Have a play

You can try out JSFractal here.

What is it?

JSFractal is a web-based tool (written entirely client side in JavaScript) to allow you to explore fractals. Currently, only the Mandelbrot set is implemented but I hope to add support for switching to Julia sets and other types in the future.

You can drag-select on the fractal to choose an area to zoom in to. As you progress, you can see a timeline of previous points of the fractal, allowing you to switch to any prior state and continue in a different direction.

As well as allowing you to see previous states of the fractal, the timeline also supports a playback feature so you can watch the entire transition you’ve created zoom from start to finish.

At any point you can change the quality settings and size of the rendered fractal. Please note however, the higher the quality and the larger the fractal size - the longer you’ll wait! Currently there is only one colour scheme to choose from.

Finally, you can bookmark the page at any point. Returning to the URL will render the fractal that was showing at the point you bookmarked the page.

Have a go!.

Why?

With the current JavaScript performance arms race going on between V8, Webkit, Mozilla and Opera, I wanted something fun to write that would really push the browsers to the limits.

After picking up James Gleick’s Chaos again, my interest with fractals was renewed and hence this project. Obviously this isn’t the best medium for something as computationally heavy as a fractal exploration tool - but what the hell. It’s a good experiment!

On a reasonably spec’d machine and one of the pre-release ultra-mega-crazy-fast JavaScript engines it’s actually pretty usable. There’s a few tricks used along the way to boost performance which I’ll go into later.

How does it work?

Overview

JSFractal is written entirely in JavaScript with no server side components. It uses MooTools 1.2 and the canvas element. Thus, Internet Explorer need not apply. Sorry! I attempted to patch in support with Google’s ExplorerCanvas but it was so ridiculously slow that I had to drop it.

Compatibility

It has been tested and is thought to work in the following browsers:

• Mozilla Firefox 1.5+
• Safari 3+
• Opera 9
• Google Chrome

For reference, best performance is currently with Firefox 3.1 beta (with JIT JavaScript enabled) and Google Chrome.

Rendering techniques

Every time a fractal is generated, each pixel’s value needs to be calculated. On top of this, each pixel needs to be drawn individually. This means the key to fast performance is:

• Efficient calculations for each pixel
• Fast drawing to the canvas

I refined the fractal calculations as much as possible and had it running pretty fast. However, the actual rendering to the canvas proved to be a little trickier to speed up.

Initially I implemented rendering using the fillRect method of the canvas object to draw each pixel as a 1×1 rectangle. This … is … unsurprisingly … slow. There is a lot of overhead in setting up and executing each call (setting fillColor etc.). This meant, particularly on the faster JS engines, the bottleneck was primarily the rendering.

I love createImage(). This is a canvas method implemented in Firefox 3+ (and recent Webkit nightlies I believe) which returns an updateable pixel buffer object. This means we can call it once at the beginning of a render to retrieve access to the pixel buffer and write RGBA values directly (it’s implemented, effectively, as a single dimensional array so access is fast). It can then simply be redrawn back to the canvas at the end. Fast!

The above is great, but not all the current canvas supporting browsers have this method. The spec for it is still somewhat in the air. There’s debates as to quite what it should return - the number of pixels does not always equal the canvas size etc. (at least, in theory). In effect, this means that Chrome and Opera are both missing this method which means the only option is fillRect.

It seemed a great shame that Chrome, despite having a very fast JS engine, was lagging behind Firefox merely because of the awful fillRect() method of rendering.

After posting a comment to an unrelated article on a Spectrum Emulator on Ajaxian, cromwellian suggested the possibility of constructing DataURLs manually as an alternative.

DataURLs?

Using DataURLs is actually crazy enough to work. And, even better, it’s pretty fast. It effectively builds up a bitmap image file on the fly, draws it to an Image object and finally draws the loaded Image to the canvas. The great thing about this technique is that it’s shifting the performance burden from the canvas element to the JavaScript engine. And since the current crop of browsers are getting pretty rapid in this area, it isn’t too much of a performance hit.

Measurements in Firefox 3.1b showed only about a 40% hit for using the DataURL method of rendering compared to writing directly to the pixel buffer. This sounds a lot but compared to fillRect() it’s a great improvement.

All three rendering methods are included in JSFractal (the most appropriate is chosen dependent on your browser features). Note: The fillRect() implementation is never actually used since the only browser than I know of that would require this is Internet Explorer.

Issues

There are a few issues I’d like to address which I’ll go into here.

Colours

Currently there is only one colour scheme available. What’s more, it’s not the most optimal algorithm for producing the prettiest fractals. I’d like to improve this - it’s more evident the deeper into the fractal you go (differentiations in colour become less, leading to large blocks of the same colour). Best results happen when the quality level is whacked up high and the size is set to the maximum.

Changing settings and the timeline

Changing the settings (size, quality, colours) half way through a fractal exploration will only update the current fractal. The timeline playback etc. will still function but previous fractal states may be stretched to fit meaning the animation may change in quality during playback.

There’s not a lot I can do about this, however, since I’d need to re-render all previous fractals which would be an unacceptable performance hit. I think the current solution of allowing you to change settings mid-way through and doing its best to compensate for the change is the current best compromise.

Credits

• Parts of the bitmap and base64 encoding methods adapted from Neil Fraser’s JavaScript BMP library.
• cromwellian for his DataURL idea.
• Graphics heavily inspired by kailoon’s Photoshop tutorial.

Over and out

Any feedback, bug reports or ideas for improvement very much appreciated.

I wrote the game a couple of years ago now (mostly as an experiment with JavaScript) and didn’t really plan to promote it particularly but it’s great to see around 15 new players a day having a go!

It recently passed the 500,000th game played - around half of those games were actually completed (a score was submitted). From a quick scribble on the back of a Topman receipt (taking a rough average of 2 minutes per game) this means there’s been about 1 man year of procrastination play so far

Well done to Joe Bloggs 6140 for the current high score of 5,510. The average score is 1981.98 across all the games completed.

The booby prize goes to Joe Bloggs 2681 for achieving the lowest score of just 152. It’s actually quite a feat to achieve such an abysmal score - seriously, try it. It’s not as easy as it looks!

At the time of writing not everything’s fully worked out (issues with the headphone socket etc.) but it’s a good way to get the stock Hardy 8.04 install functional and on the net.

For the most basic install (to get wireless working at least) you can just copy a couple of debs onto a usb stick and “dpkg -i *” install them before getting the rest of the updates via the net repository.

Up to date discussion of progress currently available in this thread.

Not a lot of planning went into this one (read: no planning went into this one) so the production qualities may, unfortunately, rule this out for a BAFTA. That, and the plagiarised unlicensed soundtrack.

Here’s a better quality version encoded in DivX (right click/save as to download - roughly 21mb).

Those with epilepsy should probably give this one a miss!

This quick guide shows how to use Samba to achieve the same aim. It is aimed at Ubuntu users but (the general concepts at least) should work on any modern Linux distribution. It is also written with a Windows XP guest in mind but a similar process should work in Windows Vista, Windows 2000 and other operating systems.

The goal is to set up a network share which both operating systems can transparently read and write to.

For reference, I am using Ubuntu 7.04 (Feisty).

Which VMware?

I’ll presume you have VMWare already installed with a Windows XP guest virtual appliance already set up. This guide is aimed at users of VMware Player and Server editions (I am using VMware Player).

VMware Player is a simple:

sudo apt-get install vmware-player 

away. For the Server edition, you’ll probably want to consult the wiki.

Install Samba

If you don’t already have Samba installed, now would be a good time to do it:

sudo apt-get install samba

In order to keeps things clean and easy to manage, we’ll set up a new user account to own the share. This account name will be used when connecting to the share from within Windows. For the purposes of illustration, I will be creating a share called sandbox with the username and group also being sandbox.

Create the new group and user account with no login privileges:

sudo groupadd sandbox
sudo useradd --gid sandbox --shell /bin/false sandbox

To avoid creating a redundant home directory, you can add:

--home /nonexistent

to the end of the previous command.

Now you need to add a matching Samba account. You’ll be prompted to set a password - make note of this as this is what you will use to connect to the share from within Windows.

sudo smbpasswd -a sandbox

Next you’ll need to create a directory to be used as the share (assuming you don’t already have one). Create a directory, setting the username to your usual login and group to sandbox. Then chmod the directory 775 (assuming you wish both yourself and the virtual appliance to have read/write access). Here is what I entered:

cd $HOME
mkdir sandbox
sudo chown russ:sandbox sandbox
sudo chmod 775 sandbox

When you write to the share from within Ubuntu, new files will be created with the default permissions 644 with the username and group being your own user account. When your Windows client connects to the share, it will access it as if it were the local system user sandbox and so the group permissions will apply and you won’t be able to write to any files created from within Ubuntu.

To get around this problem, we can set the groupid bit for the sandbox directory which means all new files created will inherit the permissions of the parent and so the sandbox user from within Windows will be able to make read and write changes as desired.

sudo chmod g+s sandbox

If you don’t understand the above, don’t worry, just chmod the directory with the command above and all should be well.

Setting up the Samba share

Now all that’s left to do is to tell Samba about our share. Open up /etc/samba/smb.conf in your favourite text editor.

sudo gedit /etc/samba/smb.conf

Firstly, we need to set the security mechanism to user. Look for the line:

security = user

and make sure it is uncommented (remove the preceding semicolon if there is one).

Now, scroll down to the Share Definitions section and add the following:

[sandbox]
path = /home/russ/sandbox
valid users = sandbox
read only = No
create mask = 0777
directory mask = 0777

Be sure to set the correct path to your share. Save the file and restart the Samba daemon:

sudo /etc/init.d/samba restart

That should be it. You should now be able to connect to your share from within the Windows guest. At this point you need to know what IP address to connect to from within Windows. This depends on what networking mode you are using for your virtual appliance.

Bridged Networking

In this mode, your guest OS has its own IP address and so the address it needs to connect to is your usual host machine’s address. In this case your address is probably the top line from the output of this command:

ifconfig | grep "inet addr:"

NAT networking

In this mode, your guest OS shares your host’s address (in terms of other machines on the LAN) and communicates with the host via a private network. In this case, the IP address you need to connect to is most likely the bottom one from the output of this command:

ifconfig | grep "inet addr:"

Connecting to the share from within Windows

If you are unsure as to your host’s IP address, try and ping it first from within the Windows guest to confirm you have the right one.

Having worked out what IP address to connect to, you should now be able to connect to your share from within Windows.

The easiest way to do this is:

1. Open up My Computer
2. Go to the Tools menu and then Map Network Drive
3. Choose a drive letter to map the network share to
4. In Folder, enter: \\HOSTIP\sandbox (replacing HOSTIP)
5. Click “Connect using a different user name” and enter:
   • username: sandbox
   • password: yourpassword
6. Click OK and then the Finish button to connect

Hopefully, congratulations are in order. If not, be sure to make sure that any firewalls you have running (host or guest) have the correct rules set to allow communication between the two systems.

A note on security

At this point, assuming you have a successful connection, it is worth noting that any other machine on your local network (and potentially the internet if you are not behind a NAT or firewall) can connect to your share (assuming they have the correct credentials).

If you are only using Samba for sharing with VMware (as I am), you may wish to restrict access to VMware only. This is quite easy to do since VMware creates virtual network interfaces for communication between hosts and guests. This means we can set Samba up to ignore any communications that do not originate from these interfaces.

To do this, open up your Samba configuration file again:

sudo gedit /etc/samba/smb.conf

Make sure you have a:

bind interfaces only = true

line and that it is uncommented (remove any preceding semicolons). Just above this should be an interfaces line (most likely commented out). Add the following just below this:

interfaces = vmnet0 vmnet1 vmnet8

These are the virtual interfaces VMware uses for each type of virtual networking: bridged, host only and NAT respectively.

After making the changes, you will need to restart Samba again:

sudo /etc/init.d/samba restart

and possibly shutdown your VMware session and restart the VMware service:

VMware Player:

sudo /etc/init.d/vmware-player restart

VMware Server:

sudo /etc/init.d/vmware restart

Finished

You should now have a Samba share configured which is only accessible from your VMware guest appliances. Good luck!

New features include:

• More high scores shown (top 30 now rather than the original top 5)
• ‘Replay’ feature - watch any game currently in the top 30
• New theme “alternate” - it’s ugly, but it might help people who have trouble with red/blue/green

“Tap Trap” is a puzzle game written in Javascript. It was born after a lengthy battle with an addiction to the puzzle game Same GNOME. As a standard client application Same GNOME (distributed with the Gnome desktop environment) is great but I wanted a version that could be played online - complete with public high score tables and taking advantage of the global accessibility that the internet provides.

This is a playable version 1.0.

More information on the Tap Trap project page.

There are two sins for which I am consistently guilty and wish to address:

1. Frequently coming across, and promptly forgetting, useful tidbits of knowledge - either from others or items I’ve stumbled upon myself.
2. Leaving random projects I’ve done to languish on a CDR never to see the light of day again.

So this is what 2tap.com shall become. Random software, web and technology interests with the odd project to share for good measure. Primarily for myself but also for anyone who can glean anything useful.

To sumarise, it’s geek stuff without the angst and political agendas. Well, mostly!