Simplify the minimum sample distance check.

Rather than compute the distance from the start to the new middle, use the
already computed distance from the start to the end. Also, we no longer need the
additional check that the middle is close to either the start or the end because
this is covered by the minimum sample distance check.

d3.js

@@ -3367,8 +3367,8 @@ d3 = function() {
     function resampleLineTo(x0, y0, λ0, a0, b0, c0, x1, y1, λ1, a1, b1, c1, depth, buffer) {
       var dx = x1 - x0, dy = y1 - y0, d2 = dx * dx + dy * dy;
       if (d2 > 4 * δ2 && depth--) {
-        var a = a0 + a1, b = b0 + b1, c = c0 + c1, m = Math.sqrt(a * a + b * b + c * c), φ2 = Math.asin(c /= m), λ2 = Math.abs(Math.abs(c) - 1) < ε ? (λ0 + λ1) / 2 : Math.atan2(b, a), p = project(λ2, φ2), x2 = p[0], y2 = p[1], dx2 = x2 - x0, dy2 = y2 - y0, dz = dy * dx2 - dx * dy2, tooFar = false;
-        if (dz * dz / d2 > δ2 || Math.abs((dx * dx2 + dy * dy2) / d2 - .5) > .3 || (tooFar = dx2 * dx2 + dy2 * dy2 > 256 * δ2)) {
+        var a = a0 + a1, b = b0 + b1, c = c0 + c1, m = Math.sqrt(a * a + b * b + c * c), φ2 = Math.asin(c /= m), λ2 = Math.abs(Math.abs(c) - 1) < ε ? (λ0 + λ1) / 2 : Math.atan2(b, a), p = project(λ2, φ2), x2 = p[0], y2 = p[1], dx2 = x2 - x0, dy2 = y2 - y0, dz = dy * dx2 - dx * dy2, tooFar;
+        if (dz * dz / d2 > δ2 || (tooFar = d2 > 512 * δ2)) {
           var s0 = resampleLineTo(x0, y0, λ0, a0, b0, c0, x2, y2, λ2, a /= m, b /= m, c, depth, buffer);
           buffer.push(p);
           var s1 = resampleLineTo(x2, y2, λ2, a, b, c, x1, y1, λ1, a1, b1, c1, depth, buffer);