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King of Men

OpenGL 'Stripes' in heightmap terrain

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I am experimenting with a heightmap for my terrain. As a first pass, I'm just drawing a green wireframe; texturing is the next step. I've gotten it to work, more or less. The problem is that, at certain view angles, there are large black gaps in my nice green (flat) terrain, which I don't understand. Some screenies may make it clearer: Photobucket - Video and Image Hosting This is what things ought to look like. But if you change the camera azimuth angle just a touch, you get this: Photobucket - Video and Image Hosting Great big ravines! Now, the first thing I tried was to move my viewpoint to float above the landscape, looking straight down at it. When I do this, I do not see any gaps. In the screenies I'm showing here, the viewpoint is 8 units above the plane (the vertices are at integral points) looking off at a distant point, also 8 units above the landscape. Is this, by any chance, a known problem for which a known fix exists? In case it's helpful, here's my code:
import java.awt.*;
import net.java.games.jogl.*;
import java.awt.event.*;
import java.io.IOException;
import java.nio.IntBuffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import net.java.games.jogl.util.BufferUtils;
import net.java.games.jogl.util.GLUT;
import static java.lang.Math.*;

final class GUI extends Frame {

  private static boolean quit;
  private GLCanvas mainDisplay;
  private Rectangle mainDisplayRectangle;

  private GLCanvas statusDisplay;
  private Rectangle statusDisplayRectangle;

  // Camera-control variables
  private double polar;
  private double azimuth;  // Angle with x axis
  private double zoom;

  // Stuff for perspective
  private double displayRatio;
  private double angleOfScreen;

  // Cache for use in input
  private GL gl;
  private GLU glu;
  private GLUT glut = new GLUT();

  // Used in getting ingame coordinates from mouse clicks.
  // I don't understand why I need to cache them, but if I
  // call the getters in mouseClicked, I get all zeroes. 
  private int[]    view = new int[4];
  private double[] mode = new double[16];
  private double[] proj = new double[16];
  private static boolean paused = true;
  private long delay = 500;

  private Titan theTitan;
  private HeightMap myMap;

  public static void main (String[] args) {
    GUI g = new GUI();

  public GUI () {
    Rectangle bounds = getGraphicsConfiguration().getBounds();
    setSize(bounds.width, bounds.height);

    quit = false;
    theTitan = new Titan();

    // TODO : Do away with hardcoding. 
    mainDisplayRectangle = new Rectangle(200, 0, bounds.width - 200, bounds.height);
    MainDisplayDrawer l = new MainDisplayDrawer();
    mainDisplay = GLDrawableFactory.getFactory().createGLCanvas(new GLCapabilities());

    statusDisplayRectangle = new Rectangle(0, 0, 200, bounds.height);
    StatusDisplayDrawer p = new StatusDisplayDrawer();
    statusDisplay = GLDrawableFactory.getFactory().createGLCanvas(new GLCapabilities());

    // TODO : Possibly in a separate class? 
    MainDisplayMouseListener disMouse = new MainDisplayMouseListener();

  public void waitForInput () {
    long elapsedTime = System.currentTimeMillis();
    long currentTime = 0;

    while (!quit) {
      currentTime = System.currentTimeMillis();
      //if (currentTime - elapsedTime < delay) continue;


      if (paused) continue;
      elapsedTime = System.currentTimeMillis();

  public static void doQuit () {quit = true;}
  public static void togglePause () {paused = !paused;}

  final class MainDisplayMouseListener implements MouseListener {
    public void mouseClicked (MouseEvent e) {}
    public void mousePressed (MouseEvent e) {}
    public void mouseReleased (MouseEvent e) {}
    public void mouseEntered (MouseEvent e) {}
    public void mouseExited (MouseEvent e) {}

  final class MainDisplayDrawer implements GLEventListener {
    private byte[] testTexture;

    public MainDisplayDrawer () {}

    public void init (GLDrawable drawable) {
      gl = drawable.getGL(); 
      myMap = new HeightMap("heightmap.bmp", gl);
      gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
      gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT);
      gl.glViewport(0, 0, mainDisplayRectangle.width, mainDisplayRectangle.height);
      gl.glGetIntegerv(gl.GL_VIEWPORT, view);

      displayRatio = (1.0 * mainDisplayRectangle.width) / mainDisplayRectangle.height;
      angleOfScreen = 10;
    public void display (GLDrawable drawable) {
      gl = drawable.getGL(); 
      glu = drawable.getGLU(); 

      glu.gluPerspective(angleOfScreen, displayRatio, 0.01, zoom);

      gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT);

      gl.glGetIntegerv(gl.GL_VIEWPORT, view);
      gl.glGetDoublev(gl.GL_PROJECTION_MATRIX, proj);
      gl.glGetDoublev(gl.GL_MODELVIEW_MATRIX, mode);


      if (paused) {
	gl.glColor3d(1.0, 1.0, 1.0); 
	gl.glRasterPos2d(0.5*mainDisplayRectangle.width, mainDisplayRectangle.height-15);
	glut.glutBitmapString(gl, glut.BITMAP_TIMES_ROMAN_10, "Game Paused");
    // These two methods should never be called.
    public void reshape (GLDrawable drawable, int i, int x, int width, int height) {}
    public void displayChanged (GLDrawable drawable, boolean modeChanged, boolean deviceChanged) {}

  final class StatusDisplayDrawer implements GLEventListener {
    public StatusDisplayDrawer () {}

    public void init (GLDrawable drawable) {
      GL logl = drawable.getGL(); 
      logl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
      logl.glViewport(0, 0, statusDisplayRectangle.width, statusDisplayRectangle.height);
      logl.glOrtho(0, statusDisplayRectangle.width, 0, statusDisplayRectangle.height, -1, 1);	 
    public void display (GLDrawable drawable) {
      GL logl = drawable.getGL(); 
    // These two methods should never be called.
    public void reshape (GLDrawable drawable, int i, int x, int width, int height) {}
    public void displayChanged (GLDrawable drawable, boolean modeChanged, boolean deviceChanged) {}

final class GLRectangle extends Rectangle {

  public GLRectangle (int ax, int ay, int aw, int ah) {
    super(ax, ay, aw, ah);

 public boolean contains (int ax, int ay) {
    if (ax < x) return false;
    if (ax > x + width) return false;

    // Note kludge to convert Java to OpenGL
    if (ay > y) return false;
    if (ay < y - height) return false;
    return true; 

class MyButton {

  private GLRectangle location;
  private byte[] picture;

  public MyButton (GLRectangle r) {
    location = r;
    picture = new byte[r.height*r.width*4];
    java.util.Arrays.fill(picture, (byte) -1);

  public void setPicture (byte[] a) {
    picture = a;

  public void draw (GL gl) {
    gl.glRasterPos2i(location.x, location.y);
    gl.glDrawPixels (location.width, location.height, gl.GL_RGBA, gl.GL_UNSIGNED_BYTE, picture);

  public boolean contains (int ax, int ay) {
    return location.contains(ax, ay);

final class MyButtonWithBooleanState extends MyButton {
  private byte[] truthPicture;
  private byte[] falsePicture;
  public MyButtonWithBooleanState (GLRectangle r) {
    truthPicture = new byte[r.height*r.width*4];
    falsePicture = new byte[r.height*r.width*4];

    for (int i = 0; i < truthPicture.length; i++) {
      if (i % 4 == 0) falsePicture = -1;
      else if (i % 4 == 1) truthPicture = -1;

  public void setState (boolean r) {
    if (r) setPicture(truthPicture);
    else setPicture(falsePicture);

final class Titan implements KeyListener {

  // Various body angles
  private double mainFacing;  // The way the feet are facing - same as the head if looking straight forward
  private double hipTwist;    // Azimuth angle of torso
  private double xpos;
  private double zpos;

  private Component head;
  private Component rightLeg;
  private Component leftLeg;
  private Component torso;
  private Component rightArm;
  private Component leftArm;

  private Component selectedComponent;

  public Titan () {
    head     = new Component(0, 8, -1);
    torso    = new Component(0, 6, 0);
    rightLeg = new Component(1, 3, 0);
    leftLeg  = new Component(-1, 3, 0);
    rightArm = new Component(1, 7, 0);
    leftArm  = new Component(-1, 7, 0);
    selectedComponent = head;
    xpos = 1530;
    zpos = 130;

  public void setView (GLU glu) {
    double eyeX = xpos + selectedComponent.relativeX * sin(mainFacing+hipTwist);
    double eyeY = selectedComponent.relativeY;
    double eyeZ = zpos - selectedComponent.relativeZ * cos(mainFacing+hipTwist);

    double lookAtX = 100*sin(mainFacing+hipTwist+selectedComponent.traverseAzimuth);
    double lookAtY = selectedComponent.relativeY * (1+sin(selectedComponent.traversePolar));
    double lookAtZ = -100*cos(mainFacing+hipTwist+selectedComponent.traverseAzimuth);
    double eyeX = xpos;
    double eyeY = 100;
    double eyeZ = zpos;

    double lookAtX = xpos;
    double lookAtY = 0;
    double lookAtZ = zpos + 1;
    glu.gluLookAt(eyeX, eyeY, eyeZ, 
		  lookAtX, lookAtY, lookAtZ, 
		  0, 1, 0);

  public void keyPressed (KeyEvent e) {}
  public void keyTyped (KeyEvent e) {}
  public void keyReleased (KeyEvent e) {
    switch (e.getKeyCode()) {
    case KeyEvent.VK_Q :
    case KeyEvent.VK_P :

    case KeyEvent.VK_KP_LEFT :
    case KeyEvent.VK_NUMPAD4 :
    case KeyEvent.VK_LEFT :
      mainFacing -= 0.02*PI;
    case KeyEvent.VK_KP_RIGHT :
    case KeyEvent.VK_RIGHT :
    case KeyEvent.VK_NUMPAD6 :
      mainFacing += 0.02*PI;

    case KeyEvent.VK_NUMPAD8 :
    case KeyEvent.VK_KP_UP :
    case KeyEvent.VK_UP :
      selectedComponent.traversePolar += 0.02*PI;
      //zpos += 10;

    case KeyEvent.VK_NUMPAD2 :
    case KeyEvent.VK_KP_DOWN :
    case KeyEvent.VK_DOWN :
      selectedComponent.traversePolar -= 0.02*PI;
      //zpos -= 10;

    default : break;

  final class Component {
    private int armor;
    private double relativeX;  // Position relative to titan feet
    private double relativeY;
    private double relativeZ;

    private double traversePolar;
    private double traverseAzimuth;

    private double minAzimuth;
    private double maxAzimuth;
    private double minPolar;
    private double maxPolar;

    public Component (double x, double y, double z) {
      relativeX = x;
      relativeY = y;
      relativeZ = z;

final class HeightMap {  
  private int[][] displayIndexes;

  public HeightMap (String fname, GL gl) {
    displayIndexes = new int[20][16];
    byte[] map = null;
    int side = 100;
    float[][] heights = new float[side][side];

    int currIndex = gl.glGenLists(displayIndexes.length*displayIndexes[0].length);
    if (currIndex == 0) {
      // TODO : Error handling
      System.out.println("Problem initialising display indices");

    for (int i = 0; i < displayIndexes.length; i++) {
      for (int j = 0; j < displayIndexes.length; j++) {
	try {
	  map = ImageHandler.loadImage(fname, (side-1)*i, (side-1)*j, side, side);
	catch (IOException e) {
	  // TODO : Again with the error handling - don't quite know what to do about this, though. 
	  System.out.println("Could not load " + fname);

	for (int x = 0; x < side; x++) { 
	  for (int y = 0; y < side; y++) { 
	    int mapIndex = y*side + 4*x;
	    byte one = map[mapIndex];
	    byte two = map[mapIndex+1];
	    byte thr = map[mapIndex+2];
	    byte fou = map[mapIndex+3]; 
            // Ok, ok, it's a kludge - fix it later. 
	    if      ((one ==  -1) && (two ==   -1) && (thr ==  -1) && (fou ==  -1)) heights[x][y] = 0;  // White
	    else if ((one ==   0) && (two == -128) && (thr ==   0) && (fou ==  -1)) heights[x][y] = 1;  // Green
	    else if ((one ==  -1) && (two ==    0) && (thr ==   0) && (fou ==  -1)) heights[x][y] = 2;  // Red
	    else if ((one ==   0) && (two ==    0) && (thr ==   0) && (fou ==  -1)) heights[x][y] = 3;  // Blue
	    else if ((one ==   0) && (two ==    0) && (thr ==  -1) && (fou ==  -1)) heights[x][y] = 4;  // Black

	displayIndexes[j] = currIndex;
	gl.glNewList(currIndex, gl.GL_COMPILE);
	int sid = side - 1;
	for (int x = 0; x < sid; x++) { 
	  gl.glVertex3f(sid*i + x + 1, heights[x+1][0], sid*j);

	  for (int y = 0; y < sid; y++) { 
	    gl.glVertex3f(sid*i + x, heights[x][y], sid*j + y);
	    gl.glVertex3f(sid*i + x, heights[x][y+1], sid*j + y + 1);
	    gl.glVertex3f(sid*i + x + 1, heights[x+1][y], sid*j + y);
	    gl.glVertex3f(sid*i + x + 1, heights[x+1][y+1], sid*j + y + 1);
	  gl.glVertex3f(sid*i + x, heights[x][sid], sid*j + sid);

  public void draw (GL gl) {
    gl.glColor3d(0, 1, 0);
    for (int i = 0; i < displayIndexes.length; i++) {
      for (int j = 0; j < displayIndexes.length; j++) {

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Ok, I just noticed and fixed the bug in the setView method, so now it'll look at things in a circle relative to the camera location and not the origin. But I still have the stripey bug, so that wasn't the problem. :)

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Is this terrain programming something you did yourself ? If so I know the answer (if you're using a professional terrain engine then I don't know!).

The sectors need to overlap. eg suppose you've divided your world into sectors of 20x20 vertices then if first sector is from

vector 1 to vector 20
then you've probably got the second sector from vector 21 to vector 40.

However, this means you'll have a gap or strip between vector 20 to vector 21
Where nothing is drawn.
You need to do the following:

vector 1 to vector 20
vector 20 to vector 40
vector 40 to vector 60 etc

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gl.glClearDepth(10000000); // is clamped to 1.0.
Manual: "Values specified by glClearDepth are clamped to the range [0,1]."

glu.gluPerspective(angleOfScreen, displayRatio, 0.01, zoom);
What is the value of zoom? Same as ClearDepth?
You get depth precision problems with such big values. Make it as small as possible.

You should avoid all double variants of OpenGL entry points.
Most, if not all, OpenGL implementations are implemented in float precision.

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Original post by ade-the-heat
The sectors need to overlap. eg suppose you've divided your world into sectors of 20x20 vertices then if first sector is from

vector 1 to vector 20
then you've probably got the second sector from vector 21 to vector 40.

Well, I did have such a bug at one point, yes. I believe that's no longer the cause of my problem, however.

gl.glClearDepth(10000000); // is clamped to 1.0.
Manual: "Values specified by glClearDepth are clamped to the range [0,1]."

Oops, thanks.

glu.gluPerspective(angleOfScreen, displayRatio, 0.01, zoom);
What is the value of zoom? Same as ClearDepth?
You get depth precision problems with such big values. Make it as small as possible.

Actually, now you mention it, I don't seem to initialise zoom at all. That's rather odd. I guess I'd better look into that when I get home. Thanks.

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    • By Hashbrown
      I've noticed in most post processing tutorials several shaders are used one after another: one for bloom, another for contrast, and so on. For example: 
      postprocessing.quad.bind() // Effect 1 effect1.shader.bind(); postprocessing.texture.bind(); postprocessing.quad.draw(); postprocessing.texture.unbind(); effect1.shader.unbind(); // Effect 2 effect2.shader.bind(); // ...and so on postprocessing.quad.unbind() Is this good practice, how many shaders can I bind and unbind before I hit performance issues? I'm afraid I don't know what the good practices are in open/webGL regarding binding and unbinding resources. 
      I'm guessing binding many shaders at post processing is okay since the scene has already been updated and I'm just working on a quad and texture at that moment. Or is it more optimal to put shader code in chunks and bind less frequently? I'd love to use several shaders at post though. 
      Another example of what I'm doing at the moment:
      1) Loop through GameObjects, bind its phong shader (send color, shadow, spec, normal samplers), unbind all.
      2) At post: bind post processor quad, and loop/bind through different shader effects, and so on ...
      Thanks all! 
    • By phil67rpg
      void collision(int v) { collision_bug_one(0.0f, 10.0f); glutPostRedisplay(); glutTimerFunc(1000, collision, 0); } void coll_sprite() { if (board[0][0] == 1) { collision(0); flag[0][0] = 1; } } void erase_sprite() { if (flag[0][0] == 1) { glColor3f(0.0f, 0.0f, 0.0f); glBegin(GL_POLYGON); glVertex3f(0.0f, 10.0f, 0.0f); glVertex3f(0.0f, 9.0f, 0.0f); glVertex3f(1.0f, 9.0f, 0.0f); glVertex3f(1.0f, 10.0f, 0.0f); glEnd(); } } I am using glutTimerFunc to wait a small amount of time to display a collision sprite before I black out the sprite. unfortunately my code only blacks out the said sprite without drawing the collision sprite, I have done a great deal of research on the glutTimerFunc and  animation.
    • By Lewa
      So, i stumbled upon the topic of gamma correction.
      So from what i've been able to gather: (Please correct me if i'm wrong)
      Old CRT monitors couldn't display color linearly, that's why gamma correction was nessecary. Modern LCD/LED monitors don't have this issue anymore but apply gamma correction anyway. (For compatibility reasons? Can this be disabled?) All games have to apply gamma correction? (unsure about that) All textures stored in file formats (.png for example) are essentially stored in SRGB color space (as what we see on the monitor is skewed due to gamma correction. So the pixel information is the same, the percieved colors are just wrong.) This makes textures loaded into the GL_RGB format non linear, thus all lighting calculations are wrong You have to always use the GL_SRGB format to gamma correct/linearise textures which are in SRGB format  
      Now, i'm kinda confused how to proceed with applying gamma correction in OpenGL.
      First of, how can i check if my Monitor is applying gamma correction? I noticed in my monitor settings that my color format is set to "RGB" (can't modify it though.) I'm connected to my PC via a HDMI cable. I'm also using the full RGB range (0-255, not the 16 to ~240 range)
      What i tried to do is to apply a gamma correction shader shown in the tutorial above which looks essentially like this: (it's a postprocess shader which is applied at the end of the renderpipeline)
      vec3 gammaCorrection(vec3 color){ // gamma correction color = pow(color, vec3(1.0/2.2)); return color; } void main() { vec3 color; vec3 tex = texture2D(texture_diffuse, vTexcoord).rgb; color = gammaCorrection(tex); outputF = vec4(color,1.0f); } The results look like this:
      No gamma correction:
      With gamma correction:
      The colors in the gamma corrected image look really wased out. (To the point that it's damn ugly. As if someone overlayed a white half transparent texture. I want the colors to pop.)
      Do i have to change the textures from GL_RGB to GL_SRGB in order to gamma correct them in addition to applying the post process gamma correction shader? Do i have to do the same thing with all FBOs? Or is this washed out look the intended behaviour?
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