pybullet.error: getMeshData failed again

[shiyani21]

I am trying to use the getMeshData function for a single cube and I keeping getting error that it has failed. here is the snippet

import pybullet as p import time import pybullet_data

physicsClient = p.connect(p.DIRECT)#or p.DIRECT for non-graphical version p.setAdditionalSearchPath(pybullet_data.getDataPath()) #optionally p.setGravity(0,0,-10) planeId = p.loadURDF("path to plan.urdf") cubeStartPos = [0,0,1] cubeStartOrientation = p.getQuaternionFromEuler([0,0,0]) cube = p.loadURDF("path to cube_10_6_6.urdf",cubeStartPos, cubeStartOrientation) print(p.getMeshData(cube, linkIndex = -1)

i changed the linkIndex to -1 for the base but it still fails cube_10_6_6.zip

[cadop]

Well, maybe not your problem, but your zip file is only a urdf file, there is no mesh in it.

[shiyani21]

I wasn't aware you have a separate mesh file. I used blender to create the cube.

[cadop]

If you look at the urdf file you gave in the zip, Line 17 is <mesh filename="cube_10_6_6.obj" scale=".1 .1 .1"/>. So I think if there is no .obj file, there is no mesh, so possibly thats why you get the error.

[shiyani21]

I did provide a obj file in the zip folder, if not here cube_obj.zip

[shiyani21]

I have all my mtl and obj and urdf file in the same location.

[cadop]

sorry I don't get an error, but it is an empty tuple.

From the documentation it says it is experimental and undocumented, so at least the documentation is accurate in that sense.

I noticed that it does work on softbodies, so maybe it was a feature to help with that.

import pybullet as p
import time
import pybullet_data

physicsClient = p.connect(p.GUI)
p.setGravity(0,0,-10)
cubeStartPos = [0,0,1]
cubeStartOrientation = p.getQuaternionFromEuler([0,0,0])
cube = p.loadURDF("cube_10_6_6.urdf",cubeStartPos, cubeStartOrientation, )
mesh_info = p.getMeshData(cube)
print(mesh_info)

cube_soft = p.loadSoftBody("cube_10_6_6.obj")
meshData = p.getMeshData(cube_soft)
print(meshData)

Running the above code for me yields:

?
(0, ())
(36, ((-0.6279969811439514, -0.6034669876098633, -0.5967980027198792), (-0.6237949728965759, 0.5964879989624023, -0.6062560081481934), (0.09619399905204773, 0.5939909815788269, -0.6031540036201477), (-0.6279969811439514, -0.6034669876098633, -0.5967980027198792), (0.09619399905204773, 0.5939909815788269, -0.6031540036201477), (0.09199199825525284, -0.6059640049934387, -0.5936959981918335), (-0.6331340074539185, -0.5939909815788269, 0.6031540036201477), (-0.628931999206543, 0.6059640049934387, 0.5936959981918335), (-0.6237949728965759, 0.5964879989624023, -0.6062560081481934), (-0.6331340074539185, -0.5939909815788269, 0.6031540036201477), (-0.6237949728965759, 0.5964879989624023, -0.6062560081481934), (-0.6279969811439514, -0.6034669876098633, -0.5967980027198792), (0.08685500174760818, -0.5964879989624023, 0.6062560081481934), (0.09105700254440308, 0.6034669876098633, 0.5967980027198792), (-0.628931999206543, 0.6059640049934387, 0.5936959981918335), (0.08685500174760818, -0.5964879989624023, 0.6062560081481934), (-0.628931999206543, 0.6059640049934387, 0.5936959981918335), (-0.6331340074539185, -0.5939909815788269, 0.6031540036201477), (0.09199199825525284, -0.6059640049934387, -0.5936959981918335), (0.09619399905204773, 0.5939909815788269, -0.6031540036201477), (0.09105700254440308, 0.6034669876098633, 0.5967980027198792), (0.09199199825525284, -0.6059640049934387, -0.5936959981918335), (0.09105700254440308, 0.6034669876098633, 0.5967980027198792), (0.08685500174760818, -0.5964879989624023, 0.6062560081481934), (0.09619399905204773, 0.5939909815788269, -0.6031540036201477), (-0.6237949728965759, 0.5964879989624023, -0.6062560081481934), (-0.628931999206543, 0.6059640049934387, 0.5936959981918335), (0.09619399905204773, 0.5939909815788269, -0.6031540036201477), (-0.628931999206543, 0.6059640049934387, 0.5936959981918335), (0.09105700254440308, 0.6034669876098633, 0.5967980027198792), (-0.6279969811439514, -0.6034669876098633, -0.5967980027198792), (0.09199199825525284, -0.6059640049934387, -0.5936959981918335), (0.08685500174760818, 
-0.5964879989624023, 0.6062560081481934), (-0.6279969811439514, -0.6034669876098633, -0.5967980027198792), (0.08685500174760818, -0.5964879989624023, 0.6062560081481934), (-0.6331340074539185, -0.5939909815788269, 0.6031540036201477)))

I'll comment again if I find anything more in the future.

[shiyani21]

Thank you, I am also working on it but haven't really had any luck until your post. so, thank you tons

[erwincoumans]

The feature is very limited. In a nutshell, your collision shape needs to be a mesh (obj file), not an implicit shape (cube, sphere etc). Then you need to iterate over all collision shapes. Attached is an example. getmesh.zip

So generally it is best to just write your own mesh/obj parser or use assimp.

[cadop]

I was confused at first running the sample code without the updated urdf.

For future people:

The original urdf file was:

    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
                <mesh filename="cube_10_6_6.obj" scale=".1 .1 .1"/>
      </geometry>
       <material name="white">
        <color rgba="1 1 1 1"/>
      </material>
    </visual>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <box size="1 1 1"/>
      </geometry>
    </collision>

Which in the collision tag had geometry as a box.

Instead it should be:

    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
                <mesh filename="cube_10_6_6.obj" scale=".1 .1 .1"/>
      </geometry>
       <material name="white">
        <color rgba="1 1 1 1"/>
      </material>
    </visual>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
            <mesh filename="cube_10_6_6.obj" scale=".1 .1 .1"/>
      </geometry>
    </collision>

So it seems to use the collision shape info, not visual shape.