auto extrusion for arcs too

README.md

@@ -3,6 +3,5 @@ G-code generator for Marlin printers.
 Inspired by [Full Control GCODE](http://fullcontrolgcode.com/).
 
 ## Planned features
-- create g-code based on mathematical functions/generators
 - cleaner interfacing for absolute movements
 

examples/circlegrid.py

@@ -15,7 +15,7 @@
     g.travel((0, 20, 0))
     for j in range(3):
         g.travel((20, 0, 0))
-        g.draw_arc(0, -10, e=5)
+        g.draw_arc(0, -10)
     g.travel((-60, 0, 0))
 
 g.set_tool_temp(0)

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = gcodepy
-version = 0.0.1
+version = 0.1.0
 author = Rahul Menon
 author_email = [email protected]
 description = Tool to generate g-code for Marlin based printers

src/gcodepy/gcode.py

@@ -1,9 +1,11 @@
 from typing import Callable, Tuple, Union
+import math
 from . import util
 
-# circumference calcs for arcs
+# TODO:
 # minimize feedrate output
 # draw absolute
+# catch more invalid inputs
 class Gcode:
     def __init__(
         self,
@@ -92,9 +94,14 @@ def travel(self, delta: Tuple[float, float, float], feedrate: int = 2400):
         self.pos[0] += delta[0]
         self.pos[1] += delta[1]
         self.pos[2] += delta[2]
-        self.file.write(
-            f"G0 F{feedrate} X{self.pos[0]} Y{self.pos[1]} Z{self.pos[2]}\n"
-        )
+        out = f"G0 F{feedrate}"
+        if delta[0] != 0.0:
+            out += f" X{self.pos[0]}"
+        if delta[1] != 0.0:
+            out += f" Y{self.pos[1]}"
+        if delta[2] != 0.0:
+            out += f" Z{self.pos[2]}"
+        self.file.write(out + "\n")
 
     def travel_arc(
         self,
@@ -139,9 +146,15 @@ def draw(
         self.pos[1] += delta[1]
         self.pos[2] += delta[2]
         self.e += e
-        self.file.write(
-            f"G1 F{feedrate} X{self.pos[0]} Y{self.pos[1]} Z{self.pos[2]} E{self.e}\n"
-        )
+        out = f"G1 F{feedrate}"
+        if delta[0] != 0.0:
+            out += f" X{self.pos[0]}"
+        if delta[1] != 0.0:
+            out += f" Y{self.pos[1]}"
+        if delta[2] != 0.0:
+            out += f" Z{self.pos[2]}"
+        out += f" E{e}"
+        self.file.write(out + "\n")
 
     def draw_arc(
         self,
@@ -154,7 +167,7 @@ def draw_arc(
     ):
         if e is None:
             e = self.extrusion_length_calculator(
-                util.dist(delta),  # REPLACE
+                util.arclen((i, j), delta[:2], clockwise),
                 self.line_width,
                 self.layer_height,
                 self.filament_width,
@@ -182,9 +195,19 @@ def draw_arc_r(
         clockwise: bool = True,
         feedrate: int = 2400,
     ):
+        if r == 0 or r is None:
+            raise ValueError("Radius r cannot be 0 or None.")
         if e is None:
+            d2 = (delta[0] / 2, delta[1] / 2)
+            m = -1 if clockwise ^ (r < 0) else 1
+            l = util.dist(d2)
+            h2 = (r - l) * (r + l)
+            h = 0 if h2 < 0 else math.sqrt(h2)
+            s = (-d2[1], d2[0])
+            s = [s[i] / l * m * h for i in range(2)]
+            center = tuple(d2[i] + s[i] for i in range(2))
             e = self.extrusion_length_calculator(
-                util.dist(delta),  # REPLACE
+                util.arclen(center, delta[:2], clockwise),
                 self.line_width,
                 self.layer_height,
                 self.filament_width,

src/gcodepy/util.py

@@ -1,11 +1,35 @@
 import math
-from typing import Tuple
+from typing import Iterable, Tuple
 
 
-def dist(delta: Tuple[float, float, float]) -> float:
+def dist(delta: Iterable[float]) -> float:
     return math.sqrt(sum(i ** 2 for i in delta))
 
 
+def arclen(
+    center: Tuple[float, float], other: Tuple[float, float], clockwise: bool
+) -> float:
+    radius = dist(center)
+    if other == (0.0, 0.0):
+        return math.pi * radius ** 2
+
+    # using formula theta = atan2(||u x v||, u . v)
+    rvec = tuple(-i for i in center)
+    rt = tuple(other[i] - center[i] for i in range(2))
+    uxv = rvec[0] * rt[1] - rvec[1] * rt[0]
+    udv = rvec[0] * rt[0] + rvec[1] * rt[1]
+    angle = math.atan2(uxv, udv)
+    if abs(angle) < 1e-6:
+        return 0
+
+    if clockwise and angle > 0:
+        angle = 2 * math.pi - angle
+    elif not clockwise and angle < 0:
+        angle += 2 * math.pi
+
+    return angle * radius
+
+
 def calculate_extrusion_length(
     path_length: float,
     line_width: float,