src/emc/rs274ngc/gcodemodule.cc
@@ -24,6 +24,7 @@
#include "interp_return.hh"
#include "canon.hh"
#include "config.h"             // LINELEN
+#include "units.h"

int _task = 0; // control preview behaviour when remapping

@@ -998,11 +999,17 @@ static PyObject *rs274_arc_to_segments(PyObject
*self, PyObject *args) {

    double theta1 = atan2(o[Y]-cy, o[X]-cx);
    double theta2 = atan2(n[Y]-cy, n[X]-cx);
-
-   if(rot < 0) {
-        while(theta2 - theta1 > -CIRCLE_FUZZ) theta2 -= 2*M_PI;
-    } else {
-        while(theta2 - theta1 < CIRCLE_FUZZ) theta2 += 2*M_PI;
 +   /* Issue #1528 1/2/22 andypugh */
 +   /*_posemath checks for small arcs too, but uses config units */
 +   double len = hypot(o[X]-n[X], o[Y]-n[Y]) * (25.4 *
GET_EXTERNAL_LENGTH_UNITS());
    /* If the signs of the angles differ, make them the same to allow
monotonic progress through the arc */
 +   /* If start and end points are nearly identical, then interpret as
a full turn */
  + if(rot < 0) { // CW G2
  +     if (theta1 < theta2) theta2 -= 2*M_PI;
  +      if (len < CART_FUZZ) theta2 -= 2*M_PI;
  +  } else { // CCW G3
  +      if (theta1 > theta2) theta2 += 2*M_PI;
  +      if (len < CART_FUZZ) theta2 += 2*M_PI;
    }

    // if multi-turn, add the right number of full circles
10



src/libnml/posemath/_posemath.c
@@ -1812,6 +1812,7 @@ int pmCircleInit(PmCircle * const circle,
    } else {
        circle->angle = acos(dot);
    }

    /* now angle is in range 0..PI . Check if cross is antiparallel to
       normal. If so, true angle is between PI..2PI. Need to subtract
from
       2PI. */
@@ -1820,8 +1821,10 @@ int pmCircleInit(PmCircle * const circle,
    if (d < 0.0) {
        circle->angle = PM_2_PI - circle->angle;
    }
-
-   if (circle->angle > -(CIRCLE_FUZZ) && circle->angle <
(CIRCLE_FUZZ)) {
 +   /* Issue #1528 24-Jan-2022. Additional test for nearly-
straight   *
  +   * short arcs of very large radius becoming
circles               */
   + pmCartCartDisp(start, end, &d);
   + if (d < CART_FUZZ){
        circle->angle = PM_2_PI;
    }

@@ -1830,6 +1833,9 @@ int pmCircleInit(PmCircle * const circle,
        circle->angle += turn * 2.0 * PM_PI;
    }

   + /* FIXME: some code has an unguarded division by circle->angle */
   +if (circle->angle == 0) circle->angle += CIRCLE_FUZZ;
   +
    //Default to invalid
/* if 0'ed out while not debugging*/
#if 0
1
src/libnml/posemath/posemath.h
@@ -713,6 +713,7 @@ extern "C" {
// FIXME setting this to be an order of magnitude smaller than canon's
shortest
// allowed segment. This is still larger than TP's smallest position,
so it may
// be silently causing trouble.
// andypugh 5/2/22 This seems to be interpreted to be in config units.
#define CART_FUZZ (1.0e-8)
/* how close a cartesian vector's magnitude must be for it to be
considered
   a zero vector */

%
G21
G90
G2 X0 Y0 Z-1 J4 F1000
G2 X0 Y0 Z-2 J4 F1000
G2 X0 Y0 Z-3 J4 F1000
G2 X0 Y0 Z-4 J4 F1000
G0 X0 Y0 Z0
M30
%

    /* FIXME: some code has an unguarded division by circle->angle */
    if (circle->angle == 0) circle->angle += CIRCLE_FUZZ;

    /* FIXME: some code has an unguarded division by circle->angle */
    if (circle->angle == 0) circle->angle += CIRCLE_FUZZ / 2;

    /* FIXME: some code has an unguarded division by circle->angle */
    //if (circle->angle == 0) circle->angle += CIRCLE_FUZZ / 2;