void testCosineDistribution()
{
Plot2D plot_radial_hist( output_path + "/cosine_radial_hist.png", plot_size, plot_size );
Plot2D plot_angle_hist( output_path + "/cosine_angle_hist.png", plot_size, plot_size, -0.5f * M_PI, 0.5f * M_PI );
float x = 0.0f, y = 0.0f, z = 0.0f;
// Build a histogram of random angles using a cosine distribution
const int bins = 30;
const float angle_range = 0.5f * M_PI;
const float bin_width = angle_range / bins;
int hist[bins] = {};
for( auto i = 0; i < 1000000; i++ ) {
float angle = rng.cosineQuarterWave();
x = cosf( angle );
y = sinf( angle );
int bin = angle / angle_range * (bins - 1);
hist[bin]++;
}
int *max_it = std::max_element( hist, hist + bins );
int hist_max = *max_it;
plot_radial_hist.drawAxes();
plot_angle_hist.drawAxes();
// Draw histogram bins
plot_radial_hist.strokeColor( 1.0, 0.0, 0.0 );
plot_angle_hist.strokeColor( 1.0, 0.0, 0.0 );
for( auto i = 0; i < bins; i++ ) {
float angle = (float) i / (bins - 1) * angle_range;
float r = hist[i] / (float) hist_max;
float x1 = cosf( angle ) * r;
float y1 = sinf( angle ) * r;
angle = (float) (i + 1) / (bins - 1) * angle_range;
float x2 = cosf( angle ) * r;
float y2 = sinf( angle ) * r;
plot_radial_hist.drawLine( x1, y1, 0.0, 0.0 );
plot_radial_hist.drawLine( x1, y1, x2, y2 );
plot_radial_hist.drawLine( 0.0, 0.0, x2, y2 );
plot_angle_hist.drawLine( angle, 0.0, angle, r );
plot_angle_hist.drawLine( angle, r, angle + bin_width, r );
plot_angle_hist.drawLine( angle + bin_width, r, angle + bin_width, 0.0 );
}
// Reference
plot_angle_hist.strokeColor( 1.0, 0.0, 0.0 );
for( auto i = 0; i < 100; i++ ) {
float angle1 = (float) i / (bins - 1) * angle_range;
float angle2 = (float) (i + 1) / (bins - 1) * angle_range;
float r1 = cos(angle1);
float r2 = cos(angle2);
plot_angle_hist.drawLine( angle1, r1, angle2, r2 );
}
}
