So let's be clear about something right from the very start: I'm not a physics guy. I love me a good physics engine, but I will likely never build one because that's just not where my expertise lies. Far be it from me to criticize the algorithms used by your broadphase collision pass, because I only have the most high level of ideas what that actually is. I'm a graphics guy through and through and that's where I'm happy to stay.
However, I do know a thing or two about writing fast Javascript code, which is something that will become fairly important to the new breed of browser-oriented physics engines that are starting to crop up, like Ammo.js, Cannon.js, and the various Box2D ports. Unfortunately, however, I've seen a few common threads within these engines that I think will limit their effectiveness in real-world use, and I wanted to get some of it off my chest while the development of these libraries is still in the early days. Some of these trends are inherited from the underlying C++ libs these libraries wrap (like Ammo.js, which is built from Bullet with Emscripten), but others appear to be self imposed. That's the group I'm talking to.
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Thursday, April 5, 2012
If I built a physics engine...
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Friday, March 23, 2012
Javascript memory optimization and texture loading
Over the past couple of weeks I've seen a few great resources about optimizing your javascript. One is a wonderful GCD presentation by Lilli Thompson about best practices when writing code for V8 (Chrome's Javascript engine.) Although the presentation uses Chrome for it's concrete examples, much of the information is very practical for any browser.
GDC 2012: From Console to Chrome
It's a long presentation, but well worth the time. If you simply can't bring yourself to sit and listen for a bit, though, at the very least take a look through her slide deck.
The second resource is a great blog post by Ashley Gullen of Scirra about reducing the amount of time your app spends in that dreaded garbage collecting coma.
How to write low garbage real-time Javascript
I highly encourage you to go through both of those if you are a web developer. Even as an expert dev with years of experience, I'm sure you'll learn something!
GDC 2012: From Console to Chrome
It's a long presentation, but well worth the time. If you simply can't bring yourself to sit and listen for a bit, though, at the very least take a look through her slide deck.
The second resource is a great blog post by Ashley Gullen of Scirra about reducing the amount of time your app spends in that dreaded garbage collecting coma.
How to write low garbage real-time Javascript
I highly encourage you to go through both of those if you are a web developer. Even as an expert dev with years of experience, I'm sure you'll learn something!
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Wednesday, March 14, 2012
Anisotropic Filtering in WebGL
On Google+ this morning Ilmari Heikkinen pointed out that support for the EXT_texture_filter_anisotropic WebGL extension landed in Webkit a little over a week ago. That's awesome, as it's one of the features that I've been waiting for essentially since I first started playing with WebGL.
[Update: To give credit where credit is due I've had several people point out that Firefox had this feature first. Guess I need to follow their commits more closely! Also, while some of the appropriate code is in Chrome I guess the feature isn't officially part of the browser yet. Apparently the fact that it works at all is something of a happy fluke. So I guess that for the time being Firefox is the only browser that actually supports this!]
[Update: To give credit where credit is due I've had several people point out that Firefox had this feature first. Guess I need to follow their commits more closely! Also, while some of the appropriate code is in Chrome I guess the feature isn't officially part of the browser yet. Apparently the fact that it works at all is something of a happy fluke. So I guess that for the time being Firefox is the only browser that actually supports this!]
I put together a really simple demo this morning to show how it works, and if you've got a recent Chrome dev build or Firefox nightly you should give it a try!
Yeah, the demo is ugly but it shows off the effect nicely. For those of you not familiar with the concept, Anisotropic Filtering is an extension of standard mip-mapping techniques that improves the quality of textures when viewed at an angle. A good example of this is the floor and ceiling of the demo above. With standard trilinear filtering (gl.LINEAR_MIPMAP_LINEAR) as the floor gets further away from you it becomes blurry pretty quickly:
By using anisotropic filtering, we alter the way that the mipmaps are queried in scenarios like this one, which can give a much crisper, cleaner image:
There is a performance penalty associated with enabling this, and when you do enable it you can specify how many samples are taken for a performance/quality tradeoff. This has become a pretty common setting available for the user to toggle in PC games, and so it's great that we're now able to take advantage of it on the web too!
Implementation
Turning this feature on is pretty simple in a supported browser. As with compressed textures the first thing we do is query the appropriate extension to see if it's available:
var ext = gl.getExtension("MOZ_EXT_texture_filter_anisotropic");
Obviously with Chrome you would query with WEBKIT_ instead of MOZ_, and eventually the prefix should go away entirely. If it returns null the extension is not supported and we move on, doomed to a life of blurry walls. If it is supported, however, it will return