static double evaluate(const double* dataset, size_t stride, float turbidity, float albedo, float sunTheta)
{
// splines are functions of elevation^1/3
double elevationK = pow(max(0.f, 1 - sunTheta / (glm::pi<float>() / 2)), 1 / 3.0);
// table has values for turbidity 1..10
int turbidity0 = glm::clamp(static_cast<int>(turbidity), 1, 10);
int turbidity1 = min(turbidity0 + 1, 10);
float turbidityK = glm::clamp(turbidity - turbidity0, 0.f, 1.f);
const double* datasetA0 = dataset;
const double* datasetA1 = dataset + stride * 6 * 10;
double a0t0 = evaluateSpline(datasetA0 + stride * 6 * (turbidity0 - 1), stride, elevationK);
double a1t0 = evaluateSpline(datasetA1 + stride * 6 * (turbidity0 - 1), stride, elevationK);
double a0t1 = evaluateSpline(datasetA0 + stride * 6 * (turbidity1 - 1), stride, elevationK);
double a1t1 = evaluateSpline(datasetA1 + stride * 6 * (turbidity1 - 1), stride, elevationK);
return
a0t0 * (1 - albedo) * (1 - turbidityK) +
a1t0 * albedo * (1 - turbidityK) +
a0t1 * (1 - albedo) * turbidityK +
a1t1 * albedo * turbidityK;
}
void Spline::generateArcLengthTable()
{
USING_ATLAS_MATH_NS;
if (!mTable.empty())
{
mTable.clear();
}
float scale = 1.0f / mResolution;
mTable.push_back(0.0f);
for (int i = 1; i < mResolution + 1; ++i)
{
Point p0 = evaluateSpline((i - 1) * scale);
Point p1 = evaluateSpline(i * scale);
Point dist = p0 - p1;
mTable.push_back(mTable[i - 1] + glm::length(dist));
}
}
atlas::math::Point Spline::interpolateOnSpline()
{
int n = int(mTable.size());
float totalDistance = mTable[n - 1];
float step = totalDistance / mTotalFrames;
float currDistance = step * mCurrentFrame;
int index = tableLookUp(currDistance);
float t = (1.0f / mResolution) * (index % mResolution);
return evaluateSpline(t);
}
