// TODO: implement adaptive supersampling
RGBColour World::colourForPixelAt(int i, int j) {
double d = viewport.getViewingDistance();
if (ss_level == 1) {
// no super-sampling
double uValue = viewport.uAmount(i, 1, 0, false);
double vValue = viewport.vAmount(j, 1, 0, false);
vec3 direction = wAxis.scaled(-d) + uAxis.scaled(uValue) + vAxis.scaled(vValue);
Ray theRay(cameraPosition, direction);
return RGBColour(traceRay(theRay, 0.0, 0));
}
// 0.01 => x16, 1.2 => x64
double thresholds[2] = {0.01, 1.2};
double var = 0.0;
int lvl_log = 2;
RGBVec pixelColour;
while (lvl_log <= ss_level) {
pixelColour = RGBVec(0.0,0.0,0.0);
int lvl = int_pow(2, lvl_log - 1);
double scale_factor = 1.0 / static_cast<double>(lvl*lvl);
vec3 sum_x_sq(0.0,0.0,0.0);
for (int a = 0; a < lvl; a++) {
for (int b = 0; b < lvl; b++) {
double uValue = viewport.uAmount(i, ss_level, a, lvl_log > 2);
double vValue = viewport.vAmount(j, ss_level, b, lvl_log > 2);
vec3 direction = wAxis.scaled(-d) + uAxis.scaled(uValue) + vAxis.scaled(vValue);
Ray theRay(cameraPosition, direction);
RGBVec sample = traceRay(theRay, 0.0, 0).scaled(scale_factor);
pixelColour += sample;
if (ss_level > 2) sum_x_sq += sample.getVector().pointwise(sample.getVector());
}
}
if (lvl_log == 2 && ss_level > 2) {
vec3 varvec = sum_x_sq.scaled(scale_factor) - pixelColour.getVector().pointwise(pixelColour.getVector());
var = varvec.magnitude();
if (i % 100 == 0 && j % 100 == 0) std::cout << "var: " << var << std::endl;
}
if (var < thresholds[lvl_log - 2] || lvl_log == ss_level) break;
lvl_log++;
}
if (lvl_log == 2) renderStats.ss_x4++;
else if (lvl_log == 3) renderStats.ss_x16++;
else if (lvl_log == 4) renderStats.ss_x64++;
return RGBColour(pixelColour);
}
Ray ray_for_pixel (int x_, int y_) const {
float delta_x = float((x_ + 0.5f) - m_x_res * 0.5f) / (m_x_res * 0.5f);
float delta_y = float((y_ + 0.5f) - m_y_res * 0.5f) / (m_y_res * 0.5f);
// initialize ray diffferentials
Vector3D d = m_z + (m_x * delta_x) + (m_y * delta_y);
Vector3D dPdx, dPdy, dDdx, dDdy;
dDdx = (( (m_x * d.dot(d)) - (d * d.dot(m_x)) )*(1.f/std::pow(d.dot(d), 1.5))) * (1.f/((float)m_x_res*0.5f));
dDdy = (( (m_y * d.dot(d)) - (d * d.dot(m_y)) )*(1.f/std::pow(d.dot(d), 1.5))) * (1.f/((float)m_y_res*0.5f));
Ray theRay(m_pos, d.normalize());
theRay.setdDdx(dDdx);
theRay.setdDdy(dDdy);
theRay.setdPdx(dPdx);
theRay.setdPdy(dPdy);
return theRay;
}
