Switch back to a more compact line attributes layout

src/data/array_types.js

@@ -115,12 +115,12 @@ register('StructArrayLayout2i4i12', StructArrayLayout2i4i12);
 
 /**
  * Implementation of the StructArray layout:
- * [0]: Int16[4]
- * [8]: Uint8[4]
+ * [0]: Int16[2]
+ * [4]: Uint8[4]
  *
  * @private
  */
-class StructArrayLayout4i4ub12 extends StructArray {
+class StructArrayLayout2i4ub8 extends StructArray {
     uint8: Uint8Array;
     int16: Int16Array;
 
@@ -129,29 +129,27 @@ class StructArrayLayout4i4ub12 extends StructArray {
         this.int16 = new Int16Array(this.arrayBuffer);
     }
 
-    emplaceBack(v0: number, v1: number, v2: number, v3: number, v4: number, v5: number, v6: number, v7: number) {
+    emplaceBack(v0: number, v1: number, v2: number, v3: number, v4: number, v5: number) {
         const i = this.length;
         this.resize(i + 1);
-        return this.emplace(i, v0, v1, v2, v3, v4, v5, v6, v7);
+        return this.emplace(i, v0, v1, v2, v3, v4, v5);
     }
 
-    emplace(i: number, v0: number, v1: number, v2: number, v3: number, v4: number, v5: number, v6: number, v7: number) {
-        const o2 = i * 6;
-        const o1 = i * 12;
+    emplace(i: number, v0: number, v1: number, v2: number, v3: number, v4: number, v5: number) {
+        const o2 = i * 4;
+        const o1 = i * 8;
         this.int16[o2 + 0] = v0;
         this.int16[o2 + 1] = v1;
-        this.int16[o2 + 2] = v2;
-        this.int16[o2 + 3] = v3;
-        this.uint8[o1 + 8] = v4;
-        this.uint8[o1 + 9] = v5;
-        this.uint8[o1 + 10] = v6;
-        this.uint8[o1 + 11] = v7;
+        this.uint8[o1 + 4] = v2;
+        this.uint8[o1 + 5] = v3;
+        this.uint8[o1 + 6] = v4;
+        this.uint8[o1 + 7] = v5;
         return i;
     }
 }
 
-StructArrayLayout4i4ub12.prototype.bytesPerElement = 12;
-register('StructArrayLayout4i4ub12', StructArrayLayout4i4ub12);
+StructArrayLayout2i4ub8.prototype.bytesPerElement = 8;
+register('StructArrayLayout2i4ub8', StructArrayLayout2i4ub8);
 
 
 /**
@@ -1131,7 +1129,7 @@ export {
     StructArrayLayout2i4,
     StructArrayLayout4i8,
     StructArrayLayout2i4i12,
-    StructArrayLayout4i4ub12,
+    StructArrayLayout2i4ub8,
     StructArrayLayout8ui16,
     StructArrayLayout4i4ui16,
     StructArrayLayout3f12,
@@ -1155,7 +1153,7 @@ export {
     StructArrayLayout2i4 as FillLayoutArray,
     StructArrayLayout2i4i12 as FillExtrusionLayoutArray,
     StructArrayLayout2i4 as HeatmapLayoutArray,
-    StructArrayLayout4i4ub12 as LineLayoutArray,
+    StructArrayLayout2i4ub8 as LineLayoutArray,
     StructArrayLayout8ui16 as PatternLayoutArray,
     StructArrayLayout4i4ui16 as SymbolLayoutArray,
     StructArrayLayout3f12 as SymbolDynamicLayoutArray,

src/data/bucket/line_attributes.js

@@ -2,7 +2,7 @@
 import { createLayout } from '../../util/struct_array';
 
 const lineLayoutAttributes = createLayout([
-    {name: 'a_pos_normal', components: 4, type: 'Int16'},
+    {name: 'a_pos_normal', components: 2, type: 'Int16'},
     {name: 'a_data', components: 4, type: 'Uint8'}
 ], 4);
 

src/data/bucket/line_bucket.js

@@ -66,10 +66,9 @@ const MAX_LINE_DISTANCE = Math.pow(2, LINE_DISTANCE_BUFFER_BITS - 1) / LINE_DIST
 function addLineVertex(layoutVertexBuffer, point: Point, extrude: Point, round: boolean, up: boolean, dir: number, linesofar: number) {
     layoutVertexBuffer.emplaceBack(
         // a_pos_normal
-        point.x,
-        point.y,
-        round ? 1 : 0,
-        up ? 1 : -1,
+        // Encode round/up the least significant bits
+        (point.x << 1) + (round ? 1 : 0),
+        (point.y << 1) + (up ? 1 : 0),
         // a_data
         // add 128 to store a byte in an unsigned byte
         Math.round(EXTRUDE_SCALE * extrude.x) + 128,

src/data/extent.js

@@ -9,7 +9,6 @@
  * * Vertex buffer store positions as signed 16 bit integers.
  * * One bit is lost for signedness to support tile buffers.
  * * One bit is lost because the line vertex buffer used to pack 1 bit of other data into the int.
- *   This is no longer the case but we're reserving this bit anyway.
  * * One bit is lost to support features extending past the extent on the right edge of the tile.
  * * This leaves us with 2^13 = 8192
  *

src/shaders/line.vertex.glsl

@@ -6,7 +6,7 @@
 // #define scale 63.0
 #define scale 0.015873016
 
-attribute vec4 a_pos_normal;
+attribute vec2 a_pos_normal;
 attribute vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -43,11 +43,13 @@ void main() {
 
     v_linesofar = (floor(a_data.z / 4.0) + a_data.w * 64.0) * 2.0;
 
-    vec2 pos = a_pos_normal.xy;
+    vec2 pos = floor(a_pos_normal * 0.5);
 
     // x is 1 if it's a round cap, 0 otherwise
     // y is 1 if the normal points up, and -1 if it points down
-    mediump vec2 normal = a_pos_normal.zw;
+    // We store these in the least significant bit of a_pos_normal
+    mediump vec2 normal = a_pos_normal - 2.0 * pos;
+    normal.y = normal.y * 2.0 - 1.0;
     v_normal = normal;
 
     // these transformations used to be applied in the JS and native code bases.

src/shaders/line_gradient.vertex.glsl

@@ -10,7 +10,7 @@
 // #define scale 63.0
 #define scale 0.015873016
 
-attribute vec4 a_pos_normal;
+attribute vec2 a_pos_normal;
 attribute vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -45,11 +45,13 @@ void main() {
 
     v_lineprogress = (floor(a_data.z / 4.0) + a_data.w * 64.0) * 2.0 / MAX_LINE_DISTANCE;
 
-    vec2 pos = a_pos_normal.xy;
+    vec2 pos = floor(a_pos_normal * 0.5);
 
     // x is 1 if it's a round cap, 0 otherwise
     // y is 1 if the normal points up, and -1 if it points down
-    mediump vec2 normal = a_pos_normal.zw;
+    // We store these in the least significant bit of a_pos_normal
+    mediump vec2 normal = a_pos_normal - 2.0 * pos;
+    normal.y = normal.y * 2.0 - 1.0;
     v_normal = normal;
 
     // these transformations used to be applied in the JS and native code bases.

src/shaders/line_pattern.vertex.glsl

@@ -10,7 +10,7 @@
 // long distances for long segments. Use this value to unscale the distance.
 #define LINE_DISTANCE_SCALE 2.0
 
-attribute vec4 a_pos_normal;
+attribute vec2 a_pos_normal;
 attribute vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -48,11 +48,13 @@ void main() {
     float a_direction = mod(a_data.z, 4.0) - 1.0;
     float a_linesofar = (floor(a_data.z / 4.0) + a_data.w * 64.0) * LINE_DISTANCE_SCALE;
     // float tileRatio = u_scale.y;
-    vec2 pos = a_pos_normal.xy;
+    vec2 pos = floor(a_pos_normal * 0.5);
 
     // x is 1 if it's a round cap, 0 otherwise
     // y is 1 if the normal points up, and -1 if it points down
-    mediump vec2 normal = a_pos_normal.zw;
+    // We store these in the least significant bit of a_pos_normal
+    mediump vec2 normal = a_pos_normal - 2.0 * pos;
+    normal.y = normal.y * 2.0 - 1.0;
     v_normal = normal;
 
     // these transformations used to be applied in the JS and native code bases.

src/shaders/line_sdf.vertex.glsl

@@ -10,7 +10,7 @@
 // long distances for long segments. Use this value to unscale the distance.
 #define LINE_DISTANCE_SCALE 2.0
 
-attribute vec4 a_pos_normal;
+attribute vec2 a_pos_normal;
 attribute vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -53,11 +53,13 @@ void main() {
     float a_direction = mod(a_data.z, 4.0) - 1.0;
     float a_linesofar = (floor(a_data.z / 4.0) + a_data.w * 64.0) * LINE_DISTANCE_SCALE;
 
-    vec2 pos = a_pos_normal.xy;
+    vec2 pos = floor(a_pos_normal * 0.5);
 
     // x is 1 if it's a round cap, 0 otherwise
     // y is 1 if the normal points up, and -1 if it points down
-    mediump vec2 normal = a_pos_normal.zw;
+    // We store these in the least significant bit of a_pos_normal
+    mediump vec2 normal = a_pos_normal - 2.0 * pos;
+    normal.y = normal.y * 2.0 - 1.0;
     v_normal = normal;
 
     // these transformations used to be applied in the JS and native code bases.