I want to roll ball soft balls down a slide or chute but the soft body balls are passing through the surface.

Here are screenshots at a point in the animation showing the soft body objects passing through the surface

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What could be causing the collision not to work as would be expected?

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    $\begingroup$ I think you need to add more detail. Remember that anyone trying to help you needs to know exactly what you’re experiencing and what you’re trying to achieve. Please describe what each screenshot shows and in what way it isn’t doing what you require - and exactly what you’re trying to achieve. My best guess from those images is that you’re trying to roll apples out of a cart...? $\endgroup$ – Rich Sedman Feb 12 '18 at 15:54
  • $\begingroup$ Yes I want to roll ball soft balls through slider $\endgroup$ – Prashant Vyas Feb 12 '18 at 15:58
  • $\begingroup$ So the balls are Soft Body. Check the direction of the normals of the chute (cube.001). If those are pointing inwards (which they will be if you started with a cube and just removed some faces) then that could be the start of your problems as the soft bodys will behave as if they are inside a surface rather than bouncing off it. $\endgroup$ – Rich Sedman Feb 12 '18 at 16:18

For soft body collision to work correctly the normals of the collision mesh need to be oriented in the right direction - ie, in the direction of the collision. For example, in the case of a simple chute created from a cube by removing some faces you would need to Flip Normals to ensure that they are pointing 'inwards' as shown :

correct normals

Note how the normals (the light-blue lines) are pointing 'inwards'. To 'flip' the normals you can simply go into Edit mode (Tab), select all (A until all mesh is selected), press Space and type 'Flip Normals' and Enter. To display the normals, press N and scroll down to 'Display' and activate display of the normals (when in Edit mode).

This can produce the following result :


Note : It's usually good practice to have 'solid' (manifold) meshes - rather than having single faces with no width (eg, a cube with some faces removed). For a manifold mesh the normals would all point 'out' of the surface, meaning this problem would not occur as collisions would only occur from the 'outside'.

Blend file included

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