Add Feature For Robotics Randomization Reset

[MuGdxy]

Related PR(last): #230
Related PR(new): #232

We are attempting to add a new uipc::Feature to support per-object parameter updates and DOF (simulation state) updates.

Discussion:

• The API Naming
• The Behaviour of the API
• API Generalization and Combination

[MuGdxy]

A possible API usage for the Finite Element Entity Simulation State Update.

# get feature
importer:FiniteElementStateImportFeature = world.features().find(FiniteElementStateImportFeature)

# create a geometry to update the state
state_geo = importer.create_geometry(vertex_offset=0, vertex_count=N)

# say: need to update position
pos = state_geo.vertices().create(builtin.position)
view(pos)[:] = np.array([...])

# say: need to update velocity
velocity = state_geo.vertices().create(builtin.velocity)
view(velocity)[:] = 0 # say, set speed to 0

# apply the update
importer.copy_from(state_geo) # copy the provided information from the state_geo (now, positions and velocities)

A possible API usage for the Affine Body Entity Simulation State Update

# get feature
importer:AffineBodyStateImportFeature = world.features().find(AffineBodyStateImportFeature)

# create a geometry to update the state
state_geo = importer.create_geometry(body_offset=0, body_count=N)

# say: need to update transform
trans = state_geo.instances().create(builtin.transform)
view(trans)[:] = np.array([...])

# say: need to update velocity
velocity = state_geo.instances().create(builtin.velocity)
view(velocity)[:] = 0 # say, set speed to 0

# apply the update
importer.copy_from(state_geo) # copy the provided information from the state_geo (now, transform and velocities)

[DH-Ng]

At first glance, I would say this looks good.

But do you perhaps have a tutorial/example for uipc::Feature API.
First time I am seeing something like world.features().find(...).

[DH-Ng]

A remark/idea:

So, we got the problem of possible penetration and the user has to ensure that the new object state doesn't lead to penetration.
I mean, that goes pretty much for Isaac Sim too.
But in Isaac the simulation would just keep running in case of penetration since they use XPBD (or at least a variant of that) right now.

The UIPC simulation would "crash" in this case, right?
Do you think its possible to check for penetration before updating the state and if there is, just not apply the update and give a warning?
And if its possible to do such an penetration-check, I think it should ideally be optional.
This allows users to decide for themselves and keep performance.

I think this is just a little nice-to-have behavior (but very low priority I would say).
This would, for example, be nice to have for prototyping the sim environment.

[MuGdxy]

The UIPC simulation would "crash" in this case, right?

Do you think its possible to check for penetration before updating the state and if there is, just not apply the update and give a warning?

And if its possible to do such an penetration-check, I think it should ideally be optional.

This allows users to decide for themselves and keep performance.

I think this is just a little nice-to-have behavior (but very low priority I would say).

This would, for example, be nice to have for prototyping the sim environment.

In fact, in the current implementation, uipc will launch a sanity check to find and report penetration when calling world.init(...), but it's not suitable for this "Reset" topic, cuz santy-checking always rebuilds the scene, which may take a lot of time. So we need a new checker.

[MuGdxy]

At first glance, I would say this looks good.↳

Butt do you perhaps have a tutorial/example for uipc::Feature API. First time I am seeing something like world.features().find(...).↳

Yep, the example will be provided and so for the specification in documents.

You may check this example:

https://github.com/spiriMirror/libuipc-samples/blob/main/python/20_contact_system_feature/main.py

to understand uipc::Feature facility.

uipc::Feature is a recommended way to extend the world's ability rather than add a new member function to world(e.g. world.advance())

[MuGdxy]

So I think it's better to separate the functionalities to:

1. StateImporters: FiniteElementStateImportFeature/AffineBodyStateImportFeature
   -> Allow users to update the simulation state.
2. PenetrationChecker: SurfacePenerationCheckFeature
   -> Check if any penetration happens, say: if any vertex in a tetrahedron, or if any edge cuts through a triangle.
3. DistanceChecker: SurfaceDistanceCheckFeature
   -> Check if any thickness violation or 0-distance happens.

The 1 will be implemented first, and 2,3 need further discussion.

For now, I will expose the World-Sanity-Check facility to users as a temporary workaround, which means users can call:

world.sanity_check()

after state update.

[DH-Ng]

Sounds good.

Btw, about the name StateImport/StateImporter:
I thinks something like StateUpdate/StateUpdater or StateWrite/StateWriter might be more fitting.
Import makes me think of importing a package/ a file.

[MuGdxy]

We can use StateAccessor for read and write.

[MuGdxy]

A possible API usage for the Finite Element Entity Simulation State Update.

# get feature
accessor:FiniteElementStateAccessorFeature = world.features().find(FiniteElementStateAccessorFeature)

# create a geometry to update the state
state_geo = accessor.create_geometry(vertex_offset=0, vertex_count=N)

# say: need to update position
pos = state_geo.vertices().create(builtin.position)
view(pos)[:] = np.array([...])

# say: need to update velocity
velocity = state_geo.vertices().create(builtin.velocity)
view(velocity)[:] = 0 # say, set speed to 0

# apply the update
accessor.copy_from(state_geo) # copy the provided information from the state_geo (now, positions and velocities)

A possible API usage for the Affine Body Entity Simulation State Update

# get feature
accessor:AffineBodyStateAccessorFeature = world.features().find(AffineBodyStateAccessorFeature)

# create a geometry to update the state
state_geo = accessor.create_geometry(body_offset=0, body_count=N)

# say: need to update transform
trans = state_geo.instances().create(builtin.transform)
view(trans)[:] = np.array([...])

# say: need to update velocity
velocity = state_geo.instances().create(builtin.velocity)
view(velocity)[:] = 0 # say, set speed to 0

# apply the update
accessor.copy_from(state_geo) # copy the provided information from the state_geo (now, transform and velocities)

[MuGdxy]

Example

https://github.com/spiriMirror/libuipc-samples/tree/main/python/31_state_accessor_feature

Results

state_accessor.mp4