MyMesh: split off IndexBuffer conversion from trianglesToLines()

stephengold · Apr 23, 2024 · 7e11b4f · 7e11b4f
1 parent 557e401
commit 7e11b4f
Showing 1 changed file with 40 additions and 17 deletions.
diff --git a/HeartLibrary/src/main/java/jme3utilities/MyMesh.java b/HeartLibrary/src/main/java/jme3utilities/MyMesh.java
@@ -1501,20 +1501,24 @@ public static void translate(Mesh mesh, Vector3f offset) {
     }
 
     /**
-     * Convert mesh triangles to lines.
+     * Convert IndexBuffer triangles to lines.
      *
-     * @param mesh the Mesh to modify (not null,
-     * mode=Triangles/TriangleFan/TriangleStrip)
+     * @param indexList the IndexBuffer to convert (not null, size a multiple of
+     * 3, unaffected)
+     * @param numVertices the number of vertices in the mesh (&gt;0)
+     * @return a new buffer
      */
-    public static void trianglesToLines(Mesh mesh) {
-        Validate.nonNull(mesh, "mesh");
-        Validate.require(hasTriangles(mesh), "contain triangles");
+    public static IndexBuffer trianglesToLines(
+            IndexBuffer indexList, int numVertices) {
+        Validate.nonNull(indexList, "index list");
+        Validate.require(
+                (indexList.size() % MyMesh.vpt) == 0, "size a multiple of 3");
+        Validate.positive(numVertices, "number of vertices");
 
-        IndexBuffer indexList = mesh.getIndicesAsList();
-        int numTriangles = indexList.size() / vpt;
-        Set<IntPair> edgeSet = new HashSet<>(vpt * numTriangles);
+        int numTriangles = indexList.size() / MyMesh.vpt;
+        Set<IntPair> edgeSet = new HashSet<>(MyMesh.vpt * numTriangles);
         for (int triIndex = 0; triIndex < numTriangles; ++triIndex) {
-            int intOffset = vpt * triIndex;
+            int intOffset = MyMesh.vpt * triIndex;
             int ti0 = indexList.get(intOffset);
             int ti1 = indexList.get(intOffset + 1);
             int ti2 = indexList.get(intOffset + 2);
@@ -1524,19 +1528,38 @@ public static void trianglesToLines(Mesh mesh) {
             edgeSet.add(new IntPair(ti1, ti2));
         }
         int numEdges = edgeSet.size();
-        int numIndices = vpe * numEdges;
+        int numIndices = MyMesh.vpe * numEdges;
+
+        IndexBuffer result
+                = IndexBuffer.createIndexBuffer(numVertices, numIndices);
+        for (IntPair edge : edgeSet) {
+            result.put(edge.smaller());
+            result.put(edge.larger());
+        }
+        Buffer ibData = result.getBuffer();
+        ibData.flip();
+
+        return result;
+    }
+
+    /**
+     * Convert mesh triangles to lines.
+     *
+     * @param mesh the Mesh to modify (not null,
+     * mode=Triangles/TriangleFan/TriangleStrip)
+     */
+    public static void trianglesToLines(Mesh mesh) {
+        Validate.nonNull(mesh, "mesh");
+        Validate.require(hasTriangles(mesh), "contain triangles");
+
+        IndexBuffer indexList = mesh.getIndicesAsList();
         int numVertices = mesh.getVertexCount();
+        IndexBuffer ib = trianglesToLines(indexList, numVertices);
 
         mesh.clearBuffer(VertexBuffer.Type.Index);
 
-        IndexBuffer ib = IndexBuffer.createIndexBuffer(numVertices, numIndices);
-        for (IntPair edge : edgeSet) {
-            ib.put(edge.smaller());
-            ib.put(edge.larger());
-        }
         VertexBuffer.Format ibFormat = ib.getFormat();
         Buffer ibData = ib.getBuffer();
-        ibData.flip();
         mesh.setBuffer(VertexBuffer.Type.Index, vpe, ibFormat, ibData);
 
         mesh.setMode(Mesh.Mode.Lines);