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* Plan corners with junction deviation where the firmware uses it
The time estimator only ever had the classic per-axis jerk model, which limits a
corner by the largest single-axis component of the velocity change. That is
anisotropic: the same corner is allowed sqrt(2) more speed on a diagonal than on
an axis, which paints a four-lobed ripple around every circular wall in the
actual speed and actual flow views, worst on small parts whose walls are made of
short segments.
Klipper has no classic jerk at all and Marlin 2 has none while M205 J is in use;
both plan corners with junction deviation, which sees only the corner angle. Add
that model and use it for those machines:
- Klipper: derived from the square corner velocity, as the firmware does
(jd = scv^2 * (sqrt(2) - 1) / max_accel), reading the scv from
machine_max_jerk_x, where process_SET_VELOCITY_LIMIT() already stores
SQUARE_CORNER_VELOCITY.
- Marlin 2: machine_max_junction_deviation, which was already loaded into the
machine limits but never reached the planner.
- Every other flavor keeps the classic jerk path unchanged.
The model has no per-axis jerk floor, so this also drops the hard slow spot the
estimator drew at the start of every loop from machine_max_jerk_e.
Toolpaths are unaffected: on a full export the only lines that change are M73.
The junction deviation maths, including Marlin's JD_HANDLE_SMALL_SEGMENTS arc
approximation, is ported from PrusaSlicer's src/libslic3r/GCode/GCodeProcessor.cpp.
The Klipper mapping is not in PrusaSlicer, which ignores SET_VELOCITY_LIMIT.
* Add tests for junction deviation corner planning
Cover the three properties the change rests on:
- a right angle on Klipper is planned at exactly the square corner velocity,
the identity that makes the scv to junction deviation mapping correct, and a
shallow corner is planned far faster than per-axis jerk allows;
- junction deviation gives the same speed whatever the corner's orientation,
while classic jerk keeps its sqrt(2) spread, which is the four-lobed ripple;
- machines that do not plan with junction deviation are provably untouched,
including a Marlin 2 printer that has it disabled.
OrcaSlicer tests
Building, running and writing tests is documented on the wiki, under How to Test.
Two files here rather than there, because coding agents only read what is in the repository: