URDF documentation Update #222
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sarah-gibson
suggested changes
May 13, 2021
| <collision> | ||
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| The size of the primitive will be set in Unity by changing the scale of gameObject containing UrdfCollision script. |
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This is passive voice, which is a bit confusing. Who will do the setting? Is it the URDF Importer? If so, here's a suggestion: "The URDF Importer will set the size of the primitive using the "scale" parameter of the GameObject that contains the UrdfCollsion script." [if the meaning is still correct]
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| This is done, as opposed to using the size API of the primitive collider, to have consistency across different mesh types. The sizing API is only available for primitive mesh colliders and not for complex collider meshes and visual meshes. Thats why we use the parent's scaling to change the shape of the primitive mesh. This scale is exported as the primitive size during URDF export. |
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Suggestion to improve clarity:
"The reason we set the size via the "scale" of the parent GameObject as opposed to the "size" of the primitive collider is to have consistency across different mesh types; the size API is only available for primitive mesh colliders and not for complex collider meshes and visual meshes, whose size must be changed using their parent GameObject's "scale" parameter."
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I don't understand what the last sentence means - can you clarify?
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Updated the language
vidurvij-Unity
changed the title
sarah-gibson
approved these changes
Jun 7, 2021
hyounesy
reviewed
Jun 30, 2021
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| The reason we set the size via the "scale" of the parent GameObject as opposed to the "size" of the primitive collider is to have consistency across different mesh types; the size API is only available for primitive mesh colliders and not for complex collider meshes and visual meshes, whose size must be changed using their parent GameObject's "scale" parameter. The "scale" parameter of the gameObject is also used set the values of primitive "size" in the URDF when performing an URDF export. |
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- ... is also used [to] set the values of [the] primitive['s] ...
- ... performing [a] URDF export.
hyounesy
suggested changes
Jun 30, 2021
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| <collision> | ||
| <geometry> | ||
| <cylinder size=".4 .3 .4" /> | ||
| </geometry> | ||
| </collision> | ||
| <collision> |
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remove the extra tag at the bottom and reformat:
<collision>
<geometry>
<cylinder size=".4 .3 .4" />
</geometry>
</collision>|
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| ## Disable Collision Support | ||
| URDF defines the robot visually using Visual Meshes, and its collision using Collision Meshes. Collision meshes define the physical volume of the links, and are used to calculate the inertia of the links and also to detect collisions between different physical objects. In Unity, rigidbodies cannot have concave collision meshes, so when importing a concave collision mesh, all concave regions are closed over to produce a convex outline. As a result, the convex shapes might intersect with each other, creating a hindrance in robot movement. To remedy this, we support a ```disable collision``` tag in URDF. To add an exception for collision detection in Unity: | ||
| URDF defines the robot visually using Visual Meshes, and its collision using Collision Meshes. Collision meshes define the physical volume of the links, and are used to calculate the inertia of the links and also to detect collisions between different physical objects. In Unity, RigidBodies cannot have concave collision meshes, so when importing a concave collision mesh, all concave regions are closed over to produce a convex outline. As a result, the convex shapes might intersect with each other, creating a hindrance in robot movement. To remedy this, we support a ```disable collision``` tag in URDF. To add an exception for collision detection in Unity: |
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nit: Rigidbody
Perhaps you can also link it to the documentation. e.g.:
In Unity, Rigidbody components cannot ...
hyounesy
approved these changes
Jul 6, 2021
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| ## Disable Collision Support | ||
| URDF defines the robot visually using Visual Meshes, and its collision using Collision Meshes. Collision meshes define the physical volume of the links, and are used to calculate the inertia of the links and also to detect collisions between different physical objects. In Unity, rigidbodies cannot have concave collision meshes, so when importing a concave collision mesh, all concave regions are closed over to produce a convex outline. As a result, the convex shapes might intersect with each other, creating a hindrance in robot movement. To remedy this, we support a ```disable collision``` tag in URDF. To add an exception for collision detection in Unity: | ||
| URDF defines the robot visually using Visual Meshes, and its collision using Collision Meshes. Collision meshes define the physical volume of the links, and are used to calculate the inertia of the links and also to detect collisions between different physical objects. In Unity, [RigidBodies](https://docs.unity3d.com/ScriptReference/Rigidbody.html) cannot have concave collision meshes, so when importing a concave collision mesh, all concave regions are closed over to produce a convex outline. As a result, the convex shapes might intersect with each other, creating a hindrance in robot movement. To remedy this, we support a ```disable collision``` tag in URDF. To add an exception for collision detection in Unity: |
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consistency nit: RigidB[b]odies, or better [Rigidbody components]
peifeng-unity
pushed a commit
that referenced
this pull request
Jul 16, 2021
* Adding primitive sizing documentation * Add list of supported URDF tags
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Proposed change(s)
Documentation update on primitive sizing
The original issue described the inability of the user to export the size of the primitive he created to the URDF file. He was trying to export the size of the box he created to a URDF file using the export feature but the URDF file always exported the size [1 1 1]. This is an expected behavior because URDF importer does not read or write size of the primitives in the BoxCollider, CapsuleCollider or the Spherical Collider. Instead it change the size of the visual and collider meshes using the scale of the parent gameObject of the mesh.
This is done because:
Adding a list of supported URDF tags
Adding a list of supported URDF tags which are read from a file and attributed to an Articulation Body property in Unity.
Useful links (GitHub issues, JIRA tickets, forum threads, etc.)
https://jira.unity3d.com/browse/AIRO-623
https://jira.unity3d.com/browse/AIRO-642
Unity-Technologies/URDF-Importer#79
Types of change(s)
Testing and Verification
Test the bug by importing and exporting R2D2 URDF file which is made up box primitives.
Test Configuration:
Checklist
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