RE: How do you write tests if you aren't sure what the result should be?

Oh, I completely missed that... Frame rate has a specific meaning vis-à-vis
the number of screen refreshes.

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Avi Kessner
Sent: Monday, February 18, 2013 12:53 PM
To: [email protected]
Subject: Re: [TDD] How do you write tests if you aren't sure what the result
should be?

Once we have separated the rendering from the time keeper, you are correct.
However, previously we(I?) was using "frame rate" as a simple term to refer
to how often the function gets called.  (Before it was recognized that
rendering and timers can be separated)

brought to you by the letters A, V, and I and the number 47


On Mon, Feb 18, 2013 at 10:26 PM, Amir Kolsky <[email protected]> wrote:

> **
>
>
> One more question regarding the actual calculation.
>
> The question that comes to mind is "what is the trigger that causes 
> the penguin to be rendered on the screen?" Is there some internal timer?
> External timer?
> In either case, if we separate the drawing trigger from the actual 
> drawing, then the calculation becomes.
>
> Dt = prevTime - now()
> And
> X = prevX + incrementX(dt) (based on whichever factors you want to 
> take into account when moving, deceleration, friction, etc.).
>
> The frame rate does not play into this calculation at all.
>
> What am I missing?
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Esko 
> Luontola
> Sent: Monday, February 18, 2013 12:10 PM
> To: [email protected]
> Subject: Re: [TDD] How do you write tests if you aren't sure what the 
> result should be?
>
> Ron Jeffries wrote on 17.2.2013 13:39:
> > OK, well, he's moving 15 per tick. But now on the new iPad I get 60 
> > ticks
> and he should move about half that.
> > I should generalize this.
> > Hm, well, I want him to go 900 pixels in 2 seconds. That's 450 
> > pixels per
> second.
> > Um, maybe if I just read out the actual time since last time I can 
> > use
> that.
> > So I'll save time in timeThen and read time now and difference them.
>
> If we happen to have some domain knowledge of game development and 
> common patterns in game design, we might decide to decouple the 
> physics time step from the frame rate [1] and use a fixed time step 
> for the physics, to keep the physics calculations deterministic. For 
> example the game Supreme Commander (2007) does its physics calculations at
10 fps, as said in [2]:
>
> "Take a look at the video if you haven't already. What frame rate do 
> you think the game is running at? The correct answer is 10 frames per
second.
> Wait, what? It looks far smoother than 10 fps you say! It is and it isn't.
> The game is actually running at two separate frame rates."
>
> To make the visuals update at a smoother pace, the game state is 
> interpolated to match the frame rate. There are various techniques for 
> interpolating/dead reckoning [3][4], but that's a whole nother story.
>
> [1] http://gafferongames.com/game-physics/fix-your-timestep/
> [2]
>
> http://www.altdevblogaday.com/2011/07/09/synchronous-rts-engines-and-a
> -tale-
> of-desyncs/
> [3]
>
> http://www.gamasutra.com/view/feature/3230/dead_reckoning_latency_hidi
> ng_for
> _.php
> [4]
>
> http://www.gamedev.net/page/resources/_/technical/multiplayer-and-netw
> ork-pr
> ogramming/targeting-a-variation-of-dead-reckoning-r1370
>
> --
> Esko Luontola
> www.orfjackal.net
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>  
>


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