Time-based movement: recommended?

[Tenry]

Is it a good idea to do time-based movement instead of frame-based? I see, the pro is that the speed seems constant on every computer even though it's old. But what about the negatives? What, if object A misses collision with object B because it goes completely through it by 1 frame?

const float Speed = 50.f;
float Left = 0.f;
float Top  = 0.f;

while (App.IsOpened())
{
    if (App.GetInput().IsKeyDown(sf::Key::Left))  Left -= Speed * App.GetFrameTime();
    if (App.GetInput().IsKeyDown(sf::Key::Right)) Left += Speed * App.GetFrameTime();
    if (App.GetInput().IsKeyDown(sf::Key::Up))    Top  -= Speed * App.GetFrameTime();
    if (App.GetInput().IsKeyDown(sf::Key::Down))  Top  += Speed * App.GetFrameTime();
}

[Laurent]

If your app is able to produce this kind of situation, then you should check collisions with the line from the previous position to the next one, instead of the just the next position point. This way you can never go through a wall.

But collision detection and physics computing are generally more reliable with a fixed timestep anyway.

[MorleyDev]

A very good article on timesteps and fixing them can be found here:
http://gafferongames.com/game-physics/fix-your-timestep/

[Tenry]

If your app is able to produce this kind of situation, then you should check collisions with the line from the previous position to the next one, instead of the just the next position point. This way you can never go through a wall.

But collision detection and physics computing are generally more reliable with a fixed timestep anyway.

Exactly what I thought, too.

A very good article on timesteps and fixing them can be found here:
http://gafferongames.com/game-physics/fix-your-timestep/

Okay, I will take a look at that, maybe it helps