Meetar/line offsets #547

meetar · 2017-04-17T15:33:24Z

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meetar · 2017-04-17T15:39:10Z

This technique works pretty well for a constant offset, with one caveat – in places where multiple points create a curve with a radius r, if the offset is larger than r the curve will become inverted:

So the style would have to ensure this doesn't happen by setting appropriate offsets at various zoom levels.

As I understand the situation there isn't really any way around this without some kind of smarter context-aware clipping algorithm à la Clipper or this paper, neither of which would be ~easily compatible with our vertex shader… but I'm happy to be proven wrong :)

nvkelso · 2017-04-17T19:17:53Z

We use Clipper for some geom validation tasks in Tilezen.

Love this illustration :)

bcamper · 2017-05-12T18:37:08Z

demos/test.json

@@ -0,0 +1,30 @@
+{


We should remove test files from final PR

bcamper · 2017-05-12T18:37:19Z

demos/test2.json

@@ -0,0 +1,98 @@
+{


Ditto let's not merge test files

bcamper · 2017-05-12T18:37:34Z

src/gl/render_state.js

@@ -21,7 +21,7 @@ export default class RenderStateManager {
        this.defaults = {};

        // Culling
-        this.defaults.culling = true;
+        this.defaults.culling = false;


Need to turn culling back on

bcamper · 2017-05-12T18:46:17Z

src/styles/lines/lines.js

@@ -237,6 +241,7 @@ Object.assign(Lines, {
        draw.width = StyleParser.createPropertyCache(draw.width, StyleParser.parseUnits);
        draw.next_width = StyleParser.createPropertyCache(draw.width, StyleParser.parseUnits); // width will be computed for next zoom
        draw.z = StyleParser.createPropertyCache(draw.z, StyleParser.parseUnits);
+        draw.offset = StyleParser.createPropertyCache(draw.offset || 0, StyleParser.parseUnits);


If we are going to only accept px units (which I think we decided on), we should enforce that, probably here (first time the parameter is processed). Will need to double-check, but I think we should be able to do that by checking (if draw.offset isn't null) that draw.offset.value.units === 'px', and if not, log a warning and setting draw.offset to null. We may also want to add the ability to specify different default units for parseUnits though, so that offset values can have pixels as default units (if we decide we want that).

bcamper · 2017-05-12T19:16:07Z

src/styles/polygons/polygons_vertex.glsl

@@ -30,6 +30,8 @@ attribute vec4 a_color;
    // z:  half-width of line (amount to extrude)
    // w:  scaling factor for interpolating width between zooms
    attribute vec4 a_extrude;
+    // xy: direction of line, for getting perpendicular offset
+    attribute vec4 a_offset;


offset is only a vec2

bcamper · 2017-05-12T19:17:13Z

src/styles/polygons/polygons_vertex.glsl

-        // Adjust line width based on zoom level, to prevent proxied lines from being either too small or too big.
-        // "Flattens" the zoom between 1-2 to peg it to 1 (keeps lines from prematurely shrinking), then interpolate
-        // and clamp to 4 (keeps lines from becoming too small when far away).
+        vec2 offset = a_offset.xy; // values have an 8-bit fraction;


I think 8-bit fraction comment is no longer accurate since we're not multiplying/un-multiplying this value anymore

bcamper · 2017-05-12T19:17:32Z

src/styles/polygons/polygons_vertex.glsl

@@ -77,27 +79,36 @@ void main() {
    vec4 position = vec4(a_position.xy, a_position.z / TANGRAM_HEIGHT_SCALE, 1.); // convert height back to meters

    #ifdef TANGRAM_EXTRUDE_LINES
+        // vec2 extrude = a_extrude.xy / 256.; // values have an 8-bit fraction


remove old line

works w/miter joins + butt caps, not w/round/bevel join or round/square caps

bcamper · 2017-05-15T01:51:33Z

src/builders/polylines.js

+
+    if (cross) { // ccw bend
+        // pivot
+        addVertex(coord, Vector.neg(eC), false, uC, context, -1);


Bevel joins are broken - expected third parameter of addVertex() should be the offset vector (line's 2d normal), but it's being set to false here (not sure what the correct vector value should be).

bcamper · 2017-06-20T22:30:43Z

Follow-up work in:
meetar/line-offsets...premultiply-width
premultiply-width...mesh-variants

bcamper · 2017-10-02T18:07:14Z

Merged to master via mesh-variants-rebase branch

🎊

meetar · 2017-10-19T20:24:36Z

Merged to master via mesh-variants-rebase branch

Prepping the docs for this – is there an associated PR or commit I can refer to?

bcamper · 2017-10-19T20:31:54Z

It's all internals beyond the line offsets themselves. (Separately there's related work for specifying texture and line dash patterns in draw blocks, but I think we already covered that for docs elsewhere.)

This was referenced Apr 19, 2017

Calculate line offset for transit route relations tilezen/vector-datasource#1189

Open

BLOCKED: Offset transit lines per tile attribute tangrams/bubble-wrap#245

Open

bcamper reviewed May 12, 2017

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demos/test.json Outdated

@@ -0,0 +1,30 @@

{

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We should remove test files from final PR

bcamper reviewed May 12, 2017

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demos/test2.json Outdated

@@ -0,0 +1,98 @@

{

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Ditto let's not merge test files

bcamper reviewed May 12, 2017

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bcamper and others added 19 commits May 12, 2017 15:25

line offset in shader WIP

b49e70d

works w/miter joins + butt caps, not w/round/bevel join or round/square caps

comment

b9f8472

1 triangle

593b32e

rotate extrusion vectors for round joins

a411e88

test style

fce725c

test geo and style

801a0f1

comments, tests

26d5f34

rotate

63ee1ca

perpendicular offset

1bee9e3

add a_normal

5d9156e

attach line normals

859e0d4

set isCap flag in normal.z

3731764

vector = angle and distance

ccf5cdb

more complex test

4087a0b

restore original square cap code

4f59f8d

flip bevels

a79f462

comment and cleanup

ef39427

aka the normal

cc4fe4d

test right angles

e5910d2

meetar and others added 14 commits May 12, 2017 15:33

normals already normalized

a40898d

reset outgoing vectors

c904ea3

apply offset to all vertices

6b68867

offset line start with next join's mitervec

07f9916

update subway map demo

cfaf11a

cleanup

c0ab3c5

parse styles

2b1caae

premultiply offset distance

96444a3

offsets in px only, normalize not needed

67702dc

offset_normalize is unneeded

4d1b005

remove test files

0a41dc8

restore culling

1417af2

offset is a vec2

07ae27f

cleanup

d4f34c5

meetar force-pushed the meetar/line-offsets branch from a4f548f to d4f34c5 Compare May 12, 2017 19:35

meetar and others added 4 commits May 12, 2017 15:42

cleanup unused variables

a3bb328

small line builder improvements

a5cefcb

line outline inherits line offset

58c4aed

fix square line caps

a84f036

bcamper reviewed May 15, 2017

View reviewed changes

meetar and others added 2 commits May 15, 2017 11:43

use addFan for bevels

367df3e

lint

ad147c6

bcamper added this to the v0.14.0 milestone Jun 20, 2017

bcamper closed this Oct 2, 2017

bcamper deleted the meetar/line-offsets branch October 2, 2017 20:46

tallytalwar mentioned this pull request Apr 24, 2018

Implement line offset to be with parity with Tangram JS tangrams/tangram-es#1796

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Meetar/line offsets #547

Meetar/line offsets #547

meetar commented Apr 17, 2017

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meetar commented Oct 19, 2017

bcamper commented Oct 19, 2017

Meetar/line offsets #547

Meetar/line offsets #547

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meetar commented Apr 17, 2017

meetar commented Apr 17, 2017

nvkelso commented Apr 17, 2017

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bcamper commented Jun 20, 2017

bcamper commented Oct 2, 2017

meetar commented Oct 19, 2017

bcamper commented Oct 19, 2017