2026: OpenSCAD robot and remote, physical joint limits, model in Unity

hardware/openscad/ rebuilds the broken Fusion models as OpenSCAD:
body (top/bottom plate, standoffs, battery bay, switch), legs (coxa
bracket, femur link, tibia, horn adapters, TPU socks, servo cables),
the whole robot, and the remote (shell, lid, Nextion 3.5", JH-D400X-R4
sticks, 18650 UPS board, IMU, Teensy 4.0, USB-C breakout). Every part
was checked by slicing against the original STEP solids; the original's
bugs are fixed and listed in PLANNING.md.

The robot now uses a hexagon leg layout (corner legs 60 deg round from
the mid legs; the corner coxa brackets need turning on their splines).
Physical limits from a collision sweep of the model are in Config.h:
per-leg coxa limits and LEG_CLEARANCE_MM 56 (a leg is 55.2 mm wide at
the joints); the sim API exports them (version 7). sim_smoke passes.

Unity loads the model (export_unity.py -> Resources/OpenScadModel,
OpenScadModel.cs builds a new rig in place of the old scene's robot).
The PCB model's mounting holes now use the exact EasyEDA grid. README
shows renders of both.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-current/hardware/openscad/export_unity.py

@@ -0,0 +1,109 @@
+"""Export the OpenSCAD robot as meshes for the Unity simulation.
+
+    python export_unity.py            (from hardware/openscad, needs OpenSCAD)
+
+Writes Hexapod_Simulation_Unity/Assets/HexapodSim/Resources/OpenScadModel/*.bytes,
+loaded by Assets/HexapodSim/OpenScadModel.cs. Every file is one rig segment
+in the robot frame (mm, +X forward, +Y left, +Z up), relative to the
+segment's pivot, in the rest pose that matches the rig's zero rotations
+(coxa 0, femur 0, tibia -90):
+  body           Z = 0 on the joint plane (13.5 mm above the bottom plate)
+  leg_<side>_*   left = as leg 4 (mount +90), right = its mirror (mount -90)
+
+File format (little endian): b"HXM1", int32 groups, then per group
+float32 r, g, b, a, int32 triangles, triangles * 9 float32 (x, y, z).
+Triangles wind counter-clockwise seen from outside (right-handed).
+"""
+import os, re, struct, subprocess, sys, tempfile
+
+HERE = os.path.dirname(os.path.abspath(__file__)).replace("\\", "/")
+OUT = os.path.normpath(os.path.join(HERE, "..", "..", "Hexapod_Simulation_Unity", "Assets",
+                                    "HexapodSim", "Resources", "OpenScadModel"))
+OPENSCAD = os.environ.get("OPENSCAD", r"C:/Program Files/OpenSCAD/openscad.exe")
+HEADER = f"use <{HERE}/body.scad>\nuse <{HERE}/leg.scad>\n"
+JOINT_PLANE_Z = 13.5
+
+
+def hexcol(h, a=1.0):
+    h = h.lstrip("#")
+    return [int(h[i:i + 2], 16) / 255 for i in (0, 2, 4)] + [a]
+
+
+# segment -> list of (colour, OpenSCAD geometry in the segment's frame)
+BODY = [
+    ("#3a3a3a", f"translate([0, 0, -{JOINT_PLANE_Z}]) fusion_to_robot() bottom_half();"),
+    ("#555555", f"translate([0, 0, -{JOINT_PLANE_Z}]) fusion_to_robot() top_half();"),
+    ("#2a2a2a", f"translate([0, 0, -{JOINT_PLANE_Z}]) fusion_to_robot() body_servos_uv();"),
+    ("#2b6b3a", f"translate([0, 0, -{JOINT_PLANE_Z}]) pcb_in_body();"),
+]
+LEFT = "rotate([0, 0, 90]) "   # leg frame -> robot frame for the left legs (mount +90)
+LEG = {
+    "coxa": [
+        ("#d9822b", LEFT + "{ coxa_bracket_upper(); coxa_bracket_lower(); }"),
+        ("#bdbdbd", LEFT + "translate([55, 0, 0]) along_y(28.7) horn_adapter();"),
+        ("#5a3a1e", LEFT + "coxa_cables();"),
+    ],
+    "femur": [
+        ("#4a7fbf", LEFT + "{ link_channel(); link_lid(); }"),
+        ("#2a2a2a", LEFT + "link_servos();"),
+        ("#5a3a1e", LEFT + "femur_cables();"),
+    ],
+    "tibia": [
+        ("#5fa35f", LEFT + "{ tibia_bearing_half(); tibia_horn_half(); }"),
+        ("#bdbdbd", LEFT + "along_y(28.7) horn_adapter();"),
+        ("#1c1c1c", LEFT + "foot_sock();"),
+    ],
+}
+
+
+def render(geometry, tmp):
+    scad = os.path.join(tmp, "part.scad"); stl = os.path.join(tmp, "part.stl")
+    with open(scad, "w") as f:
+        f.write(HEADER + geometry + "\n")
+    r = subprocess.run([OPENSCAD, "-o", stl, scad], capture_output=True, text=True)
+    if r.returncode != 0 or not os.path.exists(stl):
+        sys.exit(f"OpenSCAD failed on: {geometry}\n{r.stderr}")
+    tris = []
+    num = r"([-+0-9.eE]+)"
+    for m in re.finditer(r"outer loop\s+vertex\s+%s\s+%s\s+%s\s+vertex\s+%s\s+%s\s+%s\s+vertex\s+%s\s+%s\s+%s" % ((num,) * 9),
+                         open(stl).read()):
+        tris.append([float(v) for v in m.groups()])
+    os.remove(stl)
+    return tris
+
+
+def mirror_y(tris):
+    # (x, y, z) -> (x, -y, z) and swap two vertices to keep outward winding
+    out = []
+    for t in tris:
+        a, b, c = t[0:3], t[3:6], t[6:9]
+        a, b, c = [a[0], -a[1], a[2]], [b[0], -b[1], b[2]], [c[0], -c[1], c[2]]
+        out.append(a + c + b)
+    return out
+
+
+def write(name, groups):
+    path = os.path.join(OUT, name + ".bytes")
+    with open(path, "wb") as f:
+        f.write(b"HXM1" + struct.pack("<i", len(groups)))
+        for col, tris in groups:
+            f.write(struct.pack("<4f", *col) + struct.pack("<i", len(tris)))
+            for t in tris:
+                f.write(struct.pack("<9f", *t))
+    print(f"  {name}: {sum(len(t) for _, t in groups)} triangles")
+
+
+def main():
+    os.makedirs(OUT, exist_ok=True)
+    with tempfile.TemporaryDirectory() as tmp:
+        print("body")
+        write("body", [(hexcol(c), render(g, tmp)) for c, g in BODY])
+        for seg, parts in LEG.items():
+            print("leg", seg)
+            groups = [(hexcol(c), render(g, tmp)) for c, g in parts]
+            write(f"leg_left_{seg}", groups)
+            write(f"leg_right_{seg}", [(c, mirror_y(t)) for c, t in groups])
+
+
+if __name__ == "__main__":
+    main()