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PERFORMANCE.md

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Performance

What's done & why in terms of performance.

IDEAS

  • combine canvases
  • render items of same style at once
  • delete and redraw animated objects
  • split off animated shadows
  • combine simple buildings in low zoom
  • use web workers for data processing
  • adapt features dynamically
  • pre-calc face direction
  • consider using a render queue
  • style lookup index

Projection cache

Looks like this has been a bad idea - removed. Probably develop the concept into rendering pipelines. (http://jsperf.com/projcache)

Readable keys (for compact data structures)

Seemed to be a good idea making these a bit more readable. Loss expected but turned out to be a slight gain. http://jsperf.com/readable-keys/2 TODO: Not true anymore. Refactor to objects/properties. DONE

Combined 2d faces

iPhone4, iOS5: seperate faces are 56% slower MBA 2010, Chrome: combined faces are 68% slower Staying with combined so far, probably add system detection. (http://jsperf.com/canvas-polygon-combiner)

Typed arrays

Using slice() is not worth it, but it turned out dropping some typed arrays is a good idea. Especially when these are created on each rendering pass. (http://jsperf.com/slice-access)

Canvas anti alias

While looking slick, it eats performance. Not so on iPhone4, iOS5: it doesn't matter MBA 2010, Chrome: anti alias is 24% slower Node: for any test, stroking lines eats ~60% performance (http://jsperf.com/canvas-anti-alias)

Math round

Using ~~ for a while, it turns out, bit shift << 0 is even faster. iPad4, iOS6: 12% faster MBA 2010, Chrome: 25% faster (http://jsperf.com/math-round-vs-hack/3)

Public methods vs. closure(d) functions

Huge gain for methods on desktop browsers vs. Safari (mobile). Will stay a bit until mobile catches up. Finally, Safari 6 mobile beats it too. http://jsperf.com/osmb-method-vs-function

Considerations for further performance improvement

degrade instantly, increase slowly (take average score of a few passes)

FADE IN

  • NO_STROKES
  • NO_SHADING
  • NO_SHADOWS_SCALE
  • NO_SCALE

MOVE

STATIC

  • NO_STROKES
  • NO_SHADING
  • NO_FLAT
  • NO_SHADOWS

http://jsperf.com/osmb-hidden-canvas4