Andrew Poelstra wrote:
On Tue, Oct 12, 2010 at 10:12:41PM +0200, Armin Faltl wrote:
Btw. while being a different topic, how about getting rid of the lefthanded
coordinate system, when all numeric computations have to be checked
anyway? This should make the cs consistent with trigonometric functions.
What does lefthanded coordinate system mean?
It means, that positive coordinate axes can be generated as follows:
looking from Z+ to the center X+ moves into Y+ by a clockwise
rotation (for lefthand). Z+ is your extended thumb, then form your
fingers to a hook;
the finger tips point into the direction of rotation around the thumb.
With cyclic permutation look along:
Z+: X - Y
X+: Y - Z
Y+: Z - X
A lefthanded coordnate system is the mirror image of a righthanded one,
the later being the norm for mathematical formulations, esp. vector
notation of rotation.
E.g. in polar coordinates P = P(r, phi) the angle phi has to be measured
counterclockwise from the X-axis to make the transformation to
cartesian coordinates look like:
P = P(x, y) = P(r*cos(phi), r*sin(phi))
with X+ pointing right an Y+ pointing up (and Z+ pointing out of screen).
This is a convention. One can argue, to define the the sense of rotation
clockwise
and have Y+ look downward, but this is against the mathematical standard
and pcb is the only CAD program I know of, that does like this.
It's incompatible with any CAM file format, plotter language, OpenGL etc.
Many raster devices and -image formats are lefthanded, probably the
reason, why pcb is.
Sorry for (partly) repeating myself.
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