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); } }