[core] Use separate attribute component for line normals

include/mbgl/util/constants.hpp

@@ -19,7 +19,8 @@ constexpr float tileSize = 512;
  *
  * Positions are stored as signed 16bit integers.
  * One bit is lost for signedness to support features extending past the left edge of the tile.
- * One bit is lost because the line vertex buffer packs 1 bit of other data into the int.
+ * 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/mbgl/programs/attributes.hpp

@@ -23,6 +23,7 @@ inline uint16_t packUint8Pair(T a, T b) {
 MBGL_DEFINE_ATTRIBUTE(int16_t, 2, a_pos);
 MBGL_DEFINE_ATTRIBUTE(int16_t, 2, a_extrude);
 MBGL_DEFINE_ATTRIBUTE(int16_t, 4, a_pos_offset);
+MBGL_DEFINE_ATTRIBUTE(int16_t, 3, a_pos_normal);
 MBGL_DEFINE_ATTRIBUTE(uint16_t, 2, a_texture_pos);
 MBGL_DEFINE_ATTRIBUTE(int16_t,  3, a_normal);
 MBGL_DEFINE_ATTRIBUTE(uint16_t, 1, a_edgedistance);

src/mbgl/programs/line_program.cpp

@@ -10,7 +10,7 @@ namespace mbgl {
 
 using namespace style;
 
-static_assert(sizeof(LineLayoutVertex) == 8, "expected LineLayoutVertex size");
+static_assert(sizeof(LineLayoutVertex) == 10, "expected LineLayoutVertex size");
 
 template <class Values, class...Args>
 Values makeValues(const LinePaintProperties::Evaluated& properties,

src/mbgl/programs/line_program.hpp

@@ -31,7 +31,7 @@ MBGL_DEFINE_UNIFORM_VECTOR(float, 2, u_gl_units_to_pixels);
 } // namespace uniforms
 
 struct LineLayoutAttributes : gl::Attributes<
-    attributes::a_pos,
+    attributes::a_pos_normal,
     attributes::a_data<uint8_t, 4>>
 {};
 
@@ -52,14 +52,16 @@ class LineProgram : public Program<
     /*
      * @param p vertex position
      * @param e extrude normal
-     * @param t texture normal
+     * @param round whether the vertex uses a round line cap
+     * @param up whether the line normal points up or down
      * @param dir direction of the line cap (-1/0/1)
      */
-    static LayoutVertex layoutVertex(Point<int16_t> p, Point<double> e, Point<bool> t, int8_t dir, int32_t linesofar = 0) {
+    static LayoutVertex layoutVertex(Point<int16_t> p, Point<double> e, bool round, bool up, int8_t dir, int32_t linesofar = 0) {
         return LayoutVertex {
             {{
-                static_cast<int16_t>((p.x * 2) | t.x),
-                static_cast<int16_t>((p.y * 2) | t.y)
+                p.x,
+                p.y,
+                static_cast<int16_t>(attributes::packUint8Pair(round ? 1 : 0, up ? 1 : 0))
             }},
             {{
                 // add 128 to store a byte in an unsigned byte

src/mbgl/renderer/line_bucket.cpp

@@ -398,7 +398,7 @@ void LineBucket::addCurrentVertex(const GeometryCoordinate& currentCoordinate,
     Point<double> extrude = normal;
     if (endLeft)
         extrude = extrude - (util::perp(normal) * endLeft);
-    vertices.emplace_back(LineProgram::layoutVertex(currentCoordinate, extrude, { round, false }, endLeft, distance * LINE_DISTANCE_SCALE));
+    vertices.emplace_back(LineProgram::layoutVertex(currentCoordinate, extrude, round, false, endLeft, distance * LINE_DISTANCE_SCALE));
     e3 = vertices.vertexSize() - 1 - startVertex;
     if (e1 >= 0 && e2 >= 0) {
         triangleStore.emplace_back(e1, e2, e3);
@@ -409,7 +409,7 @@ void LineBucket::addCurrentVertex(const GeometryCoordinate& currentCoordinate,
     extrude = normal * -1.0;
     if (endRight)
         extrude = extrude - (util::perp(normal) * endRight);
-    vertices.emplace_back(LineProgram::layoutVertex(currentCoordinate, extrude, { round, true }, -endRight, distance * LINE_DISTANCE_SCALE));
+    vertices.emplace_back(LineProgram::layoutVertex(currentCoordinate, extrude, round, true, -endRight, distance * LINE_DISTANCE_SCALE));
     e3 = vertices.vertexSize() - 1 - startVertex;
     if (e1 >= 0 && e2 >= 0) {
         triangleStore.emplace_back(e1, e2, e3);
@@ -434,7 +434,7 @@ void LineBucket::addPieSliceVertex(const GeometryCoordinate& currentVertex,
                                    std::size_t startVertex,
                                    std::vector<TriangleElement>& triangleStore) {
     Point<double> flippedExtrude = extrude * (lineTurnsLeft ? -1.0 : 1.0);
-    vertices.emplace_back(LineProgram::layoutVertex(currentVertex, flippedExtrude, { false, lineTurnsLeft }, 0, distance * LINE_DISTANCE_SCALE));
+    vertices.emplace_back(LineProgram::layoutVertex(currentVertex, flippedExtrude, false, lineTurnsLeft, 0, distance * LINE_DISTANCE_SCALE));
     e3 = vertices.vertexSize() - 1 - startVertex;
     if (e1 >= 0 && e2 >= 0) {
         triangleStore.emplace_back(e1, e2, e3);

src/mbgl/shaders/line.cpp

@@ -21,7 +21,7 @@ const char* line::vertexSource = R"MBGL_SHADER(
 // #define scale 63.0
 #define scale 0.015873016
 
-attribute vec2 a_pos;
+attribute vec3 a_pos_normal;
 attribute vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -107,20 +107,21 @@ void main() {
     vec2 a_extrude = a_data.xy - 128.0;
     float a_direction = mod(a_data.z, 4.0) - 1.0;
 
-    // We store the texture normals in the most insignificant bit
-    // transform y so that 0 => -1 and 1 => 1
+    vec2 pos = a_pos_normal.xy;
+
+    // transform y normal so that 0 => -1 and 1 => 1
     // In the texture normal, x is 0 if the normal points straight up/down and 1 if it's a round cap
     // y is 1 if the normal points up, and -1 if it points down
-    mediump vec2 normal = mod(a_pos, 2.0);
+    mediump vec2 normal = unpack_float(a_pos_normal.z);
     normal.y = sign(normal.y - 0.5);
-    v_normal = normal;
 
+    v_normal = normal;
 
-    // these transformations used to be applied in the JS and native code bases. 
-    // moved them into the shader for clarity and simplicity. 
+    // these transformations used to be applied in the JS and native code bases.
+    // moved them into the shader for clarity and simplicity.
     gapwidth = gapwidth / 2.0;
     float width = u_width / 2.0;
-    offset = -1.0 * offset; 
+    offset = -1.0 * offset;
 
     float inset = gapwidth + (gapwidth > 0.0 ? ANTIALIASING : 0.0);
     float outset = gapwidth + width * (gapwidth > 0.0 ? 2.0 : 1.0) + ANTIALIASING;
@@ -137,9 +138,6 @@ void main() {
     mediump float t = 1.0 - abs(u);
     mediump vec2 offset2 = offset * a_extrude * scale * normal.y * mat2(t, -u, u, t);
 
-    // Remove the texture normal bit to get the position
-    vec2 pos = floor(a_pos * 0.5);
-
     vec4 projected_extrude = u_matrix * vec4(dist / u_ratio, 0.0, 0.0);
     gl_Position = u_matrix * vec4(pos + offset2 / u_ratio, 0.0, 1.0) + projected_extrude;
 

src/mbgl/shaders/line_pattern.cpp

@@ -23,7 +23,7 @@ const char* line_pattern::vertexSource = R"MBGL_SHADER(
 // Retina devices need a smaller distance to avoid aliasing.
 #define ANTIALIASING 1.0 / DEVICE_PIXEL_RATIO / 2.0
 
-attribute vec2 a_pos;
+attribute vec3 a_pos_normal;
 attribute vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -97,19 +97,21 @@ 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;
 
-    // We store the texture normals in the most insignificant bit
-    // transform y so that 0 => -1 and 1 => 1
+    vec2 pos = a_pos_normal.xy;
+
+    // transform y normal so that 0 => -1 and 1 => 1
     // In the texture normal, x is 0 if the normal points straight up/down and 1 if it's a round cap
     // y is 1 if the normal points up, and -1 if it points down
-    mediump vec2 normal = mod(a_pos, 2.0);
+    mediump vec2 normal = unpack_float(a_pos_normal.z);
     normal.y = sign(normal.y - 0.5);
+
     v_normal = normal;
 
-    // these transformations used to be applied in the JS and native code bases. 
-    // moved them into the shader for clarity and simplicity. 
+    // these transformations used to be applied in the JS and native code bases.
+    // moved them into the shader for clarity and simplicity.
     gapwidth = gapwidth / 2.0;
     float width = u_width / 2.0;
-    offset = -1.0 * offset; 
+    offset = -1.0 * offset;
 
     float inset = gapwidth + (gapwidth > 0.0 ? ANTIALIASING : 0.0);
     float outset = gapwidth + width * (gapwidth > 0.0 ? 2.0 : 1.0) + ANTIALIASING;
@@ -126,9 +128,6 @@ void main() {
     mediump float t = 1.0 - abs(u);
     mediump vec2 offset2 = offset * a_extrude * scale * normal.y * mat2(t, -u, u, t);
 
-    // Remove the texture normal bit to get the position
-    vec2 pos = floor(a_pos * 0.5);
-
     vec4 projected_extrude = u_matrix * vec4(dist / u_ratio, 0.0, 0.0);
     gl_Position = u_matrix * vec4(pos + offset2 / u_ratio, 0.0, 1.0) + projected_extrude;
 

src/mbgl/shaders/line_sdf.cpp

@@ -23,7 +23,7 @@ const char* line_sdf::vertexSource = R"MBGL_SHADER(
 // Retina devices need a smaller distance to avoid aliasing.
 #define ANTIALIASING 1.0 / DEVICE_PIXEL_RATIO / 2.0
 
-attribute vec2 a_pos;
+attribute vec3 a_pos_normal;
 attribute vec4 a_data;
 
 uniform mat4 u_matrix;
@@ -116,20 +116,22 @@ 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;
 
-    // We store the texture normals in the most insignificant bit
-    // transform y so that 0 => -1 and 1 => 1
+    vec2 pos = a_pos_normal.xy;
+
+    // transform y normal so that 0 => -1 and 1 => 1
     // In the texture normal, x is 0 if the normal points straight up/down and 1 if it's a round cap
     // y is 1 if the normal points up, and -1 if it points down
-    mediump vec2 normal = mod(a_pos, 2.0);
+    mediump vec2 normal = unpack_float(a_pos_normal.z);
     normal.y = sign(normal.y - 0.5);
+
     v_normal = normal;
 
-    // these transformations used to be applied in the JS and native code bases. 
-    // moved them into the shader for clarity and simplicity. 
+    // these transformations used to be applied in the JS and native code bases.
+    // moved them into the shader for clarity and simplicity.
     gapwidth = gapwidth / 2.0;
     float width = u_width / 2.0;
     offset = -1.0 * offset;
- 
+
     float inset = gapwidth + (gapwidth > 0.0 ? ANTIALIASING : 0.0);
     float outset = gapwidth + width * (gapwidth > 0.0 ? 2.0 : 1.0) + ANTIALIASING;
 
@@ -145,9 +147,6 @@ void main() {
     mediump float t = 1.0 - abs(u);
     mediump vec2 offset2 = offset * a_extrude * scale * normal.y * mat2(t, -u, u, t);
 
-    // Remove the texture normal bit to get the position
-    vec2 pos = floor(a_pos * 0.5);
-
     vec4 projected_extrude = u_matrix * vec4(dist / u_ratio, 0.0, 0.0);
     gl_Position = u_matrix * vec4(pos + offset2 / u_ratio, 0.0, 1.0) + projected_extrude;