Graal Forums - Programming Exercise #6: The Ice Script

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Programming Exercise #6: The Ice Script

In lieu of: http://forums.graalonline.com/forums...ad.php?t=82343
As I find this topic very interesting:

Graal ice scripts historically have absolutely arbitrary physics. I think that perhaps we need to really evaluate how we make ice skating scripts.

This is what I propose:
Anyone who wants to participate in this exercise will make an ice skating script based on basic movement (disable it in your script if you choose).

I will later today talk with one of the classic server managers to set up a place to upload all these ice scripts, so that each room has a separate ice script for each entry you guys give here. We shall update this ice script house as entries come in.

You all will be able to go skate in these rooms and look at the scripts.

I think we need to look at this with two concepts (two sets of physics):
Program what you think would happen with ice skates on,
and program what you think would happen with normal shoes on.

And the scantily clad babe drops the flag to start...

Here's my entry...
Basically, there are a few coefficients that you can tweak at the top to change how it acts and probably get a bit closer to "real" than what I did, but the physics are pretty exact.
I did take a whole lot of things out of what real ice skating physics would be because we only have a certain level of control (i.e., we can't change what angles the skates are pointing at or exactly how much power we want per stroke), but I made a few estimations as to how to replicate what a normal person would do.

And the code:

PHP Code:


		
			
//#CLIENTSIDE

function onCreated() {

  disabledefmovement();

  

  this.velocity = {0,0,0}; // inital velocity vector

  

  this.power = 1; // power per stroke (should be less than 1 or you might get weird results)

  this.friction = .95; // friction coefficient

  this.collision = -.5; // collision coefficient



  this.scale = .5; // velocity -> tiles



  this.foot = 1; // current foot



  onTimeout();

}



function onTimeout() {

  if (keydown(0) || keydown(1) || keydown(2) || keydown(3)) { // if a key is pressed

    if (this.cooldown <= 0) { // if the cooldown is finished

    

      // alternate current foot

      this.foot = -this.foot;



      // set the ani, would make more sense if I had one for each foot, but just sticking with defaults

      setani("walk", null);

      

      // set the direction

      player.dir = getdir((keydown(3)-keydown(1)), (keydown(2)-keydown(0)));



      // normalized movement vector based on key input

      temp.movement = vectornormalize({(keydown(3)-keydown(1)), (keydown(2)-keydown(0)), 0});

      

      // rotate movement vector slightly based on which foot the stroke is coming from and how fast the player is traveling

      temp.movement = getvectorfromangles(getanglesfromvector(temp.movement)[0]+this.foot*vectorlen(this.velocity)^2.5/8, 0);

      

      // scale movement vector

      temp.movement = vectorscale(temp.movement, this.power);



      // add the movement vector to the player velocity vector

      this.velocity = vectoradd(this.velocity, temp.movement);

      

      // add a cooldown variable until next stroke based on how fast the player is traveling

      this.cooldown = int(vectorlen(this.velocity)*2);

    } else { 

      setani("idle", null);

    }

  } else {

    setani("idle", null);

  }

  this.cooldown--; // decrease cooldown



  if (vectorlen(this.velocity) < .1) { // just so it doesn't do a bunch of calculations for more or less no reason

    this.velocity = {0,0,0};

  } else {

    this.velocity = vectorscale(this.velocity, this.friction); // apply the friction coefficient



    // collision detection



    temp.t = 7;

    for (temp.i = 1; temp.i <= temp.t; temp.i++) { // partition the checking into temp.t parts

      

      // if the next point is not on a wall

      if (!onwall2(player.x+((this.velocity[0]*this.scale)/temp.t), player.y+((this.velocity[1]*this.scale)/temp.t), 2, 3)) {

        // move onto the next point

        player.x += (this.velocity[0]*this.scale)/temp.t;

        player.y += (this.velocity[1]*this.scale)/temp.t;

      } else {

        // scale the vector with the collision coefficient

        this.velocity = vectorscale(this.velocity, this.collision);

      }

    }

  }

  setTimer(0.05);

}

The coefficients I set should more or less replicate a player with ice skates on.

For a player with ice skates off I would probably use the following constants:

PHP Code:


		
			
  this.power = .1; // power per stroke (should be less than 1 or you might get weird results)

  this.friction = .99; // friction coefficient

  this.collision = -.1; // collision coefficient

Are we limited to local NPC scripts, can we use weapons, a combination of the two?

Quote:

Originally Posted by Bl0nkt (Post 1445879)

Are we limited to local NPC scripts, can we use weapons, a combination of the two?

Why would you need to use anything other than a weapon script?

Quote:

Originally Posted by cbk1994 (Post 1445883)

Why would you need to use anything other than a weapon script?

If it's limited to say, a skate park, I'd just put the script in the level.

Quote:

Originally Posted by cbk1994 (Post 1445883)

Why would you need to use anything other than a weapon script?

A local NPC script to define the icy area including the variables for its slipperiness and the weapon which is always active and acts based upon the variables.

Quote:

Originally Posted by xXziroXx (Post 1445943)

If it's limited to say, a skate park, I'd just put the script in the level.

In a class or something, right?

Quote:

Originally Posted by Bl0nkt (Post 1446009)

A local NPC script to define the icy area including the variables for its slipperiness and the weapon which is always active and acts based upon the variables.

Oh, I see what you mean.

Frankly, I don't think it matters how it's implemented. I think what the programming exercise is focused on is the physics and realism.
For example, my script could be tweaked in under a minute to communicate with a class rather than from predefined constants, but it would really have nothing to do with what this programming exercise was designed for. More or less, I'm just trying to say I was aiming to keep it both simple and concise.

I will start this today, thanks to WhiteDragon.

Any other entries? More to follow.

(I hope everyone had a happy thanksgiving to balance out a terrible one of mine:D)