Bubble Background Animation

I was pondering concepts for interesting web designs when the idea occurred to me that an animated bubble effect might lend a peaceful ambience to a webpage. I experimented with placing a Javascript-controlled SVG animation into the background of a page. You might like to judge for yourself whether this is successful or not (SVG-enabled browser required and a reasonably fast CPU recommended).

If you were around at the dawn of dynamic HTML you will probably have stumbled across amateur websites who thought it was really rather stylish to add a Javascript snow or bubble effect over the top of the page content.

Fortunately, those days are gone. By and large, it seems that amateur webmasters today know that just a nice colour scheme and a consistent, simple style trump a jumble of styles, javascript effects and stock animated GIFs that we all remember too well. Nice graphic design is done for you if you just install a blog and browse existing themes. Some may not even remember effects like this (Warning: Not safe for work or indeed any other time you require functioning eyeballs).

It's well-known that animations draw the user's attention in webpages. That doesn't mean we always want to avoid them: sometimes we want to direct the user's attention in one direction or another, particularly when the page is being updated dynamically with Javascript. This is not one of those special cases. Since the goal of this experiment is to build a fully-animated webpage, we will have to ignore that inconvenient little fact. However, this suggests we need to keep the animation as unintrusive as possible. Keeping it nice and slow may help, and it should certainly be in the background and not the foreground.

SVG is useful for this kind of effect because it has a feature (<svg:use>) for manipulating independent clones of a symbol. It is therefore simple to draw the original shape using an SVG editor, and the Javascript merely needs to manage instances of the clones.

Using Inkscape, I drew up a bubble looks like this:


There's a certain knack to drawing bubbles like this, of course. Air bubbles in water are colourless, but they are reflective due to total internal reflection. The amount of reflection increases as the angle of incidence increases, up to the critical angle, at which all light is reflected. At a water-air boundary the critical angle is 48.6° so actually the bubble should appear totally reflective from about 75% of the radius.

If this sends you into a bit of a panic as you struggle to remember your school physics lessons, don't worry. I'm not recommending a mathematically accurate implementation of Fresnel's Equations. With a lot of art (not just on computers), an appreciation of the physics can go a long way towards adding realism. But a 100% accurate simulation is not necessary for an effect to seem convincing - trial and error is much easier. The gradient as I've drawn it is not accurate but looks alright. Similarly, bubbles have two specular highlights corresponding to the water-air boundary and the air-water boundary.

As an aside, one day it may be possibly to depict fully reflective and refractive bubbles. Using SVG's incredible feDisplacementMap filter, you could distort the background using a pre-computed "lens" image. But that is unlikely to run at interactive speeds today, even if the filters required were fully and accurately supported, which they are not. The bubbles I've drawn are intended to be a compromise between rendering simplicity and attractiveness.

The bubble system (really just the SVG on its own) animates 20 clones of the bubble symbol. Again, this is based on some physical principles. The smaller bubbles are subject to less drag so have a higher terminal velocity, bubbles grow slightly as they rise and the pressure decreases and so on. One of the most effective things is that the bubbles drift with a random walk: they can randomly drift to one side or the other. They don't go straight up nor do they oscillate sinusoidally like the classic DynamicDrive script. For the most effective animation, bubbles would drift with the currents but this is simpler and reasonably effective.

I am quite pleased with the results. To really rid ourselves of the legacy of Javascript-animated GIF images, it would be important for this effect to tie in with the graphic design of the page, which I haven't shown.

I don't think this is realistically ready for production websites: Internet Explorer cannot display SVG, for one thing, and the intensive CPU requirement is also a problem. But I do think that sharp SVG graphics allow us to produce a wholly better standard of animation than what was possible before. With this, I think it's possible to make a bubble animation complement rather than detract from a web page.


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