IndexBuffer.java

// Copyright 2008 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.android.stardroid.renderer.util;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.ShortBuffer;

import javax.microedition.khronos.opengles.GL10;
import javax.microedition.khronos.opengles.GL11;

public class IndexBuffer {
  public IndexBuffer(int numVertices) {
    this(numVertices, false);
  }

  public IndexBuffer() {
    mNumIndices = 0;
  }

  public IndexBuffer(boolean useVBO) {
    mNumIndices = 0;
    mUseVbo = useVBO;
  }

  public IndexBuffer(int numVertices, boolean useVbo) {
    mUseVbo = useVbo;
    reset(numVertices);
  }

  public int size() {
    return mNumIndices;
  }

  public void reset(int numVertices) {
    mNumIndices = numVertices;
    regenerateBuffer();
  }

  // Call this when we have to re-create the surface and reloading all OpenGL resources.
  public void reload() {
    mGLBuffer.reload();
  }

  private void regenerateBuffer() {
    if (mNumIndices == 0) {
      return;
    }

    ByteBuffer bb = ByteBuffer.allocateDirect(2 * mNumIndices);
    bb.order(ByteOrder.nativeOrder());
    ShortBuffer ib = bb.asShortBuffer();
    ib.position(0);
    mIndexBuffer = ib;
  }

  public void addIndex(short index) {
    mIndexBuffer.put(index);
  }

  public void draw(GL10 gl, int primitiveType) {
    if (mNumIndices == 0) {
      return;
    }
    mIndexBuffer.position(0);
    if (mUseVbo && GLBuffer.canUseVBO()) {
      GL11 gl11 = (GL11)gl;
      mGLBuffer.bind(gl11, mIndexBuffer, 2 * mIndexBuffer.capacity());
      gl11.glDrawElements(primitiveType, size(), GL10.GL_UNSIGNED_SHORT, 0);
      GLBuffer.unbind(gl11);
    } else {
      gl.glDrawElements(primitiveType, size(), GL10.GL_UNSIGNED_SHORT, mIndexBuffer);
    }
  }

  private ShortBuffer mIndexBuffer = null;
  private int mNumIndices = 0;
  private GLBuffer mGLBuffer = new GLBuffer(GL11.GL_ELEMENT_ARRAY_BUFFER);
  private boolean mUseVbo = false;
}