Render to Texture with Frame Buffer Objects (FBO)
From LWJGL
Example on how to render to texture with a Frame Buffer Object (FBO).
Original tutorial found here.
/********************************************************
* *
* Overlords Tutorial - 01 *
* http://www.flashbang.se *
* 2006 *
* *
* ported by kappaOne *
* from http://www.flashbang.se/archives/48 *
*********************************************************/
import org.lwjgl.LWJGLException;
import org.lwjgl.Sys;
import org.lwjgl.input.Keyboard;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GLContext;
import org.lwjgl.opengl.GL14;
import org.lwjgl.util.glu.GLU;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.EXTFramebufferObject.*;
public class FBOExample {
float angle;
int colorTextureID;
int framebufferID;
int depthRenderBufferID;
/** time at last frame */
long lastFrame;
/** frames per second */
int fps;
/** last fps time */
long lastFPS;
/** is VSync Enabled */
boolean vsyncEnabled;
public void start() {
try {
Display.setDisplayMode(new DisplayMode(512, 512));
Display.create();
} catch (LWJGLException e) {
e.printStackTrace();
System.exit(0);
}
initGL(); // init OpenGL
getDelta(); // call once before loop to initialise lastFrame
lastFPS = getTime(); // call before loop to initialise fps timer
while (!Display.isCloseRequested()) {
int delta = getDelta();
update(delta);
renderGL();
Display.update();
Display.sync(60); // cap fps to 60fps
}
Display.destroy();
}
public void update(int delta) {
// rotate box
angle += 0.15f * delta;
while (Keyboard.next()) {
if (Keyboard.getEventKeyState()) {
if (Keyboard.getEventKey() == Keyboard.KEY_F) {
setDisplayMode(800, 600, !Display.isFullscreen());
}
else if (Keyboard.getEventKey() == Keyboard.KEY_V) {
vsyncEnabled = !vsyncEnabled;
Display.setVSyncEnabled(vsyncEnabled);
}
}
}
updateFPS(); // update FPS Counter
}
public void initGL() {
glViewport (0, 0, 512, 512); // Reset The Current Viewport
glMatrixMode (GL_PROJECTION); // Select The Projection Matrix
glLoadIdentity (); // Reset The Projection Matrix
GLU.gluPerspective (45.0f, 512f/512f, 1.0f, 100.0f); // Calculate The Aspect Ratio Of The Window
glMatrixMode (GL_MODELVIEW); // Select The Modelview Matrix
glLoadIdentity (); // Reset The Modelview Matrix
// Start Of User Initialization
angle = 0.0f; // Set Starting Angle To Zero
glClearColor (0.0f, 0.0f, 0.0f, 0.5f); // Black Background
glClearDepth (1.0f); // Depth Buffer Setup
glDepthFunc (GL_LEQUAL); // The Type Of Depth Testing (Less Or Equal)
glEnable (GL_DEPTH_TEST); // Enable Depth Testing
glShadeModel (GL_SMOOTH); // Select Smooth Shading
glHint (GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Set Perspective Calculations To Most Accurate
// check if GL_EXT_framebuffer_object can be use on this system
if (!GLContext.getCapabilities().GL_EXT_framebuffer_object) {
System.out.println("FBO not supported!!!");
System.exit(0);
}
else {
System.out.println("FBO is supported!!!");
// init our fbo
framebufferID = glGenFramebuffersEXT(); // create a new framebuffer
colorTextureID = glGenTextures(); // and a new texture used as a color buffer
depthRenderBufferID = glGenRenderbuffersEXT(); // And finally a new depthbuffer
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebufferID); // switch to the new framebuffer
// initialize color texture
glBindTexture(GL_TEXTURE_2D, colorTextureID); // Bind the colorbuffer texture
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); // make it linear filterd
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 512, 512, 0,GL_RGBA, GL_INT, (java.nio.ByteBuffer) null); // Create the texture data
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT,GL_COLOR_ATTACHMENT0_EXT,GL_TEXTURE_2D, colorTextureID, 0); // attach it to the framebuffer
// initialize depth renderbuffer
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthRenderBufferID); // bind the depth renderbuffer
glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL14.GL_DEPTH_COMPONENT24, 512, 512); // get the data space for it
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT,GL_DEPTH_ATTACHMENT_EXT,GL_RENDERBUFFER_EXT, depthRenderBufferID); // bind it to the renderbuffer
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); // Swithch back to normal framebuffer rendering
}
}
public void renderGL() {
// FBO render pass
glViewport (0, 0, 512, 512); // set The Current Viewport to the fbo size
glBindTexture(GL_TEXTURE_2D, 0); // unlink textures because if we dont it all is gonna fail
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebufferID); // switch to rendering on our FBO
glClearColor (1.0f, 0.0f, 0.0f, 0.5f);
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer on the fbo to red
glLoadIdentity (); // Reset The Modelview Matrix
glTranslatef (0.0f, 0.0f, -6.0f); // Translate 6 Units Into The Screen and then rotate
glRotatef(angle,0.0f,1.0f,0.0f);
glRotatef(angle,1.0f,0.0f,0.0f);
glRotatef(angle,0.0f,0.0f,1.0f);
glColor3f(1,1,0); // set color to yellow
drawBox(); // draw the box
// Normal render pass, draw cube with texture
glEnable(GL_TEXTURE_2D); // enable texturing
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); // switch to rendering on the framebuffer
glClearColor (0.0f, 1.0f, 0.0f, 0.5f);
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer on the framebuffer to black
glBindTexture(GL_TEXTURE_2D, colorTextureID); // bind our FBO texture
glViewport (0, 0, 512, 512); // set The Current Viewport
glLoadIdentity (); // Reset The Modelview Matrix
glTranslatef (0.0f, 0.0f, -6.0f); // Translate 6 Units Into The Screen and then rotate
glRotatef(angle,0.0f,1.0f,0.0f);
glRotatef(angle,1.0f,0.0f,0.0f);
glRotatef(angle,0.0f,0.0f,1.0f);
glColor3f(1,1,1); // set the color to white
drawBox(); // draw the box
glDisable(GL_TEXTURE_2D);
glFlush ();
}
public void drawBox() {
// this func just draws a perfectly normal box with some texture coordinates
glBegin(GL_QUADS);
// Front Face
glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); // Bottom Left Of The Texture and Quad
glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); // Bottom Right Of The Texture and Quad
glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 1.0f); // Top Right Of The Texture and Quad
glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f); // Top Left Of The Texture and Quad
// Back Face
glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f); // Bottom Right Of The Texture and Quad
glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); // Top Right Of The Texture and Quad
glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); // Top Left Of The Texture and Quad
glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f); // Bottom Left Of The Texture and Quad
// Top Face
glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); // Top Left Of The Texture and Quad
glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, 1.0f, 1.0f); // Bottom Left Of The Texture and Quad
glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, 1.0f, 1.0f); // Bottom Right Of The Texture and Quad
glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); // Top Right Of The Texture and Quad
// Bottom Face
glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f); // Top Right Of The Texture and Quad
glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f); // Top Left Of The Texture and Quad
glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); // Bottom Left Of The Texture and Quad
glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); // Bottom Right Of The Texture and Quad
// Right face
glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f); // Bottom Right Of The Texture and Quad
glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); // Top Right Of The Texture and Quad
glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 1.0f); // Top Left Of The Texture and Quad
glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); // Bottom Left Of The Texture and Quad
// Left Face
glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f); // Bottom Left Of The Texture and Quad
glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); // Bottom Right Of The Texture and Quad
glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f); // Top Right Of The Texture and Quad
glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); // Top Left Of The Texture and Quad
glEnd();
}
/**
* Set the display mode to be used
*
* @param width The width of the display required
* @param height The height of the display required
* @param fullscreen True if we want fullscreen mode
*/
public void setDisplayMode(int width, int height, boolean fullscreen) {
// return if requested DisplayMode is already set
if ((Display.getDisplayMode().getWidth() == width) &&
(Display.getDisplayMode().getHeight() == height) &&
(Display.isFullscreen() == fullscreen)) {
return;
}
try {
DisplayMode targetDisplayMode = null;
if (fullscreen) {
DisplayMode[] modes = Display.getAvailableDisplayModes();
int freq = 0;
for (int i=0;i<modes.length;i++) {
DisplayMode current = modes[i];
if ((current.getWidth() == width) && (current.getHeight() == height)) {
if ((targetDisplayMode == null) || (current.getFrequency() >= freq)) {
if ((targetDisplayMode == null) || (current.getBitsPerPixel() > targetDisplayMode.getBitsPerPixel())) {
targetDisplayMode = current;
freq = targetDisplayMode.getFrequency();
}
}
// if we've found a match for bpp and frequence against the
// original display mode then it's probably best to go for this one
// since it's most likely compatible with the monitor
if ((current.getBitsPerPixel() == Display.getDesktopDisplayMode().getBitsPerPixel()) &&
(current.getFrequency() == Display.getDesktopDisplayMode().getFrequency())) {
targetDisplayMode = current;
break;
}
}
}
} else {
targetDisplayMode = new DisplayMode(width,height);
}
if (targetDisplayMode == null) {
System.out.println("Failed to find value mode: "+width+"x"+height+" fs="+fullscreen);
return;
}
Display.setDisplayMode(targetDisplayMode);
Display.setFullscreen(fullscreen);
} catch (LWJGLException e) {
System.out.println("Unable to setup mode "+width+"x"+height+" fullscreen="+fullscreen + e);
}
}
/**
* Calculate how many milliseconds have passed
* since last frame.
*
* @return milliseconds passed since last frame
*/
public int getDelta() {
long time = getTime();
int delta = (int) (time - lastFrame);
lastFrame = time;
return delta;
}
/**
* Get the accurate system time
*
* @return The system time in milliseconds
*/
public long getTime() {
return (Sys.getTime() * 1000) / Sys.getTimerResolution();
}
/**
* Calculate the FPS and set it in the title bar
*/
public void updateFPS() {
if (getTime() - lastFPS > 1000) {
Display.setTitle("FPS: " + fps);
fps = 0;
lastFPS += 1000;
}
fps++;
}
public static void main(String[] argv) {
FBOExample fboExample = new FBOExample();
fboExample.start();
}
}
