Custom robot (GRiD codegen workflow)#

HJCD-IK’s kinematics are generated from a URDF by GRiD into csrc/generated/grid.cuh.

Regenerate grid.cuh#

python scripts/codegen/generate_grid.py path/to/robot.urdf -t <ee_target_frame>

  • -t selects the fixed end-effector target frame (e.g. panda_grasptarget_hand).

  • Output is the stock generated header — never hand-edit it.

  • Robot constants (NUM_JOINTS, topology counts) are baked per-URDF; the solver reads them from the generated symbols, so don’t hardcode sizes.

Then rebuild: python -m pip install -e ..

Collision (bring-your-own-URDF)#

Add --collision to bake GRiD’s grid_collision spheres (and self-collision ranges) into the same grid.cuh — no hand-written per-robot collision code:

# spherize the URDF's own collision meshes:
python scripts/codegen/generate_grid.py path/to/robot.urdf -t <ee_target> --collision --collision-res 0.05
# or read a pre-spherized foam URDF (when the URDF's meshes don't resolve on disk, e.g. Panda):
python scripts/codegen/generate_grid.py path/to/robot.urdf -t <ee_target> --collision --spherized-urdf path/to/robot_spherized.urdf

Caveats#

  • The solver currently assumes revolute/prismatic/fixed joints, no kinematic loops.

  • Without --collision the build runs open-world; a collision_free=True request is ignored (the collision path is compiled out via the HJCD_HAS_COLLISION sentinel).

  • Keep the EE-target frame consistent with FLANGE_IDX usage in the kernel.