don't use bit in coordinates for up and round attributes

this effectively reverts mapbox/mapbox-gl-js#8306

src/data/bucket/line_attributes.ts

@@ -1,7 +1,7 @@
 import {createLayout} from '../../util/struct_array';
 
 const lineLayoutAttributes = createLayout([
-    {name: 'a_pos_normal', components: 2, type: 'Int16'},
+    {name: 'a_pos_normal', components: 4, type: 'Int16'},
     {name: 'a_data', components: 4, type: 'Uint8'}
 ], 4);
 

src/data/bucket/line_bucket.ts

@@ -540,8 +540,10 @@ class LineBucket implements Bucket {
         this.layoutVertexArray.emplaceBack(
             // a_pos_normal
             // Encode round/up the least significant bits
-            (x << 1) + (round ? 1 : 0),
-            (y << 1) + (up ? 1 : 0),
+            x,
+            y,
+            round ? 1 : 0,
+            up ? 1 : -1,
             // a_data
             // add 128 to store a byte in an unsigned byte
             Math.round(EXTRUDE_SCALE * extrudeX) + 128,

src/shaders/line.vertex.glsl

@@ -6,7 +6,7 @@
 // #define scale 63.0
 #define scale 0.015873016
 
-in vec2 a_pos_normal;
+in vec4 a_pos_normal;
 in vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -43,13 +43,11 @@ void main() {
 
     v_linesofar = (floor(a_data.z / 4.0) + a_data.w * 64.0) * 2.0;
 
-    vec2 pos = floor(a_pos_normal * 0.5);
+    vec2 pos = a_pos_normal.xy;
 
     // 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
-    // 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;
+    mediump vec2 normal = a_pos_normal.zw;
     v_normal = normal;
 
     // these transformations used to be applied in the JS and native code bases.

src/shaders/line_gradient.vertex.glsl

@@ -6,7 +6,7 @@
 // #define scale 63.0
 #define scale 0.015873016
 
-in vec2 a_pos_normal;
+in vec4 a_pos_normal;
 in vec4 a_data;
 in float a_uv_x;
 in float a_split_index;
@@ -46,13 +46,11 @@ void main() {
     highp float half_texel_height = 0.5 * texel_height;
     v_uv = vec2(a_uv_x, a_split_index * texel_height - half_texel_height);
 
-    vec2 pos = floor(a_pos_normal * 0.5);
+    vec2 pos = a_pos_normal.xy;
 
     // 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
-    // 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;
+    mediump vec2 normal = a_pos_normal.zw;
     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
 
-in vec2 a_pos_normal;
+in vec4 a_pos_normal;
 in vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -55,13 +55,11 @@ 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.x;
-    vec2 pos = floor(a_pos_normal * 0.5);
+    vec2 pos = a_pos_normal.xy;
 
     // 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
-    // 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;
+    mediump vec2 normal = a_pos_normal.zw;
     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
 
-in vec2 a_pos_normal;
+in vec4 a_pos_normal;
 in vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -53,13 +53,11 @@ 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 = floor(a_pos_normal * 0.5);
+    vec2 pos = a_pos_normal.xy;
 
     // 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
-    // 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;
+    mediump vec2 normal = a_pos_normal.zw;
     v_normal = normal;
 
     // these transformations used to be applied in the JS and native code bases.