by Charles Ying

Posts Tagged ‘graphics’

On Mobile Phone OS Design and GPUs

Wednesday, December 2nd, 2009

Mobile phones have really big screens.

Tablets will have even bigger screens.

If you want your mobile phone OS to matter in 2010, you’d better optimize for rendering graphics on the GPU.

GPUs are far more power efficient and faster at drawing graphics. As mobile device screens get really large, drawing the graphics “old school” on the CPU is moving from “unacceptable” to “impossible” pretty quickly.

Today, Motorola Droid runs at about half the frame rate of iPhone 3GS. The GPU in both is a PowerVR SGX 530 series chip.*

A PowerVR SGX 530 has a fill rate of 200 million pixels per second. That means Motorola Droid’s GPU could theoretically drive 8 full screen refreshes at 60 fps on a Droid-sized (WVGA) screen. All without the CPU’s help.

Parts of Android’s graphics subsystem seem to be GPU accelerated, but more is needed.

Imagine if the Android UX ran at a rock solid 60 fps. Then, I think we’d have something pretty sexy.

I wonder if Apple’s PA Semiconductor unit is designing GPUs instead of CPUs?

* It’s unclear what the exact model of the iPhone 3GS GPU is, and so the exact fill rate is not known… (though if it were, say, a PowerVR SGX 535, its fill rate would be 400 million pixels per second)

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Chocolux for WebGL = GPU raytracing in browser

Sunday, October 18th, 2009

I’ve just finished my port of Chocolux for WebGL (click for demo page).

Chocolux is a real-time recursive GPU raytracer using four spheres by Auld. Today, Chocolux now can run in your web browser.

The implications of this are pretty mind blowing. WebGL now allows compiled code to run on the GPU. Imagine what games, image processing, and applications will be possible with compiled shaders and general GPU computing (OpenCL?) now in the browser. And with WebGL gaining widespread adoption, it’s going to be here fairly soon.*

For more information about cutting edge fragment shader GPU raytracing and rendering, check out Rendering Worlds with Two Triangles (PDF).

*pending completion of a stable WebGL spec, naturally.

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Snow Stack is Here

Saturday, July 11th, 2009

What is Snow Stack?

A new 3D CSS Visual Effects demo using pure HTML, WebKit’s 3D CSS Effects extensions and JavaScript.

You can now see Snow Stack’s live demo if you have Snow Leopard and Safari. On Leopard, you can use WebKit nightly build 45754 or later for a slightly slower experience.


Click here to open the Snow Stack live demo. Arrow keys to move, “Space” to toggle magnify mode. Mouse click on an image to view on Flickr. You need to “right arrow” on the right wall to get more photos loaded in.

Many thanks to Simon Fraser for his help with performance profiling Snow Stack.

And yes, OS X Leopard with WebKit nightly will also do accelerated 3D transforms now, just like iPhone Safari.

Implementation Notes

  • Larger images load in after 2 seconds for high quality zoomed images.
  • State changes are handled via CSS.
  • Reflections use CSS masks instead of a Canvas draw (standard box reflections don’t quite work yet).
  • Reflections sit on a scaleY(-1.0) coordinate system and are tracked independently, which is surprisingly easy.
  • This demo pushed a few performance limits and currently avoids drawing and animating a drop shadow and border.
  • Animating transforms with a transform list must have only 1 function to animate in hardware.
  • Snow Stack’s 3D transforms, transform and opacity animations all run on the GPU. Layout and networked image loading happens on the CPU.
  • Key states are tracked manually (timers handle keyboard delay and repeats) so a smooth motion can be achieved when the keys are held down.
  • Cell sizes are chosen at initial window load time and don’t change on window resize, although the origin does. It’s rather slow, however, so I may end up changing that.
  • The computedStyle transform matrix is used to calculate how far away the dolly is from the target image, which is then used to assign a scaled rotation to the “camera”. Ideally, this might be done a different way, but the results are pretty good, and fast.
  • To give you a sense of the effort involved, this demo was written over 3 days, a few hours each evening.
  • Snow Stack’s source code is now available from the CSS-VFX project.

Other CSS Visual Effects Demos

Updates and iPhone Apps

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