Transform OpenGL coordinates to lower UIView coordinates

Posted by John Qualis on Stack Overflow See other posts from Stack Overflow or by John Qualis
Published on 2010-03-15T10:28:38Z Indexed on 2010/03/15 14:49 UTC
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I am new to OpenGL over 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 co-ordinates 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 -

I am not able to transform the co-ordinates of the rectangle into OpenGL co-ordinates. 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.. Appreciate any help/pointers in this regards.


  • (void)drawView:(GLView*)view
    static GLfloat rotation = 0.0;
    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 a transform matrix here?
    //glOrthof(-160.0f, 160.0f, -240.0f, 240.0f, -1.0f, 1.0f);
    [plane drawSelf];
    .... }

const GLfloat zNear = 0.01, zFar = 1000.0, fieldOfView = 45.0;
GLfloat size;
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);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

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