* Normalize the junction direction vector over XYZE
calc_vmax_junction_deviation() treats the dot product of two jd_unit_vec as a
cosine, but the vectors were scaled by 1 / block.distance, which is the XYZ
length. On an extruding move the E component then pushes the 4D norm above 1 and
the dot product below -1, so the corner reads as straighter than it is and is
planned too fast -- the more so the higher the flow. Measured on a 6 degree
corner at scv 5: 86.9mm/s with no extrusion, 94.4mm/s at 0.029mm/mm, 150.0mm/s
at 0.1mm/mm.
Neither firmware does that. Marlin normalizes over XYZE for any extruding move
(planner.cpp: `if (... || esteps > 0) normalize_junction_vector(unit_vec)`) and
Klipper leaves E out of the cosine entirely, dotting only axes_r[0..2]
(toolhead.py::Move.calc_junction). Normalizing satisfies both: with E normalized
in, the cosine differs from the XYZ-only one by ~1e-5 at printing flow rates.
This is a deliberate divergence from PrusaSlicer, which still scales by
1 / distance -- it carries an older Marlin's behaviour.
Travel moves are unaffected, their vector was already unit length.
Reported by Copilot in review of #15304.
* Test that extrusion rate does not change corner planning
The junction deviation tests were all travel-only, which is exactly why the E
component of the junction vector went unchecked. Cover it: the same corner has
to be planned the same whether nothing, an ordinary 0.42 x 0.2 line, or a fat
large-nozzle line is extruded through it, on both Klipper and Marlin 2.
Reported by Copilot in review of #15304.
* 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.
The time estimator's speed/acceleration limits were indexed by time
mode only, reading slot 0 of the per-(extruder x volume-type) arrays
the multi-extruder profiles already carry (H2C 0.4: 8 entries, H2D
0.4: 10). Every move was therefore modelled with the first machine
slot's limits regardless of which nozzle variant was printing -
estimation fidelity only, since emitted feedrates/accelerations are
decided on the slicing side.
Now the estimator resolves the machine slot of the nozzle currently
mounted in the active extruder: the nozzle grouping context is handed
to the processor BEFORE the streaming replay (new member + setter -
deliberately separate from the post-stream result-field handover that
gates the richer change-time model, whose timing is unchanged), the
occupancy recorder is populated on every filament change (bookkeeping
decoupled from the gated time model; recorder writes have no time
effect), and get_machine_config_idx maps (volume type x extruder type
x extruder) to the slot via the printer's variant layout, newly
carried on the processor result. The feedrate/acceleration getters
gain a slot parameter indexing [slot*2 + mode]; jerk and the
print/travel/retract accelerations stay mode-only. Reloaded sliced
projects re-estimate with the result's saved grouping context;
imported bare g-code degrades to slot 0 - the historical read.
M201/M203 write the parsed value into EVERY slot's mode entry (a
firmware envelope change is global), which keeps per-slot reads in
lockstep with the mode-only reads they replace: the fleet emits
envelope lines before any motion, so estimates - hence the estimated
time header, M73 lines, and every other byte - are unchanged (20/20
pinned-slice byte gate bit-identical, incl. the sequential repro
sliced twice). Fidelity improves where envelope emission is off or a
migrating per-layer plan moves filaments across variants.
Tests: a stub-driven processor case proving the slot follows the
active nozzle through the exact production path (T..H.. commands,
fallback recorder bookkeeping, 4x time ratio on the slow variant),
that emitted M201/M203 reach every slot, and that a missing context
degrades to slot 0. Suites green (libslic3r 48998/169, fff_print
667/62).
