Road animation should be directional

[nvkelso]

• If it's a oneway road, all animation in one direction (as it is now, but confirm it'll go the "right" direction)
• If it's not a oneway road, then the animation should go 2 directions (like in v1)

[patriciogonzalezvivo]

this trick needs some changes on the layer. The oneway yes/no is passed as a 'color:'

Look here: https://github.com/tangrams/tangram-sandbox/blob/gh-pages/styles/tron.yaml#L37-L43

Then in the shader we interpret the red color as bidirectional:

https://github.com/tangrams/tangram-sandbox/blob/gh-pages/styles/tron.yaml#L139-L148

[patriciogonzalezvivo]

I'm in cross road with this one (see what I just did there ; )
To do one/not-one way roads here I need to add this JS function on the road colors

layers:
    roads:
        data: { source: mapzen }
        draw:
            lines:
                order: 2
                width: 5px
                color: |
                    function() { 
                        if (feature.oneway) {
                            return [0.,1.,0.];
                        }
                        return [1.,0.,0.] 
                        }

Then in the shader "read" the red channel (or any other) and apply something like this . What's the problem?
Using the color pass data between JS and GLSL, makes the color not useful anymore... it over rides it. That in the old tron was solve by hardcoding the color on the shader. I can do that but first we need to simplify and unify this color transitions, if it's possible to one single color... or (if is not possible) a transition between color A and B using the function-zoom:

https://github.com/tangrams/tron/blob/gh-pages/layers/roads.yaml#L71
https://github.com/tangrams/tron/blob/gh-pages/layers/roads.yaml#L210
https://github.com/tangrams/tron/blob/gh-pages/layers/roads.yaml#L229
https://github.com/tangrams/tron/blob/gh-pages/layers/roads.yaml#L272

Here is an example of how hardcoding all the animated roads between COLOR_A: vec3(0.418,0.754,0.736) (for zoom 8) and COLOR_B: vec3(0.086,0.135,0.260) (zoom 13) will look like:

https://mapzen.com/tangram/play/?scene=https%3A%2F%2Fgist.githubusercontent.com%2Fanonymous%2Fb2addb1ee3ab51a6e635f3a7b397aa56%2Fraw%2Fe253d14b7c9ad1bc27ef427d254258426992d8fb%2Fscene.yaml#15.8243/40.7108/-74.0068

@sensescape What do you think? Should I proceed?

Note: this should not add to much GPU processing power...

[patriciogonzalezvivo]

@sensescape @nvkelso should I proceed w this changes?

note: is a destructive change... will to all roads to have a two points (A -> B) gradients and all other color rules for them will be lost

[sensescape]

hmmm not sure, lots of details got lost: line widths look different, road casing is not visible, previous color work and the glow

z12
original:

with change:

z14
original:

with change:

[patriciogonzalezvivo]

@sensescape it's possible to tweak the colors to match what it was

Colors A -> B are here in lines 12-14

Zoom for A and B are in lines 8-13

[patriciogonzalezvivo]

@bcamper helps me with this different approach (abbaf7e) that relays on filter logic (which already is very complicated)

[patriciogonzalezvivo]

[nvkelso]

Verified the directions are now correct for 1 way and 2 way roads (looking at SF).

[nvkelso]

@patriciogonzalezvivo If no more work is planned for this, please close issue.