54 lines
1.9 KiB
GLSL
54 lines
1.9 KiB
GLSL
// floor(127 / 2) == 63.0
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// the maximum allowed miter limit is 2.0 at the moment. the extrude normal is
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// stored in a byte (-128..127). we scale regular normals up to length 63, but
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// there are also "special" normals that have a bigger length (of up to 126 in
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// this case).
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#define scale 63.0
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attribute vec2 a_pos;
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attribute vec2 a_extrude;
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attribute float a_linesofar;
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// posmatrix is for the vertex position, exmatrix is for rotating and projecting
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// the extrusion vector.
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uniform mat4 u_matrix;
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uniform mat4 u_exmatrix;
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// shared
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uniform float u_ratio;
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uniform vec2 u_linewidth;
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uniform vec4 u_color;
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varying vec2 v_normal;
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varying float v_linesofar;
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void main() {
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// We store the texture normals in the most insignificant bit
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// transform y so that 0 => -1 and 1 => 1
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// In the texture normal, x is 0 if the normal points straight up/down and 1 if it's a round cap
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// y is 1 if the normal points up, and -1 if it points down
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vec2 normal = mod(a_pos, 2.0);
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normal.y = sign(normal.y - 0.5);
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v_normal = normal;
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// Scale the extrusion vector down to a normal and then up by the line width
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// of this vertex.
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vec2 extrude = a_extrude / scale;
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vec4 dist = vec4(u_linewidth.s * extrude, 0.0, 0.0);
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// If the x coordinate is the maximum integer, we move the z coordinates out
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// of the view plane so that the triangle gets clipped. This makes it easier
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// for us to create degenerate triangle strips.
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float z = step(32767.0, a_pos.x);
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z += step(1.0, v_normal.y);
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// Remove the texture normal bit of the position before scaling it with the
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// model/view matrix. Add the extrusion vector *after* the model/view matrix
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// because we're extruding the line in pixel space, regardless of the current
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// tile's zoom level.
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gl_Position = u_matrix * vec4(floor(a_pos / 2.0), 0.0, 1.0) + u_exmatrix * dist;
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v_linesofar = a_linesofar; // * u_ratio;
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}
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