...and pcb is the only CAD program I know of, that does like this I've run across other PC layout tools which do this. Mechanical CAD tools usually have (by default) Y+ pointing up, but for some reason PC design tools occasionally have Y+ facing down. I don't remember any of these tools justifying their (less common) choice of convention however. :) Joe T
On Wed, Oct 13, 2010 at 3:35 AM, Armin Faltl <[1]armin.fa...@aon.at> wrote: 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. _______________________________________________ geda-user mailing list [2]geda-u...@moria.seul.org [3]http://www.seul.org/cgi-bin/mailman/listinfo/geda-user References 1. mailto:armin.fa...@aon.at 2. mailto:geda-user@moria.seul.org 3. http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
_______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user