+    uint32& GetNumTrianglesPtr(uint32 vertexIndex) const
+    {
+        ASSERT(vertexIndex >= 0 && vertexIndex < NumVertices);
+        ASSERT(nullptr != LiveTriangles);
+        return LiveTriangles[vertexIndex];
+    }
+};
+
+#endif