Thread: Vector
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Old 09-04-2006, 06:27 AM   #4
Procrastination Incarnate

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Originally Posted by PipeDream
That very simple integration method will always increase or decrease energy since it can only exactly reproduce lines. If you flip the order of adding velocity/acceleration to position/velocity you'll see it decay instead of grow.
Yes, I noticed that, but I didn't want to overdo things for the purpose of a sample. I just decreased the period from 0.02 to 0.01 and hoped nobody would be bored enough to watch the ball long enough to see it bounce out of the arena.

This is a somewhat less interesting demonstration since it doesn't grow in energy and because of that the skidding karukef mentions occurs more frequently.
That can be fixed by increasing the starting velocity. The skidding occurs when the ball lands on a wall close to the ground and bounces out with a near flat velocity. The chances of that happening reduce consderably with longer bounces.

In general for spells the lack of conservation in the simple integrator is not a problem, but it will become one as you increase the time step. .01 is smaller than what is necessary for visually smooth. With this integrator you can safely increase to a less aggressive .03-.05.
Mostly, I think spells won't even want to conserve the speed, few objects bounce perfectly so I imagine users would want to scale down the speed with every bounce anyway.

But in the end, it's up to the users to decide how to utilize these functions, for simple projectile parabola approximations or more detailed and complex physical models.
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