btConeShapeZ and collision margin

[marcimatz]

Hello,

I am not sure if this is intended or something that was overlooked but I noticed following about collision margins (version 2.76 R1971:

btBoxShape-btBoxShape: 0 cm
btCylinderShapeZ-btBoxShape: 0 cm
btSphereShape-btBoxShape: 0 cm
btConeShapeZ-btBoxShape: 4 cm
btCylinderShapeZ-btCylinderShapeZ: 0 cm
btSphereShape-btCylinderShapeZ: 0 cm
btConeShapeZ-btCylinderShapeZ: 4 cm
btSphereShape-btSphereShape: 0 cm
btSphereShape-btConeShapeZ: 4 cm
btConeShapeZ-btConeShapeZ: 8 cm

It seems to me that the btConeShapeZ might have a problem (or different default setting) compared to the other collision shapes. Trying to set the btConeShapeZ collision margin to 0 with setMargin(0.0f) doesn't do anything. It also seems to have no effect with the other collision shapes mentioned above.
Did I misunderstand something?

[marcimatz]

Well, I just noticed why the setMargin didn't have an effect: I wrap all collision shapes in a compound shape in order to freely adjust the inertia position/orientation relative to the shape, and I was setting the margin of the compound shape.

Setting the margin of the btConeShapeZ to zero works fine (it removed the gap of 4 or 8 centimeters, see above), but my question remains: why this difference with the btConeShapeZ (compared with btBoxShape, btCylinderShapeZ or btSphereShape where the margin doesn't need any adjustment)?

Thanks