Under the Covers: Let It Snow…

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Under the Covers: Let It Snow…

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With one of those rare Seattle snowstorms underway today, I feel this is a great time to publish this description of our Holiday 2011 Test Drive demo “Let It Snow.” —Editor

When a browser effectively uses the underlying hardware, the possibilities are limitless. Over the holidays we released a demo that helps showcase the advantages of a fully hardware-accelerated, touch first browsing experience with Internet Explorer 10. This post takes a closer look at how the Let It Snow demo was created. The patterns in this demo are typical of the HTML5 experiences emerging across the Web today and early Metro Style Apps. We’ll take a look from a functional point of view, rather than visual.

As low power mobile devices and touch first user experiences become mainstream, customer expectations around browser performance are quickly expanding. Browser performance now includes how smoothly the Web site moves under your finger, how quickly the Web site responds to touch interactions, and how efficiently the browser consumes battery. With Internet Explorer 10 and Windows 8 we set out to build the world’s fastest browser for real world scenarios.

Building Let It Snow

We start with a themed postcard which contains a designated area for the holiday greeting.

Holiday Postcard

We start with a themed postcard which contains a designated area for the holiday greeting. The postcard is generated at runtime using HTML5 canvas and uses many common drawing techniques including drawing images, composing gradients, manipulating opacity and skew, and more.

We next add lots of falling snowflakes to create a snowstorm.

Animated Snowstorm

We next add lots of falling snowflakes to create a snowstorm. We do this using a second canvas that���s layered over the postcard. Each snowflake is represented as an object in a JavaScript collection which holds the state of the snowflake, such as current location, velocity, and the image to draw. The canvas is cleared each frame and the scene recreated from the underlying model.

Over time snowflakes will collect on the sign.

Snowflakes Collecting

Over time snowflakes will collect on the sign. Using hit testing techniques we determine when the snowflake is over the sign and then randomly assign the snowflake a target on the sign. As the snowflake approaches the target we use HTML5 Canvas composite modes to compose the snowflake on the canvas.

Snow can be brushed off the postcard using your finger or mouse.

Brushing Away the Snow

Snow can be brushed off the postcard using your finger or mouse. We track the user input through the new MSPointer event which enables a single consistent API across different pointer models. This allows us to provide a great multitouch experience in Internet Explorer 10 running on Windows 8. We use these captured points to erase portions of the canvas, creating the illusion of the snow being brushed away.

When the layers are combined they create an interactive holiday scene.

Complete scene

When the layers are combined they create an interactive holiday scene. The patterns used in this demo represent techniques commonly found in games such as Angry Birds or Cut The Rope, including script based animations, sophisticated user input, physics based game logic, and more.

We’re excited about the fast and fluid interactive experiences that can be achieved in Internet Explorer 10 and Windows 8 with a fully hardware-accelerated and touch enabled HTML5 platform. There’s no better way to experience these benefits than first hand through the Windows 8 Developer Preview.

—Bogdan Brinza‎, Program Manager, Internet Explorer

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