Possible to look back/ahead?

[pomeroyb]

Hello! I'm trying to use vpype-gcode with a controller that is expecting commands to tell it to travel to a point and draw a line. Essentially the "point" function is used as a G0 command, and the "line" function is used as a G1 command. The point command is easily solved with "segment_first", but the line command needs to look like the following:

line((start_x, start_y), (end_x, end_y), speed = 4)

Right now my custom profile looks like this:

[gwrite.pewpew]
document_start = ""
segment_first = "point(({x:.4f},{y:.4f}), delay = 0.25, burn = 0)\n"
segment = "line(({x:.4f},{y:.4f}),({x:.4f},{y:.4f}), speed = 4)\n"
document_end = ""
unit = "in"
invert_y = true
info= "This gcode profile is correctly inverted across the y-axis"

The problem is that the segment cannot (as far as I can tell) refer to the coordinates of the previous segment, so I end up making a zero length line at the coordinates of the current segment. Ideally my toml would have the following:

segment = "line(({prev_x:.4f},{prev_y:.4f}),({x:.4f},{y:.4f}), speed = 4)\n"

Is there a way to do this in vpype-gcode or is this outside of the capabilities of the project currently?

[tatarize]

It's outside the current capabilities. Though it could probably be added. There's some entries for dx, dy so if you could use that rather than the actual previous value you'd be in luck.

[abey79]

Well we have last_x/last_y lying around for the computation of dx/dy. Wouldn't it be trivial to just add them to the template variables? Am I missing something?

[tatarize]

Super trivial. It's an oversight it already doesn't work.