PARMANOIR

Suppose you have layers setup like that :

rootLayer
  layerHavingA3DTransform
    layer1
    layer2
    layer3

layer1, layer2, layer3 will be transformed by layerHavingA3DTransform and will appear 3D. To get their projected coordinates, use

CGRect projectedRect = [layer1 convertRect:localRect toLayer:[self layer]];

This will transform localRect, a rect in layer1 coordinates to root layer coordinates. If you want the layer extent, that's -bounds.width/2, -bounds.height/2, bounds.width, bounds.height for the default anchorPoint of (0.5, 0.5). Note that projectedRect is in layer coordinates, not in NSView coordinates. For this case I had manually centered layerHavingA3DTransform in the view and got coordinates reflecting that, going from -size to +size.