fill-extrusion-color data-driven styling error in v0.29

[ashleyclough]

3D maps that rendered correctly in v0.28 have odd colour shift in v0.29. The following works code works fine as type 'exponential' and 'interval' in 0.28 but has bizarre colour shift in the mid-range when default type 'exponential' in 0.29

"fill-extrusion-color": {
"property": 'density_per_km',
"stops": [
[2, "rgb(46,124,172)"],
[55, "rgb(77,165,177)"],
[132, "rgb(102,194,165)"],
[607, "rgb(171,221,164)"],
[1287, "rgb(230,245,152)"],
[1985, "rgb(254,224,140)"],
[2650, "rgb(253,198,118)"],
[3299, "rgb(253,174,97)"],
[3995, "rgb(244,109,67)"],
[4927, "rgb(213,62,79)"],
[7147, "rgb(158,2,66)"],
[10028, "rgb(128,1,10)"],
[12889, "rgb(69,1,5)"],
[40000, "rgb(34,0,2)"]
]
},

Expected Behavior

https://parallel.co.uk/3D/population-density/#10.2/53.7394/-1.6581/0/40

Actual Behavior

https://parallel.co.uk/3D/population-density/index29.html#10.2/53.7394/-1.6581/0/40

[mourner]

Interesting, @kronick could this be caused by your changes?

[ashleyclough]

Tried the same thing with HSL rather than RGB colours and there's still a difference between v0.28 and v0.29.

There's also a long-standing issue with HSL colours which is why I always use RGB - you can see the lack of yellows and oranges in the v0.28 version compared to the RGB. I used Photoshop's colour picker to convert between RGB and HSL.

"fill-extrusion-color": {
"property": 'density_per_km',
"stops": [
[2, 'hsl(203,73%,67%)'],
[55, 'hsl(187,56%,69%)'],
[132, 'hsl(161,47%,76%)'],
[607, 'hsl(113,26%,87%)'],
[1287, 'hsl(170,38%,96%)'],
[1985, 'hsl(44,45%,99%)'],
[2650, 'hsl(36,53%,99%)'],
[3299, 'hsl(30,62%,99%)'],
[3995, 'hsl(14,73%,96%)'],
[4927, 'hsl(353,71%,84%)'],
[7147, 'hsl(335,99%,62%)'],
[10028, 'hsl(356,99%,50%)'],
[12889, 'hsl(356,99%,27%)'],
[40000, 'hsl(356,100%,13%)']
]
},

HSL v0.28
https://parallel.co.uk/3D/population-density/index28hsl.html#10.2/53.7394/-1.6581/0/40

HSL v0.29
https://parallel.co.uk/3D/population-density/index29hsl.html#10.2/53.7394/-1.6581/0/40

[ashleyclough]

Is it possible that an issue with the interpolation between HSL colours may be the hue value passing through 0/360 degrees? You can go either way between green and orange: the quick way via the yellows or the long way via the purples, passing through the 0/360 threshold.

[mourner]

@ashleyclough thanks for the details! If you want to help out further with this, try reproducing the difference in an isolated form using just the mapbox-gl-function module, and then doing git bisect to find the offending commit that changed the behavior.

[kronick]

@mourner - yes, very possible this is in my binary search changes. I'll look into it today.

[mourner]

@ashleyclough we found the bug and submitted a fix (mapbox/mapbox-gl-function#35) so no need to investigate further.