LiteCraft/src/main/java/io/github/hydos/ginger/engine/postprocessing/Fbo.java

package io.github.hydos.ginger.engine.postprocessing;

import java.nio.ByteBuffer;

import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.GL12;
import org.lwjgl.opengl.GL14;
import org.lwjgl.opengl.GL30;

import com.github.halotroop.litecraft.LiteCraftMain;

public class Fbo
{
	public static final int NONE = 0;
	public static final int DEPTH_TEXTURE = 1;
	public static final int DEPTH_RENDER_BUFFER = 2;
	private final int width;
	private final int height;
	private int frameBuffer;
	private int colourTexture;
	private int depthTexture;
	private int depthBuffer;
	private int colourBuffer;

	/** Creates an FBO of a specified width and height, with the desired type of
	 * depth buffer attachment.
	 * 
	 * @param width
	 *                        - the width of the FBO.
	 * @param height
	 *                        - the height of the FBO.
	 * @param depthBufferType
	 *                        - an int indicating the type of depth buffer attachment that
	 *                        this FBO should use. */
	public Fbo(int width, int height, int depthBufferType)
	{
		this.width = width;
		this.height = height;
		initialiseFrameBuffer(depthBufferType);
	}

	/** Deletes the frame buffer and its attachments when the game closes. */
	public void cleanUp()
	{
		GL30.glDeleteFramebuffers(frameBuffer);
		GL11.glDeleteTextures(colourTexture);
		GL11.glDeleteTextures(depthTexture);
		GL30.glDeleteRenderbuffers(depthBuffer);
		GL30.glDeleteRenderbuffers(colourBuffer);
	}

	/** Binds the frame buffer, setting it as the current render target. Anything
	 * rendered after this will be rendered to this FBO, and not to the screen. */
	public void bindFrameBuffer()
	{
		GL30.glBindFramebuffer(GL30.GL_DRAW_FRAMEBUFFER, frameBuffer);
		GL11.glViewport(0, 0, width, height);
	}

	/** Unbinds the frame buffer, setting the default frame buffer as the current
	 * render target. Anything rendered after this will be rendered to the
	 * screen, and not this FBO. */
	public void unbindFrameBuffer()
	{
		GL30.glBindFramebuffer(GL30.GL_FRAMEBUFFER, 0);
		GL11.glViewport(0, 0, LiteCraftMain.width, LiteCraftMain.height);
	}

	/** Binds the current FBO to be read from (not used in tutorial 43). */
	public void bindToRead()
	{
		GL11.glBindTexture(GL11.GL_TEXTURE_2D, 0);
		GL30.glBindFramebuffer(GL30.GL_READ_FRAMEBUFFER, frameBuffer);
		GL11.glReadBuffer(GL30.GL_COLOR_ATTACHMENT0);
	}

	/** @return The ID of the texture containing the colour buffer of the FBO. */
	public int getColourTexture()
	{ return colourTexture; }

	/** @return The texture containing the FBOs depth buffer. */
	public int getDepthTexture()
	{ return depthTexture; }

	/** Creates the FBO along with a colour buffer texture attachment, and
	 * possibly a depth buffer.
	 * 
	 * @param type
	 *             - the type of depth buffer attachment to be attached to the
	 *             FBO. */
	private void initialiseFrameBuffer(int type)
	{
		createFrameBuffer();
		createTextureAttachment();
		if (type == DEPTH_RENDER_BUFFER)
		{
			createDepthBufferAttachment();
		}
		else if (type == DEPTH_TEXTURE)
		{ createDepthTextureAttachment(); }
		unbindFrameBuffer();
	}

	/** Creates a new frame buffer object and sets the buffer to which drawing
	 * will occur - colour attachment 0. This is the attachment where the colour
	 * buffer texture is. */
	private void createFrameBuffer()
	{
		frameBuffer = GL30.glGenFramebuffers();
		GL30.glBindFramebuffer(GL30.GL_FRAMEBUFFER, frameBuffer);
		GL11.glDrawBuffer(GL30.GL_COLOR_ATTACHMENT0);
	}

	/** Creates a texture and sets it as the colour buffer attachment for this
	 * FBO. */
	private void createTextureAttachment()
	{
		colourTexture = GL11.glGenTextures();
		GL11.glBindTexture(GL11.GL_TEXTURE_2D, colourTexture);
		GL11.glTexImage2D(GL11.GL_TEXTURE_2D, 0, GL11.GL_RGBA8, width, height, 0, GL11.GL_RGBA, GL11.GL_UNSIGNED_BYTE,
			(ByteBuffer) null);
		GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_LINEAR);
		GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_LINEAR);
		GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL12.GL_CLAMP_TO_EDGE);
		GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_T, GL12.GL_CLAMP_TO_EDGE);
		GL30.glFramebufferTexture2D(GL30.GL_FRAMEBUFFER, GL30.GL_COLOR_ATTACHMENT0, GL11.GL_TEXTURE_2D, colourTexture,
			0);
	}

	/** Adds a depth buffer to the FBO in the form of a texture, which can later
	 * be sampled. */
	private void createDepthTextureAttachment()
	{
		depthTexture = GL11.glGenTextures();
		GL11.glBindTexture(GL11.GL_TEXTURE_2D, depthTexture);
		GL11.glTexImage2D(GL11.GL_TEXTURE_2D, 0, GL14.GL_DEPTH_COMPONENT24, width, height, 0, GL11.GL_DEPTH_COMPONENT,
			GL11.GL_FLOAT, (ByteBuffer) null);
		GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_LINEAR);
		GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_LINEAR);
		GL30.glFramebufferTexture2D(GL30.GL_FRAMEBUFFER, GL30.GL_DEPTH_ATTACHMENT, GL11.GL_TEXTURE_2D, depthTexture, 0);
	}

	/** Adds a depth buffer to the FBO in the form of a render buffer. This can't
	 * be used for sampling in the shaders. */
	private void createDepthBufferAttachment()
	{
		depthBuffer = GL30.glGenRenderbuffers();
		GL30.glBindRenderbuffer(GL30.GL_RENDERBUFFER, depthBuffer);
		GL30.glRenderbufferStorage(GL30.GL_RENDERBUFFER, GL14.GL_DEPTH_COMPONENT24, width, height);
		GL30.glFramebufferRenderbuffer(GL30.GL_FRAMEBUFFER, GL30.GL_DEPTH_ATTACHMENT, GL30.GL_RENDERBUFFER,
			depthBuffer);
	}
}