1. OL3 A unique mapping library

2. Draw early, Draw often

3. So for good rendering quality: vectors redrawn at each frame while interacting and animating at 60 fps!

4. Performance challenge!

5. Now let's look at the techniques we use in the library

6. #1 batching Minimize data processing and manipulation: style calculations geometry simplifications R-tree lookups object creations replay batch during animations/interactions

7. #2 geometry simplification Douglas Peuker (lines) Quantization to maintain topology (polygons) also allows for better rendering qualtity

8. #3 over-simplification Over-simplification and clipping for the parts that are outside the viewport.

9. (complex and large features)

10. #4 No intermediate canvas for vectors Vector geometries are draw to the output canvas directly. avoid composing transparent pixels save memory Consequence: vector layers are very cheap!

11. Feature Hit Detection

12. (hit detection)

13. Hit Detection Canvas doesn't natively support hit detection. Technique used: redraw the entire "scene" in a 1x1 px canvas, and test if there is a color. Advantages: features under others are detectable pixel-perfect detection tolerance for line detection on touch devices

14. WebGL

15. WebGL WebGL is now everywhere even in iOS! (iOS 8) allow to do thing otherwise not possible