Converting OpenGL coordinates to lower UIView (and UIImagePickerController)
- by John Qualis
I am new to OpenGL on the iPhone.
I am developing an iPhone app similar to a barcode reader but with an extra OpenGL layer. The bottommost layer is UIImagePickerController, then I use UIView on top and draw a rectangle at certain coordinates on the iPhone screen. So far everything is OK. Then I am trying to draw an OpenGL 3-D model in that rectangle. I am able to load a 3-D model in the iPhone based on this code here - http://iphonedevelopment.blogspot.com/2008/12/start-of-wavefront-obj-file-loader.html
I am not able to transform the coordinates of the rectangle into OpenGL coordinates. Appreciate any help.
Do I need to use a matrix to translate the currentPosition of the 3-D model so it is drawn within myRect? The code is given below.
-(void)setupView:(GLView*)view
{
const GLfloat zNear = 0.01, zFar = 1000.0, fieldOfView = 45.0;
GLfloat size;
glEnable(GL_DEPTH_TEST);
glMatrixMode(GL_PROJECTION);
size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0);
CGRect rect = view.bounds;
glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size /
(rect.size.width / rect.size.height), zNear, zFar);
glViewport(0, 0, rect.size.width, rect.size.height);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
NSString *path = [[NSBundle mainBundle] pathForResource:@"plane" ofType:@"obj"];
OpenGLWaveFrontObject *theObject = [[OpenGLWaveFrontObject alloc] initWithPath:path];
Vertex3D position;
position.z = -8.0;
position.y = 3.0;
position.x = 2.0;
theObject.currentPosition = position;
self.plane = theObject;
[theObject release];
}
- (void)drawView:(GLView*)view;
{
static GLfloat rotation = 0.0;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glColor4f(0.0, 0.5, 1.0, 1.0);
// the coordinates of the rectangle are
// myRect.x, myRect.y, myRect.width, myRect.height
// Do I need to use a matrix to translate the currentPosition of the
// 3-D model so it is drawn within myRect?
//glOrthof(-160.0f, 160.0f, -240.0f, 240.0f, -1.0f, 1.0f);
[plane drawSelf];
}
