touch object GLKIT or OpenGL any functions? - ios

Question

I am looking for a description to touch my OpenGL object or get an Event if I touch it.
Have the GLKit or OpenGL ES some functions to use?
Or I have to calculate the position of my Object and have to compare it with the coordination ob my Touch?

Answer 1

There is no built in one, but here is a ported version of the gluProject function that will put a point from your object in screen coordinates, so you can see if your touch is near that point:
GLKVector3 gluProject(GLKVector3 position,
GLKMatrix4 projMatrix,
GLKMatrix4 modelMatrix,
CGRect viewport
)
{
GLKVector4 in;
GLKVector4 out;
in = GLKVector4Make(position.x, position.y, position.z, 1.0);
out = GLKMatrix4MultiplyVector4(modelMatrix, in);
in = GLKMatrix4MultiplyVector4(projMatrix, out);
if (in.w == 0.0) NSLog(#"W = 0 in project function\n");
in.x /= in.w;
in.y /= in.w;
in.z /= in.w;
/* Map x, y and z to range 0-1 */
in.x = in.x * 0.5 + 0.5;
in.y = in.y * 0.5 + 0.5;
in.z = in.z * 0.5 + 0.5;
/* Map x,y to viewport */
in.x = in.x * (viewport.size.width) + viewport.origin.x;
in.y = in.y * (viewport.size.height) + viewport.origin.y;
return GLKVector3Make(in.x, in.y, in.z);
}
- (GLKVector2) getScreenCoordOfPoint {
GLKVector3 out = gluProject(self.point, modelMatrix, projMatrix, view.frame);
GLKVector2 point = GLKVector2Make(out.x, view.frame.size.height - out.y);
return point;
}