GLFboStack.java :  » Java-2D » mt4j » org » mt4j » util » opengl » Java Open Source

/***********************************************************************
 * mt4j Copyright (c) 2008 - 2010 Christopher Ruff, Fraunhofer-Gesellschaft All rights reserved.
 *  
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 ***********************************************************************/
package org.mt4j.util.opengl;

import java.util.Stack;

import javax.media.opengl.GL;
import javax.media.opengl.glu.GLU;

import org.mt4j.util.logging.ILogger;
import org.mt4j.util.logging.MTLoggerFactory;

/**
 * The FBO stack manages the current opengl drawing target. It allows to switch drawing to/from different
 * frame buffer objects.
 * Usage:<br>
 * <br>GLFboStack.getInstance(gl).pushFBO(); //saves the current render target/frame buffer 
 * <br>GLFboStack.getInstance(gl).useFBO(glFBO); //changes to another frame buffer
 * <br>GLFboStack.getInstance(gl).popFBO() //switches back to the previously saved frame buffer
 * @author Christopher Ruff
 */
public class GLFboStack{
  /** The Constant logger. */
  private static final ILogger logger = MTLoggerFactory.getLogger(GLFboStack.class.getName());
  static{
    logger.setLevel(ILogger.ERROR);
  }
  
  /** The gl. */
  public GL gl;
  
  /** The current fbo. */
  protected int currentFBO;
  
  /** The fbo name stack. */
  protected Stack<Integer> fboNameStack;
  
  /** The instance. */
  private static GLFboStack instance = null;

  /**
   * Instantiates a new gL fbo stack.
   * @param gl the gl
   */
  private GLFboStack(GL gl){
    this.gl = gl;
    fboNameStack = new Stack<Integer>();
    currentFBO = 0;
  }
  
  /**
   * Gets the single instance of GLFboStack.
   *
   * @return single instance of GLFboStack
   */
  public static GLFboStack getInstance(){
    if (instance == null){
      instance = new GLFboStack(GLU.getCurrentGL());
      return instance;
    }else{
      return instance;
    }
  }

  /**
   * Pushes the currently used render target ID on the stack.
   */
  public void pushFBO(){
    fboNameStack.push(currentFBO);
  }

  /**
   * Binds the specified render target ID and sets it as current.
   * 
   * @param fbo the fbo
   */
  public void useFBO(int fbo){
    currentFBO = fbo;
    gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, currentFBO);
  }

  /**
   * Binds the specified frame buffer object and sets it as current.
   * 
   * @param fbo the fbo
   */
  public void useFBO(GLFBO fbo){
    currentFBO = fbo.getName();
    fbo.bind();
  }
  
  /**
   * Peek fbo.
   *
   * @return the int
   */
  public int peekFBO(){
    if (fboNameStack.isEmpty()){
      return 0;
    }else{
//      return fboNameStack.peek();
      return currentFBO;
    }
  }

  //NOTE THIS UNBINDS A CURRENT FBO IF SET! -> no need for calling unbind()!
  /**
   * Pops the fbo.
   * This switches back (binds) to the formely pushed fbo. 
   * <br>NOTE: THIS UNBINDS A CURRENT FBO IF SET! -> no need for calling unbind()!
   */
  public void popFBO(){
    if (fboNameStack.isEmpty()){
      logger.error("Trying to pop() from an empty framebuffer stack!"); //TODO -> just bind 0 !?
    }else{
      currentFBO = fboNameStack.pop();
      gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, currentFBO);
    }
  }
  
}