I'm wanting to draw a polygon around a layer. I want the polygon to
be 1 pixel wide regardless of the transformations applied to the
layer. As such a border/borderWidth solution won't work because
it'll be scaled if the layer is scaled. So I've computed the scaled
and rotated coordinates of said layer by walking up the layer tree and
applying the affine transforms top-down to each of the four points
making up the original rectangle of the layer. This gives me what I
want - until I do rotation with sublayerTransforms.
In an ideal world I'd like to know if there is also a way to apply a
CATransform3D to a point.
For example, in order to compute the translation, scale and
rotation(z) of a given point from the original rectangle I need do only:
point = CGPointApplyAffineTransform(point, [layer affineTransform]);
However there doesn't seem to be an equivalent function for
CATransform3D transforms.
Any suggestions? I've spent the entire day reading about perspective
transformations and projections (lots of matrix math). I'm happy (as
happy as someone that's not done this stuff for many years can be) to
go down this path if it's absolutely required, but was wondering if
anyone knew of a simpler way (rather than reinventing the wheel) of
applying the same (or close enough - similar) math that CA/OpenGL is
applying to the sublayerTransform a matrix.
To be clear, I'm talking specifically about computing the final value
of a point in a layer given that I've set the m34 field of the
sublayerTransform in order to achieve a perspective effect (ala:
CovertFlow).
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