private void raytrace(double energyEV, int numRays) {
Grid2D grid = new Grid2D(600, 500);
FloatProcessor imp;
imp = new FloatProcessor(grid.getWidth(), grid.getHeight());
imp.setPixels(grid.getBuffer());
// SimpleVector startPosition = new SimpleVector(40,grid.getHeight()/2/scale, 0);
SimpleVector startPosition = new SimpleVector(0, 0, 0);
for (int i = 0; i < numRays; ++i) {
followRay(startPosition.clone(), new SimpleVector(1, 0, 0), energyEV, imp, 0, 0);
}
imp.drawString(
grid.getWidth() / scale + "cm",
grid.getWidth() / 2 - 20,
grid.getHeight() - 10,
Color.WHITE);
grid.show("Energy: " + energyEV + "eV, Material: " + material.getName());
System.out.println(
"Rejection sampling: average misses per draw: " + (float) sumMisses / (float) numDraws);
numDraws = 0;
sumMisses = 0;
}
private void followRay(
SimpleVector pos,
SimpleVector dir,
double energyEV,
FloatProcessor imp,
int scatterCount,
double totalDistance) {
if (energyEV <= 1 || scatterCount > 20000) {
System.out.println("energy low, times scattered: " + scatterCount);
return;
}
// follow ray until next interaction point
SimpleVector oldPos = pos.clone();
double dist = sampler.getDistanceUntilNextInteractionCm(material, energyEV);
pos.add(dir.multipliedBy(dist));
pathlengths.add(dist);
// draw the entire path
// imp.drawLine((int)(scale*oldPos.getElement(0)), (int)(scale*oldPos.getElement(1)),
// (int)(scale*pos.getElement(0)), (int)(scale*pos.getElement(1)));
// draw interaction points only
imp.drawDot((int) (scale * pos.getElement(0)), (int) (scale * pos.getElement(1)));
// choose compton or photoelectric effect
double photo =
material.getAttenuation(energyEV / 1000, AttenuationType.PHOTOELECTRIC_ABSORPTION);
double compton =
material.getAttenuation(energyEV / 1000, AttenuationType.INCOHERENT_ATTENUATION);
if (sampler.random() * (photo + compton) <= photo) {
// photoelectric absorption
energyEV = 0;
// System.out.println("absorbed after " + scatterCount + " collisions");
xs.add(pos.getElement(0));
ys.add(pos.getElement(1));
zs.add(pos.getElement(2));
return;
} else {
// compton scattering
energyEV = sampler.sampleComptonScattering(energyEV, dir);
// send new ray
followRay(pos, dir, energyEV, imp, scatterCount + 1, totalDistance + dist);
}
}
