Restitution doesn't seem right sometimes

In the following gif both cats share the same physics properties.

Cats’ restitution is set as 0.1 Ground restitution is set as 0.8

Everything was created using the Matter.Bodies.rectangle.create(x,y,w,h,o) constructor.

The cats bounce normally unless their rotation is set to an angle between 71 and 109 degrees (~1.22 to ~1.91 radians). As soon as the rotation goes to 70 or 110 degrees the cats bounce normally.

Here’s a fiddle for reproducing this.

Is that expected behavior?

I’ve also noticed that static bodies’ restitution doesn’t play a role in physics simulation. Is that correct?

[TiagoMarinho]

Setting inertia to infinity solves my problem entirely, but while your explanation on why this could be expected behavior seems right to me, I don’t get why this problem only happens for my simulation when the left rectangle is set to an angle EXACTLY between -71 and -109, and as soon as it go to -70 or -110 (same applies for positive rotations) the restitution fixes itself. Here’s a demo:

-80° (it looks like this since -109°):

-71°:

-70°:

Seen from this perspective this looks like unexpected behavior, doesn’t it? Anyway, not a big issue after all, just a little weird collision response. Feel free to close the issue if you think this is not a bug at all.

Also, I’m okay with the static bodies’ predefined restitution.

[rsmmnt]

little update - i figured it out, if you create a body like this: var rect = Matter.Bodies.rectangle(x, y, width, height, { isStatic: true, restitution: 0.9 }

restitution is set to 0 anyway, you should modify restitution manually after body creation