Heading in the right direction with WebGL

Wednesday, October 12, 2011

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Editor's note: The Chromium WebGL team worked closely with the Maps team to help make MapsGL a reality. We invited a member of the Maps team to talk about their experience with MapsGL in the hope that it would help inform others who are interested in deploying a large scale WebGL app.

At this point it's almost hard to remember, but when Google Maps was first released in 2005, it was one of the first web applications to demonstrate what was possible with AJAX and the web platform. This project was a challenge technically but we’d like to think that it helped to fire the imaginations of web developers around the world.

Today, the Maps team is launching a beta of a brand new experience we call MapsGL. MapsGL is one of the first large scale applications to be built on top of WebGL. MapsGL makes use of 3D rendering and hardware graphics acceleration to provide an experience that is seamless, smooth, and runs directly in the browser.

Technically, MapsGL brings significant changes to how map and image tiles are rendered on the client and server. Rather than loading pre-rendered image tiles from servers, vector data for the map is sent to the browser and rendered on the fly using WebGL. This generally means that less data needs to be sent to the browser, but also that every aspect of the map needs to be rendered on the order of ~20ms per frame in order to achieve a reasonable frame rate. Imagery transitions in Maps are also enhanced by loading 3D metadata along with image tiles, allowing Maps to provide rich 3D transitions between different levels and angles of imagery.

While developing MapsGL, we found that WebGL draws from both native and web app backgrounds. For those used to working on web applications, WebGL adds a lot of functionality, but also increases the complexity of what you need to build and test. Even though WebGL is cross platform, performance varies dramatically across graphics hardware and operating systems - and what improves performance on one may hurt performance elsewhere - so testing across a wide array of setups is critical.

We also found that performance dependent Javascript and WebGL optimizations were needed in order for MapsGL to run properly on slower hardware. For example, there are a number of users with graphics cards that can't currently run WebGL content. In these cases, we don’t give the user the ability to opt-in and they can continue with the current Maps experience. Other graphics cards have somewhat poor performance for some key operations, which we measure with a small benchmark when the user first opts-in. In these cases, MapsGL falls back on a hybrid approach where we use pre-rendered raster tiles for the background of the map and only dynamically render labels on top of these.

We hope that MapsGL makes you excited to use WebGL in your own app. WebGL enables 3D graphics and immersive experiences in the browser that were formerly impossible. As WebGL becomes more robust and graphics card drivers improve, we can't wait to see what web developers will create with it. Check out the WebGL documentation and get started!

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