[meshcat] meshes set through SetTriangleMesh and SetTriangleColorMesh are all black

[RussTedrake]

What happened?

mu = 1.0
height = .3
N = 50
t = np.linspace(0, 2*np.pi, N)
vertices = np.vstack((height*mu*np.sin(t), height*mu*np.cos(t), height + 0*t))
vertices = np.append(np.array([[0], [0], [height]]), vertices, axis=1)
vertices = np.append(np.zeros((3,1)), vertices, axis=1)
faces = []
for i in range(N):
    faces.append([0, i+2, i+3])
    faces.append([0, i+3, i+2])
    faces.append([1, i+2, i+3])
    faces.append([1, i+3, i+2])
faces = np.asarray(faces, dtype=int).T
meshcat.SetTriangleMesh("my_cone", vertices, faces, rgba=Rgba(0, 0, 1, 1))

produces a black cone. I was hoping for a blue one.

I was not able to resolve this using SetTriangleColorMesh. These methods are not very welll covered in meshcat_manual_test. And the units of the color matrix in SetTriangleColorMesh are not properly documented. [0,1]? [0, 255]? (Sorry! The fault is mine!)

There is a test that uses the TriangleSurfaceMesh (which calls these methods), and renders the color properly.

Version

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What operating system are you using?

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What installation option are you using?

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Relevant log output

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[RussTedrake]

Update: I resolved the color issue. I had 2 faces listed twice. I'm not sure why that broke everything, but the follow code works:

meshcat.Delete()

mu = 1.0
height = .3
N = 50
t = np.linspace(0, 2*np.pi, N)
vertices = np.vstack((height*mu*np.sin(t), height*mu*np.cos(t), height + 0*t))
vertices = np.append(np.array([[0], [0], [height]]), vertices, axis=1)
vertices = np.append(np.zeros((3,1)), vertices, axis=1)
faces = []
for i in range(N-1):
    faces.append([0, i+2, i+3])
    faces.append([1, i+3, i+2])
faces = np.asarray(faces, dtype=int).T
meshcat.SetTriangleMesh("my_cone", vertices, faces, rgba=Rgba(0, 0, 1, 1))