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Bug in box-sphere collider #2206

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yuvaltassa opened this issue Nov 4, 2024 · 0 comments
Open
2 tasks done

Bug in box-sphere collider #2206

yuvaltassa opened this issue Nov 4, 2024 · 0 comments
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bug Something isn't working

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@yuvaltassa
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yuvaltassa commented Nov 4, 2024 •
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Intro

MuJoCo dev. Original bug report in #2199

My setup

n/a

What's happening? What did you expect?

The box-sphere collider returns correct contact positions, but the depth (contact.dist) is wrong after full penetration of the sphere into the box.

Steps for reproduction

Run the code below, get this plot

image

Minimal model for reproduction

See below.

Code required for reproduction

xml = """
<mujoco>
  <worldbody>
    <geom name="plane" pos="0 0 -.005" type="plane" size="0.5 0.5 0.01"/>-->
    <geom name="box"   type="box" pos = "0 0 -0.255" size="0.5 0.5 .25"  />
    <body>
      <freejoint/>
      <geom name="sphere" type="sphere" mass="1" size="0.005"/>
    </body>
  </worldbody>
</mujoco>
"""
model = mujoco.MjModel.from_xml_string(xml)
data = mujoco.MjData(model)

depth = np.linspace(-.01, -1e-6, 200)
contact = [[], []]
for z in depth:
  data.qpos[2] = z
  mujoco.mj_forward(model, data)
  for i in range(2):
    c = data.contact[i]
    condata = np.array((c.pos[2], c.dist))
    contact[i].append(condata)

plt.plot(depth, contact[0], label=['plane contact pos', 'plane contact depth']);
plt.plot(depth, contact[1], '--', label=['box contact pos', 'box contact depth']);
plt.xlabel('Penetration (m)');
plt.legend()

Confirmations
@yuvaltassa yuvaltassa added the bug Something isn't working label Nov 4, 2024
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@yuvaltassa