Relations between x y axis and the velocity in pixels?

[chengenzhao]

Hi:

We tried to compare the two velocities and find the relationship between x, y coordinates and the velocity in pixels
the 1st is simply as

var velocity = 6;
physics.setVelocityX(FXGL.getPhysicsWorld().toPixels(velocity);

the 2nd is

var velocity = 6;
entity.setX(entity.getX + velocity);

in theory they should be equal right?
but seems like they are slight different
the 2nd has larger velocity
so if we set 2nd velocity to 5
then seems both are equal
not very sure it is because of this line of source code

jboxWorld.setParticleDensity(1.2f);

so any idea why this happened?
And how to fix this descrepency?

Thanks

[AlmasB]

There are two methods in PhysicsComponent that take velocity: one is in pixels, the other in meters. Velocity is measured by units per second, rather than units per frame (at least as far as I can remember), so something like x += velocity * tpf is a closer comparison.

[chengenzhao]

Got it

physics.setVelocityX(500);

==

entity.setX(entity.getX() + 500*tpf);