Help getting a ball to roll straight

Soon after I got blender I was more planning on making games with it then making 3D images, but now i’m taking a second look at the engine and one of the games I started with it. You control a ball, and yes I can get it to move correctly when rigid body physics isn’t on but you turn it on and it doesn’t roll correctly. For example, I press the up arrow and instead of moving away from the camera at it’s start position it tries to roll sideways instead, basically how can I get so it rolls ONLY in the direction I tell it to go without going sideways.

Woohoo, I get to answer the easy question. Since you already understand all the basic stuff this shouldn’t be too hard to point out for you.

Since rigid body is turned on the balls axis is constantly changing. Ok you have a ball. You’re looking in top view mode (7). The axis of the ball is y pointing to top of screen, x pointing to right of screen, and z pointing into the screen. Ok, rigid bodies is turned on and you want to make it roll in the y direction.

You probably give it a force of say 10 in the y direction. However, you find out that it doesn’t roll correctly and it gets all messed up. On default the “L” all the way to the right of the Force in the Motion actuator is depressed (darkened). Click on it and it should be unpressed (lightened). Now try it again and it should work.

This is because when “L” is depressed force is given to local Y axis (which changes because rigid bodies is on. When it’s unpressed force is given to the global Y which is just force given in the Y direction so it doesn’t matter if the Y axis of the ball is changing.

Long explaination, but I hope you understand.

Jason Lin

Ah thanks, I didn’t know that little “L” button was the culprit (in fact I wasn’t sure what it was but now I kind-of understand it) :slight_smile: