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Time estimator fixes (#15304)

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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.
This commit is contained in:
Ian Bassi
2026-08-20 09:16:02 -03:00
committed by GitHub
parent dc75ce6811
commit aaa8e98bb0
3 changed files with 307 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/libslic3r/GCode/GCodeProcessor.cpp
+129 -20
View File
@@ -298,6 +298,7 @@ void GCodeProcessor::TimeMachine::State::reset()
//BBS
enter_direction = { 0.0f, 0.0f, 0.0f };
exit_direction = { 0.0f, 0.0f, 0.0f };
jd_unit_vec = { 0.0f, 0.0f, 0.0f, 0.0f };
}
void GCodeProcessor::TimeMachine::CustomGCodeTime::reset()
@@ -5036,6 +5037,10 @@ void GCodeProcessor::process_G1(const std::array<std::optional<double>, 4>& axes
if (!is_extrusion_only_move(delta_pos))
curr.enter_direction = curr.enter_direction / norm;
curr.exit_direction = curr.enter_direction;
curr.jd_unit_vec = Vec4f(static_cast<float>(delta_pos[X]) * inv_distance,
static_cast<float>(delta_pos[Y]) * inv_distance,
static_cast<float>(delta_pos[Z]) * inv_distance,
static_cast<float>(delta_pos[E]) * inv_distance);
TimeBlock block;
block.move_type = type;
@@ -5118,22 +5123,32 @@ void GCodeProcessor::process_G1(const std::array<std::optional<double>, 4>& axes
block.acceleration = acceleration;
// calculates block exit feedrate
curr.safe_feedrate = block.feedrate_profile.cruise;
static const float PREVIOUS_FEEDRATE_THRESHOLD = 0.0001f;
const bool has_prev_move = !blocks.empty() && prev.feedrate > PREVIOUS_FEEDRATE_THRESHOLD;
for (unsigned char a = X; a <= E; ++a) {
float axis_max_jerk = get_axis_max_jerk(static_cast<PrintEstimatedStatistics::ETimeMode>(i), static_cast<Axis>(a));
if (curr.abs_axis_feedrate[a] > axis_max_jerk)
curr.safe_feedrate = std::min(curr.safe_feedrate, axis_max_jerk);
// Orca: junction deviation where the firmware uses it (Klipper always, Marlin 2 with M205 J).
// Negative leaves the classic jerk path below unchanged.
const float vmax_junction_jd = calc_vmax_junction_deviation(block, prev, curr, has_prev_move,
static_cast<PrintEstimatedStatistics::ETimeMode>(i));
const bool use_junction_deviation = vmax_junction_jd >= 0.0f;
// calculates block exit feedrate. Junction deviation has no per axis jerk floor, so a move is
// free to start from rest.
curr.safe_feedrate = use_junction_deviation ? 0.0f : block.feedrate_profile.cruise;
if (!use_junction_deviation) {
for (unsigned char a = X; a <= E; ++a) {
float axis_max_jerk = get_axis_max_jerk(static_cast<PrintEstimatedStatistics::ETimeMode>(i), static_cast<Axis>(a));
if (curr.abs_axis_feedrate[a] > axis_max_jerk)
curr.safe_feedrate = std::min(curr.safe_feedrate, axis_max_jerk);
}
}
block.feedrate_profile.exit = curr.safe_feedrate;
static const float PREVIOUS_FEEDRATE_THRESHOLD = 0.0001f;
// calculates block entry feedrate
float vmax_junction = curr.safe_feedrate;
if (!blocks.empty() && prev.feedrate > PREVIOUS_FEEDRATE_THRESHOLD) {
float vmax_junction = use_junction_deviation ? vmax_junction_jd : curr.safe_feedrate;
if (!use_junction_deviation && has_prev_move) {
bool prev_speed_larger = prev.feedrate > block.feedrate_profile.cruise;
float smaller_speed_factor = prev_speed_larger ? (block.feedrate_profile.cruise / prev.feedrate) : (prev.feedrate / block.feedrate_profile.cruise);
// Pick the smaller of the nominal speeds. Higher speed shall not be achieved at the junction during coasting.
@@ -5400,6 +5415,10 @@ void GCodeProcessor::process_VG1(const GCodeReader::GCodeLine& line)
if (!is_extrusion_only_move(delta_pos))
curr.enter_direction = curr.enter_direction / norm;
curr.exit_direction = curr.enter_direction;
curr.jd_unit_vec = Vec4f(static_cast<float>(delta_pos[X]) * inv_distance,
static_cast<float>(delta_pos[Y]) * inv_distance,
static_cast<float>(delta_pos[Z]) * inv_distance,
static_cast<float>(delta_pos[E]) * inv_distance);
TimeBlock block;
block.move_type = type;
@@ -5480,22 +5499,32 @@ void GCodeProcessor::process_VG1(const GCodeReader::GCodeLine& line)
block.acceleration = acceleration;
// calculates block exit feedrate
curr.safe_feedrate = block.feedrate_profile.cruise;
static const float PREVIOUS_FEEDRATE_THRESHOLD = 0.0001f;
const bool has_prev_move = !blocks.empty() && prev.feedrate > PREVIOUS_FEEDRATE_THRESHOLD;
for (unsigned char a = X; a <= E; ++a) {
float axis_max_jerk = get_axis_max_jerk(static_cast<PrintEstimatedStatistics::ETimeMode>(i), static_cast<Axis>(a));
if (curr.abs_axis_feedrate[a] > axis_max_jerk)
curr.safe_feedrate = std::min(curr.safe_feedrate, axis_max_jerk);
// Orca: junction deviation where the firmware uses it (Klipper always, Marlin 2 with M205 J).
// Negative leaves the classic jerk path below unchanged.
const float vmax_junction_jd = calc_vmax_junction_deviation(block, prev, curr, has_prev_move,
static_cast<PrintEstimatedStatistics::ETimeMode>(i));
const bool use_junction_deviation = vmax_junction_jd >= 0.0f;
// calculates block exit feedrate. Junction deviation has no per axis jerk floor, so a move is
// free to start from rest.
curr.safe_feedrate = use_junction_deviation ? 0.0f : block.feedrate_profile.cruise;
if (!use_junction_deviation) {
for (unsigned char a = X; a <= E; ++a) {
float axis_max_jerk = get_axis_max_jerk(static_cast<PrintEstimatedStatistics::ETimeMode>(i), static_cast<Axis>(a));
if (curr.abs_axis_feedrate[a] > axis_max_jerk)
curr.safe_feedrate = std::min(curr.safe_feedrate, axis_max_jerk);
}
}
block.feedrate_profile.exit = curr.safe_feedrate;
static const float PREVIOUS_FEEDRATE_THRESHOLD = 0.0001f;
// calculates block entry feedrate
float vmax_junction = curr.safe_feedrate;
if (!blocks.empty() && prev.feedrate > PREVIOUS_FEEDRATE_THRESHOLD) {
float vmax_junction = use_junction_deviation ? vmax_junction_jd : curr.safe_feedrate;
if (!use_junction_deviation && has_prev_move) {
bool prev_speed_larger = prev.feedrate > block.feedrate_profile.cruise;
float smaller_speed_factor = prev_speed_larger ? (block.feedrate_profile.cruise / prev.feedrate) : (prev.feedrate / block.feedrate_profile.cruise);
// Pick the smaller of the nominal speeds. Higher speed shall not be achieved at the junction during coasting.
@@ -7168,6 +7197,86 @@ float GCodeProcessor::get_axis_max_jerk_with_jd(PrintEstimatedStatistics::ETimeM
return get_axis_max_jerk_with_jd(mode, axis, get_acceleration(mode));
}
float GCodeProcessor::get_junction_deviation(PrintEstimatedStatistics::ETimeMode mode, float acceleration) const
{
const size_t id = static_cast<size_t>(mode);
// Klipper has no classic jerk: jd = scv^2 * (sqrt(2) - 1) / max_accel
// (toolhead.py::_calc_junction_deviation). Passing the block acceleration back in makes it cancel
// in calc_vmax_junction_deviation(), leaving the identity v == scv at a 90 degree corner.
if (m_flavor == gcfKlipper) {
// machine_max_jerk_x holds the square corner velocity; process_SET_VELOCITY_LIMIT() writes it.
const float scv = get_option_value(m_time_processor.machine_limits.machine_max_jerk_x, id);
if (scv <= 0.0f || acceleration <= 0.0f)
return 0.0f;
return sqr(scv) * (std::sqrt(2.0f) - 1.0f) / acceleration;
}
// Marlin 2 plans with junction deviation only when M205 J > 0; classic jerk leaves it at 0.
if (m_flavor == gcfMarlinFirmware)
return get_option_value(m_time_processor.machine_limits.machine_max_junction_deviation, id);
return 0.0f;
}
float GCodeProcessor::calc_junction_acceleration(const TimeBlock& block, const Vec4f& junction_unit_vec,
PrintEstimatedStatistics::ETimeMode mode) const
{
float junction_acceleration = block.acceleration;
for (unsigned char a = X; a <= E; ++a) {
if (junction_unit_vec[a] == 0.0f)
continue;
const float axis_max_acceleration = get_axis_max_acceleration(mode, static_cast<Axis>(a), m_machine_config_idx);
if (axis_max_acceleration > 0.0f)
junction_acceleration = std::min(junction_acceleration, std::abs(axis_max_acceleration / junction_unit_vec[a]));
}
return junction_acceleration;
}
// Ported from PrusaSlicer (src/libslic3r/GCode/GCodeProcessor.cpp).
float GCodeProcessor::calc_vmax_junction_deviation(const TimeBlock& block, const TimeMachine::State& prev,
const TimeMachine::State& curr, bool has_prev_move,
PrintEstimatedStatistics::ETimeMode mode) const
{
const float junction_deviation = get_junction_deviation(mode, block.acceleration);
if (junction_deviation <= 0.0f)
return -1.0f; // classic jerk machine, the caller keeps its own computation
if (!has_prev_move)
return 0.0f; // starts from rest, the planner raises this on the reverse pass
// -1 for a straight continuation, +1 for a full reversal. Half angle identity, no acos()/sin().
float junction_cos_theta = (-prev.jd_unit_vec).dot(curr.jd_unit_vec);
if (junction_cos_theta > 0.999999f)
return 0.0f; // the path doubles back, the machine has to stop
junction_cos_theta = std::max(junction_cos_theta, -0.999999f); // guards the division below
const float sin_theta_d2 = std::sqrt(0.5f * (1.0f - junction_cos_theta)); // always positive
const Vec4f junction_vec = curr.jd_unit_vec - prev.jd_unit_vec;
const float junction_vec_norm = junction_vec.norm();
const Vec4f junction_unit_vec = (junction_vec_norm > 0.0f) ? Vec4f(junction_vec / junction_vec_norm)
: Vec4f(0.0f, 0.0f, 0.0f, 0.0f);
const float junction_acceleration = calc_junction_acceleration(block, junction_unit_vec, mode);
float vmax_junction_sqr = (junction_acceleration * junction_deviation * sin_theta_d2) / (1.0f - sin_theta_d2);
// Marlin's JD_HANDLE_SMALL_SEGMENTS: a short move through a shallow corner is treated as an arc and
// capped by the centripetal acceleration it needs. Klipper has no equivalent.
if (m_flavor != gcfKlipper && block.distance < 1.0f && junction_cos_theta < -0.7071067812f) {
// Fast acos(-t), max. error +-0.033rad. MinMax polynomial by W. Randolph Franklin:
// https://wrf.ecse.rpi.edu/Research/Short_Notes/arcsin/onlyelem.html
const float neg = junction_cos_theta < 0.0f ? -1.0f : 1.0f;
const float t = neg * junction_cos_theta;
const float asinx = 0.032843707f + t * (-1.451838349f + t * (29.66153956f + t * (-131.1123477f +
t * (262.8130562f + t * (-242.7199627f + t * (84.31466202f))))));
const float junction_theta = float(0.5 * M_PI) + neg * asinx; // acos(-t), bottoms out at 0.033
vmax_junction_sqr = std::min(vmax_junction_sqr, (block.distance * junction_acceleration) / junction_theta);
}
// Never faster than either of the two moves the junction joins.
vmax_junction_sqr = std::min(vmax_junction_sqr, std::min(sqr(block.feedrate_profile.cruise), sqr(prev.feedrate)));
return std::sqrt(vmax_junction_sqr);
}
float GCodeProcessor::get_axis_max_jerk(PrintEstimatedStatistics::ETimeMode mode, Axis axis) const
{
const size_t id = static_cast<size_t>(mode);