How to prevent character from rotating when moving at an angle to an incline

Question

You can see the problem when moving at an angle to the collider: https://8observer8.github.io/webgl10-js/lighthouse-oimophysics-webgl-js/

I use OimoPhysics but there is no such tag. This is a task common to all physics engines. There is a ball that slides down an inclined surface. It will rotate around an axis pointing upwards in the direction of greatest friction. It can only rotate around the upward axis, rotations around the other axes are frozen.

I created the issue on OimoPhysics GitHub page: https://github.com/saharan/OimoPhysics/issues/65

Another issue on Cannon ES GitHub page with source code in Three.js: https://github.com/pmndrs/cannon-es/issues/183

• PlayCode: https://playcode.io/1507281

But Ammo.js doesn't have this problem. I just replaced OimoPhysics with Ammo.js and the problem went away: https://8observer8.github.io/webgl10-js/lighthouse-ammo-webgl-js/

Ammo.js works for bigger angle (42 degrees) too:

Answer 1

I solved this problem. You need to set the rotation factor to (0, 0, 0) when W and S were pressed, and to (0, 1, 0) when A and D were pressed.

Example on OimoPhysics and Three.js: https://playcode.io/1508199

            if (input === "u") {
                /* ... */
                playerBody.setRotationFactor(new OIMO.Vec3(0, 0, 0));
            }

            if (input === "d") {
                /* ... */
                playerBody.setRotationFactor(new OIMO.Vec3(0, 0, 0));
            }

            if (input === "l") {
                /* ... */
                playerBody.setRotationFactor(new OIMO.Vec3(0, 1, 0));
            }

            if (input === "r") {
                /* ... */
                playerBody.setRotationFactor(new OIMO.Vec3(0, 1, 0));
            }