Notch trying jsFiddle • Hacker News Board

Re: Notch trying jsFiddle

#31

Post by dudus » Sun, Dec 02, 2012, 11:19 PM UTC

experiment0 wrote: post #19

antirez wrote: post #16

Earlier quoted context omitted.

No I really mean low level :-) Javascript is high level, but here notch is using it as a low level framebuffer.

> And indeed it is pretty impressive how fast the rendering happens given that the code operates at such lower level. Sorry if this is a stupid question, but wouldn't you normally expect low level code, whilst more time consuming to write, be faster or just as fast as higher level code. For example, how C is used as a standard for fast code since it's so low level.

You would expect low level code to be very fast in a low level language because it runs directly on metal. But on a high level language low level code get's translated into another code, so the code runs on the hardware is much more complicated. By using the high level features on Javascript actually leads to better optimized low level code.

Re: Notch trying jsFiddle

#32

Post by antirez » Sun, Dec 02, 2012, 11:19 PM UTC

experiment0 wrote: post #19

antirez wrote: post #16

Earlier quoted context omitted.

No I really mean low level :-) Javascript is high level, but here notch is using it as a low level framebuffer.

> And indeed it is pretty impressive how fast the rendering happens given that the code operates at such lower level. Sorry if this is a stupid question, but wouldn't you normally expect low level code, whilst more time consuming to write, be faster or just as fast as higher level code. For example, how C is used as a standard for fast code since it's so low level.

If you are using C, you can afford to compute everything at low level as Notch is doing in this example. And you can afford writing pixel by pixel into a frame buffer that is later rendered.

However if you use this approach in Javascript you get poor performances unfortunately. And indeed this demo requires fast computers to do what otherwise could be done in C with direct access to the video frame buffer with maybe 50 times slower computers.

Even C coders almost no longer try to do this low level things and let the graphic chip do a lot of the work when the goal is to produce a game.

So in Javascript instead you want to usually call a library that implements a 3D engine in a lower level language like C and with more direct hardware access.

But in this case, it makes sense to do all this in a low level way and in Javascript: it is just a demo that is full of interesting code and with an appealing visual output.

Re: Notch trying jsFiddle

#33

Post by shocks » Sun, Dec 02, 2012, 11:21 PM UTC

    setInterval(clock, 1000 / 100);

Is there any reason for writing 1000/100 instead of 10?

edit: Thanks guys!

Re: Notch trying jsFiddle

#34

Post by JungleGymSam » Sun, Dec 02, 2012, 11:22 PM UTC

Why is the framerate poor even when I shrink the viewing area down 10x10? It seems to have the same stutter as the original large view. Is it because it's doing the same calculations but just showing fewer pixels?

Re: Notch trying jsFiddle

#35

Post by ewolfe » Sun, Dec 02, 2012, 11:24 PM UTC

tgandrews wrote: post #4

Can anyone explain how this works? I never have got to grips with 3D.

It looks like he's using a matrix to create cartesian coordinates in a model-view space and then performing some basic linear algebra on the points to animate it. For a primer on 3D worlds check out http://learningwebgl.com/blog/?page_id=1217 where they go over it using WebGL.

Re: Notch trying jsFiddle

#36

Post by snprbob86 » Sun, Dec 02, 2012, 11:24 PM UTC

Pezmc wrote: post #24

Can someone dissect this code and explain what it does?

The first set of three nested loops is procedurally generating texmap, which is a multidimensional Array(16 * 16 * 3 * 16). 16x16 pixel textures, one for each the top, sides, and bottom, and then 16 of those. The inner loop tests against i, which is the current block "type" and performs customizations to the procedurally generated textures.

The next set of three nested loops is generating a random "world" with a tunnel cut out of it.

The renderMinecraft function is performing a minimal perspective projection http://en.wikipedia.org/wiki/3D_projection for a single ray cast into the world. Each pixel is cast and then, for each object hit by the ray cast, the closest is found, and a texture mapped pixel is calculated and written into the frame buffer.

Re: Notch trying jsFiddle

#37

Post by estel » Sun, Dec 02, 2012, 11:27 PM UTC

shocks wrote: post #33

setInterval(clock, 1000 / 100); Is there any reason for writing 1000/100 instead of 10? edit: Thanks guys!

It's a good way to remind you the figure is in ms, and easily manipulate the interval as a fraction of a second.

Re: Notch trying jsFiddle

#38

Post by anatoli » Sun, Dec 02, 2012, 11:27 PM UTC

shocks wrote: post #33

setInterval(clock, 1000 / 100); Is there any reason for writing 1000/100 instead of 10? edit: Thanks guys!

It just makes it clearer that he wants it to run at 100FPS: (1000ms / desired FPS)

The usefulness is more obvious when you want 60FPS, which is not easily represented without rounding.

Re: Notch trying jsFiddle

#39

Post by dag11 » Sun, Dec 02, 2012, 11:28 PM UTC

shocks wrote: post #33

setInterval(clock, 1000 / 100); Is there any reason for writing 1000/100 instead of 10? edit: Thanks guys!

It was probably for readability, i.e. "100 times per second".

Similarly, people will write (10 * 60 * 60) if the value is seconds and the programmer intends to indicate 10 hours.

Re: Notch trying jsFiddle

#40

Post by [deleted] » Sun, Dec 02, 2012, 11:28 PM UTC

ewolfe wrote: post #35

tgandrews wrote: post #4

Can anyone explain how this works? I never have got to grips with 3D.

It looks like he's using a matrix to create cartesian coordinates in a model-view space and then performing some basic linear algebra on the points to animate it. For a primer on 3D worlds check out http://learningwebgl.com/blog/?page_id=1217 where they go over it using WebGL.

[deleted]