1 files changed, 45 insertions, 0 deletions
diff --git a/src/mbgl/shader/line.vertex.glsl b/src/mbgl/shader/line.vertex.glsl
new file mode 100644
index 0000000000..1d8e687c95
--- /dev/null
+++ b/src/mbgl/shader/line.vertex.glsl
@@ -0,0 +1,45 @@
+// floor(127 / 2) == 63.0
+// the maximum allowed miter limit is 2.0 at the moment. the extrude normal is
+// stored in a byte (-128..127). we scale regular normals up to length 63, but
+// there are also "special" normals that have a bigger length (of up to 126 in
+// this case).
+// #define scale 63.0
+#define scale 0.015873016
+
+attribute vec2 a_pos;
+attribute vec2 a_extrude;
+attribute float a_linesofar;
+
+// matrix is for the vertex position, exmatrix is for rotating and projecting
+// the extrusion vector.
+uniform mat4 u_matrix;
+uniform mat4 u_exmatrix;
+
+// shared
+uniform float u_ratio;
+uniform vec2 u_linewidth;
+uniform vec4 u_color;
+
+varying vec2 v_normal;
+varying float v_linesofar;
+
+void main() {
+    // We store the texture normals in the most insignificant bit
+    // transform y 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
+    vec2 normal = mod(a_pos, 2.0);
+    normal.y = sign(normal.y - 0.5);
+    v_normal = normal;
+
+    // Scale the extrusion vector down to a normal and then up by the line width
+    // of this vertex.
+    vec4 dist = vec4(u_linewidth.s * a_extrude * scale, 0.0, 0.0);
+
+    // Remove the texture normal bit of the position before scaling it with the
+    // model/view matrix. Add the extrusion vector *after* the model/view matrix
+    // because we're extruding the line in pixel space, regardless of the current
+    // tile's zoom level.
+    gl_Position = u_matrix * vec4(floor(a_pos * 0.5), 0.0, 1.0) + u_exmatrix * dist;
+    v_linesofar = a_linesofar * u_ratio;
+}