Color Picking Troubles - LWJGL/OpenGL
- by Tom Johnson
I'm attempting to check which object the user is hovering over. While everything seems to be just how I'd think it should be, I'm not able to get the correct color due to the second time I draw (without picking colors). Here is my rendering code:
public void render() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
camera.applyTranslations();
scene.pick();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
camera.applyTranslations();
scene.render();
}
And here is what gets called on each block/tile on "scene.pick()":
public void pick() {
glColor3ub((byte) pickingColor.x, (byte) pickingColor.y, (byte) pickingColor.z);
draw();
glReadBuffer(GL_FRONT);
ByteBuffer buffer = BufferUtils.createByteBuffer(4);
glReadPixels(Mouse.getX(), Mouse.getY(), 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
int r = buffer.get(0) & 0xFF;
int g = buffer.get(1) & 0xFF;
int b = buffer.get(2) & 0xFF;
if(r == pickingColor.x && g == pickingColor.y && b == pickingColor.z) {
hovered = true;
} else {
hovered = false;
}
}
I believe the problem is that in the method of each tile/block called by scene.pick(), it is reading the color from the regular drawing state, after that method is called somehow. I believe this because when I remove the "glReadBuffer(GL_FRONT)" line from the pick method, it seems to almost fix it, but then it will also select blocks behind the one you are hovering as it is not only looking at the front.
If you have any ideas of what to do, please be sure to reply!/
EDIT: Adding scene.render(), tile.render(), and tile.draw()
scene.render:
public void render() {
for(int x = 0; x < tiles.length; x++) {
for(int z = 0; z < tiles.length; z++) {
tiles[x][z].render();
}
}
}
tile.render:
public void render() {
glColor3f(color.x, color.y, color.z);
draw();
if(hovered) {
glColor3f(1, 1, 1);
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
draw();
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
}
}
tile.draw:
public void draw() {
float x = position.x, y = position.y, z = position.z;
//Top
glBegin(GL_QUADS);
glVertex3f(x, y + size, z);
glVertex3f(x + size, y + size, z);
glVertex3f(x + size, y + size, z + size);
glVertex3f(x, y + size, z + size);
glEnd();
//Left
glBegin(GL_QUADS);
glVertex3f(x, y, z);
glVertex3f(x + size, y, z);
glVertex3f(x + size, y + size, z);
glVertex3f(x, y + size, z);
glEnd();
//Right
glBegin(GL_QUADS);
glVertex3f(x + size, y, z);
glVertex3f(x + size, y + size, z);
glVertex3f(x + size, y + size, z + size);
glVertex3f(x + size, y, z + size);
glEnd();
}
(The game is like an isometric game. That's why I only draw 3 faces.)
