In working on the trajectory planner and kinematics, I've noticed that
there is a lot of translation between the EmcPose struct and array-like
data. Examples include (in master):
- emc/kinematics/gantrykins.c:32
- emc/kinematics/5axiskins.c:39
- emc/kinematics/tp.c (multiple)
Could EmcPose be replaced with a flatter structure like this?
typdef struct {
double axis[9];
unsigned int size;
} EmcPose
There are a few reasons to use this "flat" structure:
1. *Conceptual*: If we want to generalize LinuxCNC to other kinematics,
then it makes less sense to treat XYZ as a special subset of the axes. A
simple array of axes is easier to work with for complex kinematics.
2. *Implementation:* It's easier to do operations on the whole pose
(just iterate over the array)
3. *Efficiency:* We can set the "size" to the actual number of axes, and
only iterate up to that size during operations. This way we can "skip" axes
that are always zero anyway.
4. *Cruft:* Eliminate much of the translation between datatypes in TP,
motion, and others.
Obviously, the task wouldn't be easy or quick, as there are at least 190
references to EmcPose in the current master. If the effort / inertia wasn't
a factor, though, are there other reasons that EmcPose needs to be defined
the way it is?
I'm planning on using a data structure similar to this to implement
blending arcs, so the groundwork will be there to do such a conversion. I
see this as a long-term goal rather than an immediate necessity, but if
there's popular support, I'd be happy to take in on eventually.
Thanks,
-Rob
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