warp.sim Migration Guide#
This guide is designed for users seeking to migrate their applications from warp.sim to Newton.
Solvers#
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Importers#
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The joint-specific arguments to the importers have been removed.
Instead, you can set the default joint properties on a newton.ModelBuilder instance in the newton.ModelBuilder.default_joint_cfg attribute.
For example, limit_lower is now defined using builder.default_joint_cfg.limit_lower, where builder is an instance of newton.ModelBuilder.
Similarly, the shape contact parameters have been removed from the importers.
Instead, you can set the default contact parameters on a newton.ModelBuilder instance in the newton.ModelBuilder.default_shape_cfg object before loading the asset.
For example, ke is now defined using builder.default_shape_cfg.ke, where builder is an instance of newton.ModelBuilder.
The MJCF and URDF importers both have an up_axis argument that defaults to +Z.
All importers will rotate the asset now to match the builder’s up_axis (instead of overwriting the up_axis in the builder, as was the case previously for the USD importer).
newton.ModelBuilder.add_usd() accepts both file paths and URLs directly, so a separate
resolve_usd_from_url() helper is usually unnecessary when migrating from warp.sim.
The MJCF importer from Warp sim only uses the geom_density defined in the MJCF for sphere and box shapes but ignores these definitions for other shape types (which will receive the default density specified by the density argument to wp.sim.parse_mjcf). The Newton MJCF importer now considers the geom_density for all shape types. This change may yield to different simulation results and may require tuning contact and other simulation parameters to achieve similar results in Newton compared to Warp sim.
Model#
newton.Model.shape_is_solid is now of dtype bool instead of wp.uint8.
The Model.ground attribute and the special ground collision handling have been removed. Instead, you need to manually add a ground plane via newton.ModelBuilder.add_ground_plane().
Newton’s public spatial_vector arrays now use (linear, angular) ordering.
For example, newton.State.body_qd stores (lin_vel, ang_vel), whereas
warp.sim followed Warp’s native (ang_vel, lin_vel) convention. See
Newton Conventions.
The attributes related to joint axes now have the same dimension as the joint DOFs, which is
newton.Model.joint_dof_count. newton.Model.joint_axis remains available and is
indexed per DOF; use newton.Model.joint_qd_start and newton.Model.joint_dof_dim
to locate a joint’s slice in the per-DOF arrays.
For free and D6 joints, Newton stores linear DOFs before angular DOFs in per-axis arrays. In
particular, floating-base slices of newton.State.joint_qd, newton.Control.joint_f,
newton.Control.joint_target_pos, and newton.Control.joint_target_vel use
(lin_vel, ang_vel) ordering, whereas warp.sim used (ang_vel, lin_vel).
warp.sim |
Newton |
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Removed |
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Removed |
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Note: these coefficients are now interpreted as absolute values rather than being scaled by the friction coefficient. |
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Note: these coefficients are now interpreted as absolute values rather than being scaled by the friction coefficient. |
Forward and Inverse Kinematics#
The signatures of the newton.eval_fk() and newton.eval_ik() functions have been slightly modified to make the mask argument optional:
warp.sim |
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Control#
The newton.Control interface is split by responsibility:
newton.Control.joint_target_pos and newton.Control.joint_target_vel store per-DOF
position and velocity targets, newton.Control.joint_act stores feedforward actuator input,
and newton.Control.joint_f stores generalized forces/torques. Unlike warp.sim,
joint_act is no longer the target array.
In order to match the MuJoCo convention, joint_f includes the DOFs of the
free joints as well, so its dimension is newton.Model.joint_dof_count.
JointMode has been replaced by newton.JointTargetMode. Direct force control
corresponds to newton.JointTargetMode.EFFORT together with
newton.Control.joint_f, while simultaneous position and velocity target control uses
newton.JointTargetMode.POSITION_VELOCITY together with
newton.Control.joint_target_pos and newton.Control.joint_target_vel.
ModelBuilder#
The default up axis of the builder is now Z instead of Y.
Analogously, the geometry types plane, capsule, cylinder, and cone now have their up axis set to the Z axis instead of Y by default.
warp.sim |
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It is now possible to set the up axis of the builder using the up_axis attribute,
which can be defined from any value compatible with the AxisType alias.
newton.ModelBuilder.up_vector is now a read-only property computed from newton.ModelBuilder.up_axis.
The ModelBuilder.add_joint_*() functions now use None defaults that are filled in from
the fields of newton.ModelBuilder.default_joint_cfg.
Newton uses world_count throughout the public API (for example in
newton.ModelBuilder.replicate() and newton.Model.world_count); older num_envs
terminology is obsolete.
The ModelBuilder.add_joint*() methods no longer accept linear_compliance and angular_compliance arguments
and the Model no longer stores them as attributes.
Instead, you can pass them as arguments to the newton.solvers.SolverXPBD constructor. Note that now these values
apply to all joints and cannot be set individually per joint anymore. So far we have not found applications that require
per-joint compliance settings and have decided to remove this feature for memory efficiency.
The newton.ModelBuilder.add_joint_free() method now initializes the positional dofs of the free joint with the child body’s transform (body_q).
The universal and compound joints have been removed in favor of the more general D6 joint.
Collisions#
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collide() allocates and returns a contacts buffer when contacts is omitted.
For more control, create a CollisionPipeline directly.
Renderers#
warp.sim |
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