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/*
 * Copyright (c) 2009-2021 jMonkeyEngine
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
 *   may be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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 */
package com.jme3.scene.mesh;

import com.jme3.scene.Mesh.Mode;
import com.jme3.scene.VertexBuffer.Format;

import java.nio.Buffer;

/**
 * IndexBuffer implementation that generates vertex indices sequentially
 * based on a specific Mesh {@link Mode}.
 * The generated indices are as if the mesh is in the given mode
 * but contains no index buffer, thus this implementation will
 * return the indices if the index buffer was there and contained sequential
 * triangles.
 * Example:
 * 
    *
  • {@link Mode#Triangles}: 0, 1, 2 | 3, 4, 5 | 6, 7, 8 | ...
  • *
  • {@link Mode#TriangleStrip}: 0, 1, 2 | 2, 1, 3 | 2, 3, 4 | ...
  • *
  • {@link Mode#TriangleFan}: 0, 1, 2 | 0, 2, 3 | 0, 3, 4 | ...
  • *
* * @author Kirill Vainer */ public class VirtualIndexBuffer extends IndexBuffer { protected int numVerts = 0; protected int numIndices = 0; protected Mode meshMode; protected int position = 0; public VirtualIndexBuffer(int numVerts, Mode meshMode) { this.numVerts = numVerts; this.meshMode = meshMode; switch (meshMode) { case Points: numIndices = numVerts; return; case LineLoop: numIndices = numVerts * 2; return; case LineStrip: numIndices = (numVerts - 1) * 2; return; case Lines: numIndices = numVerts; return; case TriangleFan: numIndices = (numVerts - 2) * 3; return; case TriangleStrip: numIndices = (numVerts - 2) * 3; return; case Triangles: numIndices = numVerts; return; case Hybrid: throw new UnsupportedOperationException(); } } @Override public int get() { int i = get(position); position++; return i; } @Override public void rewind() { position = 0; } @Override public int remaining() { return numIndices - position; } @Override public int get(int i) { if (meshMode == Mode.Triangles || meshMode == Mode.Lines || meshMode == Mode.Points) { return i; } else if (meshMode == Mode.LineStrip) { return (i + 1) / 2; } else if (meshMode == Mode.LineLoop) { return (i == (numIndices - 1)) ? 0 : ((i + 1) / 2); } else if (meshMode == Mode.TriangleStrip) { int triIndex = i / 3; int vertIndex = i % 3; boolean isBack = (i / 3) % 2 == 1; if (!isBack) { return triIndex + vertIndex; } else { switch (vertIndex) { case 0: return triIndex + 1; case 1: return triIndex; case 2: return triIndex + 2; default: throw new AssertionError(); } } } else if (meshMode == Mode.TriangleFan) { int vertIndex = i % 3; if (vertIndex == 0) { return 0; } else { return (i / 3) + vertIndex; } } else { throw new UnsupportedOperationException(); } } @Override public IndexBuffer put(int i, int value) { throw new UnsupportedOperationException("Does not represent index buffer"); } @Override public int size() { return numIndices; } @Override public Buffer getBuffer() { return null; } @Override public IndexBuffer put(int value) { throw new UnsupportedOperationException("Does not represent index buffer"); } @Override public Format getFormat() { // return largest size return Format.UnsignedInt; } }




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