Android Open Source - opengl Square

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License

The source code is released under:

Apache License

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Java Source Code

package edu.cs4730.OpenGlDemo;
/*from w w w . j a  v a2  s  .co  m*/
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;

import javax.microedition.khronos.opengles.GL10;

public class Square {
  // Our vertices.
  private float vertices[] = {
          -1.0f,  1.0f, 0.0f,  // 0, Top Left
          -1.0f, -1.0f, 0.0f,  // 1, Bottom Left
           1.0f, -1.0f, 0.0f,  // 2, Bottom Right
           1.0f,  1.0f, 0.0f,  // 3, Top Right
    };

  // The order we like to connect them.
  private short[] indices = { 0, 1, 2, 0, 2, 3 };

  // Our vertex buffer.
  private FloatBuffer vertexBuffer;

  // Our index buffer.
  private ShortBuffer indexBuffer;

  public Square() {
    // a float is 4 bytes, therefore we multiply the number if
    // vertices with 4.
    ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
    vbb.order(ByteOrder.nativeOrder());
    vertexBuffer = vbb.asFloatBuffer();
    vertexBuffer.put(vertices);
    vertexBuffer.position(0);

    // short is 2 bytes, therefore we multiply the number if
    // vertices with 2.
    ByteBuffer ibb = ByteBuffer.allocateDirect(indices.length * 2);
    ibb.order(ByteOrder.nativeOrder());
    indexBuffer = ibb.asShortBuffer();
    indexBuffer.put(indices);
    indexBuffer.position(0);
  }

  /**
   * This function draws our square on screen.
   * @param gl
   */
  public void draw(GL10 gl) {
    //set a color other then white, which is blue/purple
    gl.glColor4f(0.5f, 0.5f, 1.0f, 1.0f); // 0x8080FFFF
    // Counter-clockwise winding.
    gl.glFrontFace(GL10.GL_CCW); // OpenGL docs
    // Enable face culling.
    gl.glEnable(GL10.GL_CULL_FACE); // OpenGL docs
    // What faces to remove with the face culling.
    gl.glCullFace(GL10.GL_BACK); // OpenGL docs

    // Enabled the vertices buffer for writing and to be used during
    // rendering.
    gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);// OpenGL docs.
    // Specifies the location and data format of an array of vertex
    // coordinates to use when rendering.
    gl.glVertexPointer(3, GL10.GL_FLOAT, 0, // OpenGL docs
                                 vertexBuffer);

    gl.glDrawElements(GL10.GL_TRIANGLES, indices.length,// OpenGL docs
          GL10.GL_UNSIGNED_SHORT, indexBuffer);

    // Disable the vertices buffer.
    gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); // OpenGL docs
    // Disable face culling.
    gl.glDisable(GL10.GL_CULL_FACE); // OpenGL docs
  }

}

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