Christian Froeschlin <chr### [at] chrfrde> wrote:
> As an aside, it was noted that the AOI pattern as well as the slope
> pattern do not react to transformations in an intuitive manner (the
> directional component remains unchanged by the transformation).

  I can understand why it would be desirable for the slope pattern to
be transformed regularly with the texture transformations because the
slope pattern is not view-dependent, but local to the object space.
(For example, if you apply a slope pattern to a heightfield to eg.
make a snow/ground texture, you probably want it to look the same
even if you rotate the heightfield, as if the slope pattern was a
regular texture applied to the heightfield.)

  However, angle-of-incidence is *by definition* a view-dependent pattern.
In other words, it changes depending on where the object is looked from.
That's the very definition of "angle of incidence".

  Thus I would expect for it to work always the same way regardless of
how the object is transformed. In other words, I expect it to solely
depend on the viewing direction (with respect to the normal of the
surface), not the orientation of the object.

  AOI is used, for example, to simulate a scanning eletron microscope,
which produces a peculiar pattern which depends on the angle of incidence
of the viewing rays. If the object is rotated, I would still expect it
to depend in this angle of incidence in the same way, rather than the
"pattern" rotating with the object is if it was a texture attached to it.

-- 
                                                          - Warp

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