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  multiply a variable with a delta timestep  (Read 1581 times)
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Offline orange451

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Projects: 8
Exp: 8 years


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« Posted 2015-07-28 03:44:50 »

In a small test project I recently started, I tried an differential approach to friction instead of a linear approach to friction.

For example, before I would do:
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Vector normal = velocity.getNormal();
float magnitude = velocity.getMagnitude();
float change = magnitude - (friction * delta);
velocity = normal.multiply(change);

//

x += velocity.x * delta;
y += velocity.y * delta;


In my current project I am doing:
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velocity = velocity.multiply(0.99);

//

x += velocity.x * delta;
y += velocity.y * delta;


This new method feels much nicer as friction, but it has one draw-back, I cannot use it with a delta timestep! How should I approach this?

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Offline cylab

JGO Kernel


Medals: 195



« Reply #1 - Posted 2015-07-28 08:30:22 »

If you have any kind of physics simulation, I strongly suggest to switch to fixed timestep instead of variable timestep with delta time. Just make with a decent gameloop, that you get a constant fixed update rate for your simulation. This will make it much easier and you also get deterministic reproducible behaviour.

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Offline Riven
Administrator

« JGO Overlord »


Medals: 1371
Projects: 4
Exp: 16 years


Hand over your head.


« Reply #2 - Posted 2015-07-28 11:32:06 »

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- velocity = velocity.multiply(0.99);
+ velocity = velocity.multiply(1.00 - 0.01 * delta);

//

x += velocity.x * delta;
y += velocity.y * delta;



Having said that - use fixed timestep instead.

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