findInverse method Null safety
- double x
Returns the parameter t
that corresponds to the given x value of the spline.
This will only work properly for curves which are single-valued in x
(where every value of x
maps to only one value in 'y', i.e. the curve
does not loop or curve back over itself). For curves that are not
single-valued, it will return the parameter for only one of the values at
the given x
location.
Implementation
double findInverse(double x) {
assert(x != null);
double start = 0.0;
double end = 1.0;
late double mid;
double offsetToOrigin(double pos) => x - transform(pos).dx;
// Use a binary search to find the inverse point within 1e-6, or 100
// subdivisions, whichever comes first.
const double errorLimit = 1e-6;
int count = 100;
final double startValue = offsetToOrigin(start);
while ((end - start) / 2.0 > errorLimit && count > 0) {
mid = (end + start) / 2.0;
final double value = offsetToOrigin(mid);
if (value.sign == startValue.sign) {
start = mid;
} else {
end = mid;
}
count--;
}
return mid;
}