5.5 KiB
5.5 KiB
id | title | challengeType |
---|---|---|
5a23c84252665b21eecc8045 | Sutherland-Hodgman polygon clipping | 5 |
Description
Instructions
Tests
tests:
- text: <code>clip</code> should be a function.
testString: assert(typeof clip == 'function', '<code>clip</code> should be a function.');
- text: <code>clip([[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]], [[100, 100], [300, 100], [300, 300], [100, 300]])</code> should return a array.
testString: assert(Array.isArray(clip([[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]], [[100, 100], [300, 100], [300, 300], [100, 300]])), '<code>clip([[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]], [[100, 100], [300, 100], [300, 300], [100, 300]])</code> should return a array.');
- text: <code>clip([[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]], [[100, 100], [300, 100], [300, 300], [100, 300]])</code> should return <code>[[100, 116.667], [125, 100], [275, 100], [300, 116.667], [300, 300], [250, 300], [200, 250], [175, 300], [125, 300], [100, 250]]</code>.
testString: assert.deepEqual(clip([[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]], [[100, 100], [300, 100], [300, 300], [100, 300]]), [[100, 116.667], [125, 100], [275, 100], [300, 116.667], [300, 300], [250, 300], [200, 250], [175, 300], [125, 300], [100, 250]], '<code>clip([[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]], [[100, 100], [300, 100], [300, 300], [100, 300]])</code> should return <code>[[100, 116.667], [125, 100], [275, 100], [300, 116.667], [300, 300], [250, 300], [200, 250], [175, 300], [125, 300], [100, 250]]</code>.');
- text: <code>clip([[150, 200], [400, 450], [30, 50]], [[10, 10], [300, 200], [400, 600], [100, 300]])</code> should return <code>[[150, 200], [350, 400], [348.611, 394.444], [30, 50]]</code>.
testString: assert.deepEqual(clip([[150, 200], [400, 450], [30, 50]], [[10, 10], [300, 200], [400, 600], [100, 300]]), [[150, 200], [350, 400], [348.611, 394.444], [30, 50]], '<code>clip([[150, 200], [400, 450], [30, 50]], [[10, 10], [300, 200], [400, 600], [100, 300]])</code> should return <code>[[150, 200], [350, 400], [348.611, 394.444], [30, 50]]</code>.');
- text: <code>clip([[250, 200], [100, 450], [130, 250]], [[50, 60], [100, 230], [400, 600], [100, 300]])</code> should return <code>[[129.167, 329.167], [119.565, 319.565], [121.854, 304.305]]</code>.
testString: assert.deepEqual(clip([[250, 200], [100, 450], [130, 250]], [[50, 60], [100, 230], [400, 600], [100, 300]]), [[129.167, 329.167], [119.565, 319.565], [121.854, 304.305]], '<code>clip([[250, 200], [100, 450], [130, 250]], [[50, 60], [100, 230], [400, 600], [100, 300]])</code> should return <code>[[129.167, 329.167], [119.565, 319.565], [121.854, 304.305]]</code>.');
Challenge Seed
function clip (subjectPolygon, clipPolygon) {
// Good luck!
}
Solution
function clip (subjectPolygon, clipPolygon) {
var cp1, cp2, s, e, i, j;
var inside = function(p) {
return (cp2[0] - cp1[0]) * (p[1] - cp1[1]) > (cp2[1] - cp1[1]) * (p[0] - cp1[0]);
};
var intersection = function() {
var dc = [cp1[0] - cp2[0], cp1[1] - cp2[1]],
dp = [s[0] - e[0], s[1] - e[1]],
n1 = cp1[0] * cp2[1] - cp1[1] * cp2[0],
n2 = s[0] * e[1] - s[1] * e[0],
n3 = 1.0 / (dc[0] * dp[1] - dc[1] * dp[0]);
return [(n1 * dp[0] - n2 * dc[0]) * n3, (n1 * dp[1] - n2 * dc[1]) * n3];
};
var outputList = subjectPolygon;
cp1 = clipPolygon[clipPolygon.length - 1];
for (j in clipPolygon) {
var cp2 = clipPolygon[j];
var inputList = outputList;
outputList = [];
s = inputList[inputList.length - 1]; //last on the input list
for (i in inputList) {
var e = inputList[i];
if (inside(e)) {
if (!inside(s)) {
outputList.push(intersection());
}
outputList.push(e);
} else if (inside(s)) {
outputList.push(intersection());
}
s = e;
}
cp1 = cp2;
}
return outputList.map(e => e.map(f => Math.round(f * 1000) / 1000));
}