Projected coordinates of a 3D CALayer

There's no explicit method to get projected coordinates of a 3D CALayer, but you can use convertRect:fromLayer to almost get them. Thanks to Simon Fraser on the Quartz ML for that.

Suppose you have layers setup like that :


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.

I only tested axis aligned layers. If you want coordinates from a rotated layer, you might try convertPoint:fromLayer to convert each layer point.

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