Optional physics features

[chapulina]

Reopening this BitBucket PR, resolves #58.

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Overview

Reduce MinimumFeatureList so that physics engines are not required to implement all features, and some of them are treated as optional.

Bullet

This enables running Bullet with Ignition. You must use ign-physics' bullet_chapulina branch. ⚠️ As of that branch, Bullet is not fully functional yet though. But it loads 🙂

Implementation

This PR makes the following features optional:

• Features for detachable joints:

  • ignition::physics::AttachFixedJointFeature
  • ignition::physics::DetachJointFeature
  • ignition::physics::SetJointTransformFromParentFeature

• Features for bounding box:

  • ignition::physics::GetModelBoundingBox

• Features for joint velocity commands:

  • ignition::physics::SetJointVelocityCommandFeature

• Features for 3D meshes:

  • ignition::physics::mesh::AttachMeshShapeFeature

• For each group of optional features:

  • Create a feature list, i.e. DetachableJointFeatureList
  • Create entity types which use that list, i.e. JointDetachableJointPtrType
  • Create an entity map that holds the specialized entity type, i.e. entityJointDetachableJointMap
  • Use entityCast to cast from the original entity, created with MinimumFeatureList, to the specialized entity. entityCast will also populate the specialized map the first time it's called and get the entity from that map on subsequent calls. This means that RequestFeature is only called once for each combination of entity + feature list.

Any engine implementing all the minimum features will be loaded. If, at runtime, there's an attempt to use an unsupported feature, a warning is printed. That is:

• If a component::DetachableJoint is created, a warning is printed and the joint isn't attached or detached.
• If a components::AxisAlignedBox is created, a warning is printed and the box is not populated.
• If a components::JointVelocityCmd is created, a warning is printed and the command has no effect.
• If a collision has a mesh geometry, a warning is printed and the geometry isn't created.

I'll remove features not needed by TPE on a subsequent PR, that's currently on the chapulina/tpe branch.

[chapulina]

@osrf-jenkins run tests

[azeey]

@chapulina, should we conclude the test failures from thils thread were flaky tests?

[chapulina]

should we conclude the test failures from thils thread were flaky tests?

No, I think they're introduced by this PR. I'll take a look. Also, I'd like to refactor this a bit to prevent some Each calls for unsupported features. Sorry I only remembered all this after reopening the PR.

[chapulina]

should we conclude the test failures from thils thread were flaky tests?

No, I think they're introduced by this PR.

@azeey , I just realized that the test passed on the latest OSX build. 🤔

I'd like to refactor this a bit to prevent some Each calls for unsupported features.

Done on db37fb6. I had thought of caching an engine pointer for each set of features and then just checking that pointer before some Each calls, but I thought that may be overkill? Went instead with breaking the Each loop. Let me know what you think.