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// 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;
}
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