Real time applications, such as games, have a variable FPS. They sometimes run at 60FPS, or when suffering slowdowns, they will run on 40FPS or less.

If you want to change a VALUE from A to B in 1.0 seconds you can't simply increase A by B-A between two frames because frames can run fast or slow, so one frame can have different durations.

The WAY to correct this is to measure the time taken from frame X to X+1 and increment A, leveraging this change with the frame DURATION deltaTime by doing A += (B-A) * DeltaTime.

When the ACCUMULATED DeltaTime reaches 1.0 second, A will have ASSUMED B value.

Real time applications, such as games, have a variable FPS. They sometimes run at 60FPS, or when suffering slowdowns, they will run on 40FPS or less.

If you want to change a value from A to B in 1.0 seconds you can't simply increase A by B-A between two frames because frames can run fast or slow, so one frame can have different durations.

The way to correct this is to measure the time taken from frame X to X+1 and increment A, leveraging this change with the frame duration deltaTime by doing A += (B-A) * DeltaTime.

When the accumulated DeltaTime reaches 1.0 second, A will have assumed B value.