Hi Gamdev-Community,

this is my first post on this board, so i'm gonna introduce myself shortly:

My name is Daniel and I'm a Computerscience-Student from Germany.

I stumbled upon a problem I couldn't find a solution for.

I'm using the SDL2-Library and I try to accomplish a game loop that updates 25 times a second and renders as fast as the machine allows it to.

I want the movements for my game objects as smooth as possible but I don't know how.

I made a graphic to show my problem.

[attachment=26011:smooth_render.jpg]

The upper graph shows the type of rendering I'm trying to achieve.

The lower graph shows the actual result I get.

The idea is, when I set for example the speed of a game object to 5, it shouldn't jump from 0 to 5, but from {(0,1), (1, 2), ..., (4, 5)}.

25 times a second the object gets updated so every 25th of a second the object moves from its current position to (current position) + 5.

But between every update it gets rendered as ofthen as the computer allows it to. And in this (rendering)time, it should move smoothly to the new position.

There must be an interpolation or something to achieve this. The problem is that SDL only allows natural numbers (integer) for its x and y values on the screen.

(No OpenGL suggestions please!)

I hope I made my point clear.

Greetings,

Daniel

Just remember the next older position and interpolate between it and the new position, using the fraction of time passed inbetween as interpolation factor.

If you insist on using that integer only API, you can just round your floats to the nearest int when calling it.

You also should read http://gafferongames.com/game-physics/fix-your-timestep/ .

Okay thank you guys! I will try your approaches und post my progress.

@CC Ricers:

SDL2 is hardware accelerated ;-) You can choose between software and hardware acceleration in your renderer.

I got it working!

Thanks a lot to all of you.

My objects render method looks something like this:

void Player::draw(float interpolation) {
  
  m_renderPosition.x = (m_currPosition.x - m_oldPosition.x) * interpolation + m_oldPosition.x;
  m_renderPosition.y = (m_currPosition.y - m_oldPosition.y) * interpolation + m_oldPosition.y;

  p_texture->draw(m_renderPosition.x, m_renderPosition.y, m_width, m_height);
}

The game loop and interpolation calculation I used is from deWiTTERS.