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Minor cleanup and optimization of Sketch #24964

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Merged
merged 1 commit into from
Feb 2, 2023
Merged

Minor cleanup and optimization of Sketch #24964

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28 changes: 23 additions & 5 deletions src/path_converters.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1018,6 +1018,9 @@ class Sketch
m_rand(0)
{
rewind(0);
const double d_M_PI = 3.14159265358979323846;
m_p_scale = (2.0 * d_M_PI) / (m_length * m_randomness);
m_log_randomness = 2.0 * log(m_randomness);
}

unsigned vertex(double *x, double *y)
Expand All @@ -1037,18 +1040,31 @@ class Sketch
// We want the "cursor" along the sine wave to move at a
// random rate.
double d_rand = m_rand.get_double();
double d_M_PI = 3.14159265358979323846;
m_p += pow(m_randomness, d_rand * 2.0 - 1.0);
double r = sin(m_p / (m_length / (d_M_PI * 2.0))) * m_scale;
// Original computation
// p += pow(k, 2*rand - 1)
// r = sin(p * c)
// x86 computes pow(a, b) as exp(b*log(a))
// First, move -1 out, so
// p' += pow(k, 2*rand)
// r = sin(p * c') where c' = c / k
// Next, use x86 logic (will not be worse on other platforms as
// the log is only computed once and pow and exp are, at worst,
// the same)
// So p+= exp(2*rand*log(k))
// lk = 2*log(k)
// p += exp(rand*lk)
m_p += exp(d_rand * m_log_randomness);
double den = m_last_x - *x;
double num = m_last_y - *y;
double len = num * num + den * den;
m_last_x = *x;
m_last_y = *y;
if (len != 0) {
len = sqrt(len);
*x += r * num / len;
*y += r * -den / len;
double r = sin(m_p * m_p_scale) * m_scale;
double roverlen = r / len;
*x += roverlen * num;
*y -= roverlen * den;
}
} else {
m_last_x = *x;
Expand Down Expand Up @@ -1083,6 +1099,8 @@ class Sketch
bool m_has_last;
double m_p;
RandomNumberGenerator m_rand;
double m_p_scale;
double m_log_randomness;
};

#endif // MPL_PATH_CONVERTERS_H