1. OL3
A unique mapping library

5. « Draw early, Draw often »

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

7. Performance challenge!

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

9. #1 batching
Minimize data processing and manipulation:
style calculations
geometry simplifications
R-tree lookups
object creations
⇨ replay batch during animations/interactions

10. #2 geometry simplification
Douglas Peuker (lines)
Quantization – to maintain topology (polygons)
⇨ also allows for better rendering qualtity

11. #3 over-simplification
Over-simplification and clipping for the parts that are outside
the viewport.

12. (complex and large features)

13. #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!

14. Feature Hit Detection

15. (hit detection)

16. 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

17. WebGL

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