Reputation: 2625
Here is my picking code
public static void pick(GL11 gl){
int[] viewport = new int[4];
ByteBuffer pixel = ByteBuffer.allocateDirect(3).order(ByteOrder.nativeOrder());
mColourR = BaseObject.getColourR();
mColourG = BaseObject.getColourG();
mColourB = BaseObject.getColourB();
x = MGLSurfaceView.X();
y = MGLSurfaceView.Y();
gl.glGetIntegerv(GL11.GL_VIEWPORT,viewport,0);
gl.glReadPixels((int)x, (int)(viewport[3] - y), 1, 1, GL11.GL_RGB, GL11.GL_UNSIGNED_BYTE, pixel);
Log.d(TAG, String.valueOf(gl.glGetError()));
R = pixel.get(0);
G = pixel.get(1);
B = pixel.get(2);
Log.d(TAG, "Colour:" + pixel.get(0) + " " + pixel.get(1) + " " + pixel.get(2));
if (R == mColourR && G == mColourG && B == mColourB){
match = true;
}else{
match = false;
}
Log.d(TAG, String.valueOf(match));
Log.d(TAG, String.valueOf(viewport[0]) + "," + String.valueOf(viewport[1]) + "," + String.valueOf(viewport[2]) + "," + String.valueOf(viewport[3]));
}
Sorry about the mess. Anyway this code always seems to return (0,0,0) regardless of where I click. I have a red square, a green, square and a blue background for testing purposes and this method gets called every time one of the squares is drawn and the screen has been pressed like so
BaseObject.newColour();
mColourR = BaseObject.getColourR();
mColourG = BaseObject.getColourG();
mColourB = BaseObject.getColourB();
gl.glPushMatrix();
gl.glColor4f(mColourR, mColourG, mColourB, 0.0f);
gl.glTranslatef(x1, y1, 0);
square.draw(gl);
gl.glPopMatrix();
ColourPicking.pick((GL11)gl);
match = ColourPicking.getMatch();
if (match == true){
x1 = (float) Math.floor(Math.random()*9);
y1 = (float) Math.floor(Math.random()*7);
match = false;
}
Even though there is no black space on screen I always get black values so I'm pretty sure its not just a precision problem. I have a log tag in there that returns the viewport values and they're fine, I've also checked my x y coordinates and they seem legit the only thing I have to go on is the 1282 error code.
Does anyone have any idea what this could be?
EDIT:
Right we know that the problem is coming from the read pixel function because I put glGetError() before and after the function and it came back
Before: 0
After: 1282
Getting rid of scaling didn't help but that was a long shot
I've changed the Buffer to a FloatBuffer and now I'm getting back (0.0, 0.0, 0.0) instead of (0, 0, 0) not much of a victory I know. I also noticed that the error is now 1280 (GL_INVALID_ENUM). I don't know if this is a step foreward. Does anybody know how to fix this error if not error 1282.
Upvotes: 2
Views: 3687
Reputation: 13348
When you're getting GL_INVALID_ENUM, that's probably because you're passing GL_RGB as format parameter to glReadPixels. According to the Khronos documentation for glReadPixels, there are only 2 possible pairs of values for format and type:
I ran into the same problem recently, and using GL_RGBA fixed it for me.
Upvotes: 10