Direct collocation not correctly converting scene graph configuration values

[marip8]

What happened?

After updating from Drake 1.35.0 to 1.36.0, I encounter a run-time error when using the DirectCollocation optimization that says:

RuntimeError: Exception while evaluating SNOPT costs and constraints: 'GetPropertyOrDefault(): The property ('material', 'hunt_crossley_dissipation') exists, but is of a different type. Requested 'drake::AutoDiffXd', but found 'double''

and

RuntimeError: Exception while evaluating SNOPT costs and constraints: 'GetPropertyOrDefault(): The property ('material', 'point_contact_stiffness') exists, but is of a different type. Requested 'drake::AutoDiffXd', but found 'double''

It appears that this might be caused to the changes in default values in the scene graph configuration added by this PR. If I reset the values to hunt_crossley_dissipation=None and point_contact_stiffness=None (their values in Drake 1.35.0), then my DirectCollocation optimization runs correctly again.

Is the issue that the DirectCollocation class is not properly casting these scene graph configuration values from double to AutoDiffXd, or is there just a fundamental conceptual problem using these two values in the optimization?

Version

1.36.0

What operating system are you using?

Ubuntu 22.04

What installation option are you using?

pip install drake

Relevant log output

No response

[jwnimmer-tri]

I think the problem is MultibodyPlant accessing the values using the wrong type annotation. The properties should be accessed using double (not T) or could be omitted and double would be correctly inferred:

drake/multibody/plant/multibody_plant.cc

Lines 1568 to 1575 in d819ff2

	return std::pair(prop->template GetPropertyOrDefault<T>(
	geometry::internal::kMaterialGroup,
	geometry::internal::kPointStiffness,
	penalty_method_contact_parameters_.geometry_stiffness),
	prop->template GetPropertyOrDefault<T>(
	geometry::internal::kMaterialGroup,
	geometry::internal::kHcDissipation,
	penalty_method_contact_parameters_.dissipation));

I think you found the best workaround for now, by setting hunt_crossley_dissipation=None and point_contact_stiffness=None in the config.

[jwnimmer-tri]

Hmm, I just found #13630 which led me to the docs at https://drake.mit.edu/doxygen_cxx/classdrake_1_1multibody_1_1_multibody_plant.html#accessing_contact_properties, which specifies that the properties are of type T not double. So maybe the code which sets defaults in SceneGraph is actually what's wrong.