# How to make spheres bounce travel horizontally and bounce endlessly

Made a new project, starter content, made a new blueprint, gave it the material sphere staticmesh, it has collision built in it. set it to simulate physics, disable gravity, constrain it to a plane, on beginplay i give it linear velocity in the x direction of 200. when i play it, it moves correctly, but i cant make it bounce of the wall and travel back.

ive tried a physical material with a friction of 1, restitution 1000 and density 1.

… what do i need to do to make it bounce off the wall and travel to the opposing wall and then bounce off it?

I’m facing the same problem but my solution isn’t a proper answer in regards to using UE4’s actual physics engine. My solution at the moment is to not use UE4’s physics at all and instead to write a very simple physics engine which is easy enough and only use UE4’s collision detection system.

Sometimes a simpler physics system is a better solution but I would still like to see how this may be done with UE4’s built in physics engine.

If you’d like to know more about writing a simply physics engine, check out the free online book Nature of Code by Daniel Shiffman. He also has a video series based on the book host at Vimeo.

Does the ball stop when it hits the wall?

Ball hits wall and stops, later I cranked up the speed and it worked and bounced correctly, but it slowed down per impact, linear damping was 0 friction 0 restition was 1. And once it got to a low enough speed the ball just snapped to the wall and stops.

Later still I realized restitution 2 made it increase in speed per bounce, and 1.712 made it barely slow down over time.

Found a new bug too, if u have two spheres moving about bouncing off of each other and they’re velocity are kinda parallel only the back one will bounce.

Said another way, if ball A is traveling 100 in the x, and ball B is traveling 200 in the x and collides with the back of ball A, ball B will bounce off of A but A won’t react at all. (Assuming both have the same mass b would travel at 100 and a at 200 after collision). This bug is apparent even at 90 degree collision on the back end of either sphere.

Thanks for the info, I’ll check it out.

I’m really only wanting 2d collisions of 3d objects constrained to a plane, I wasn’t thinking it would be this intense.

Did you change physical mats of both wall and ball? I made it bounce endlessly this way with just physics.