# How to compute time to move

Hello there,

i have a problem with moving textures in OpenGL (using LWJGL).
In my app the character moves on the ground to the next tile.

the distance for X is computed like this:

``````
float movex = 100f * time; //where time is the time per frame
``````

When i move like this, the whole tile map start to flicker (in particular textures with a black border).

This happens because the time is not constant every frame (time = 0.01 frame 1, time = 0.0003f frame 2, …)

If i move like this:

``````
float movex = 100f; //no time is taken
``````

the world and the char move smoothly to the next tile.

My question is:
How do I have to compute the time that:
[ul][]the drawn tiles do not start flicker/shake[]the time to run from tile a to tile b is equal on every pc on this world[/ul]

vsync on

or filter the frame-time (lowpass filter)

or count frames per second, keep the “frametime” constant for the whole second, (calculate it only once every second).

vsync is on…

what would you recommend?

can you point the way to a low pass filter?

i now update the time per frame only every second.

the flickering does not stop

i think it has something to do with the float value i compute as distance.

could it be that the decimal of the float can messup the tile map?
is there any option i can set to tell opengl “not to be so hard” on the float glVertex information?

Flickering ? Should (almost) never happen with both double-buffering and vsync.

What is the granularity of your time measurment ? Most of the milliseconds value are in fact only updated less than hundred times per second. You can very by just doing a tight loop of println(time) to have an idea.

the time is about 0.01615625 every frame…

then i compute:

``````float movex = 100f * time; //where time is about 0.01615625
``````

with this the tile map (grass, fence, trees,…) start to shake/flicker…

I made some tests and found out, when i move (only think in x direction) from 0.0 to 0.50 in x direction then i get this picture:

if i move 0.01 further (= 0.51)
then i get this one:

as you can see, in the second picture there are parts of a black border on the fence.
If i move 0.01px more to the right (0.52) i see it as it is on the first picture! It happens on every .5 px pos…

And this generates a nasty “flickering”!

any suggestions?

Pixel art needs integer pixel precise moves.

Using GL_LINEAR filtering will help a bit smoothing the moving texture.
But the only correct way for pixel art is to always move on integer coordinates.