diff --git a/Marlin/src/gcode/motion/G2_G3.cpp b/Marlin/src/gcode/motion/G2_G3.cpp index c713877a0e6a..b920e2307336 100644 --- a/Marlin/src/gcode/motion/G2_G3.cpp +++ b/Marlin/src/gcode/motion/G2_G3.cpp @@ -77,16 +77,21 @@ void plan_arc( rt_Y = cart[q_axis] - center_Q, start_L = current_position[l_axis]; - // CCW angle of rotation between position and target from the circle center. Only one atan2() trig computation required. + // Angle of rotation between position and target from the circle center. float angular_travel = ATAN2(rvec.a * rt_Y - rvec.b * rt_X, rvec.a * rt_X + rvec.b * rt_Y); - if (angular_travel < 0) angular_travel += RADIANS(360); + + // Make sure angular travel over 180 degrees goes the other way around. + switch (((angular_travel < 0) << 1) + clockwise) { + case 1: angular_travel -= RADIANS(360); break; // Positive but CW? Reverse direction. + case 2: angular_travel += RADIANS(360); break; // Negative but CCW? Reverse direction. + } + #ifdef MIN_ARC_SEGMENTS - uint16_t min_segments = CEIL((MIN_ARC_SEGMENTS) * (angular_travel / RADIANS(360))); + uint16_t min_segments = CEIL((MIN_ARC_SEGMENTS) * ABS(angular_travel) / RADIANS(360)); NOLESS(min_segments, 1U); #else constexpr uint16_t min_segments = 1; #endif - if (clockwise) angular_travel -= RADIANS(360); // Make a circle if the angular rotation is 0 and the target is current position if (NEAR_ZERO(angular_travel) && NEAR(current_position[p_axis], cart[p_axis]) && NEAR(current_position[q_axis], cart[q_axis])) {