@Override
public BoundingBox getBounds() {
// If there are no charges, return an empty box.
if (charges.size() <= 0) return new BoundingBox(0, 0, 0, 0, 0, 0);
if (cachedBounds == null) {
// Start with the box of the first charge.
Charge c = charges.get(0);
double ext = Math.abs(c.w);
double corr = 1.0 + (0.1 / hardness); // see note
cachedBounds =
new BoundingBox(
new Vec3(c.x - ext, c.y - ext, c.z - ext).times(corr),
new Vec3(c.x + ext, c.y + ext, c.z + ext).times(corr));
// A note on "corr":
// As blobs are blobby, we can't use their weight/radius
// directly. This would result in unwanted cut-off's. To
// correct this, we extend the bounding box of a charge "a
// bit". That "bit" can be smaller if the charge is harder.
// Iteratively add the remaining charges.
for (int i = 1; i < charges.size(); i++) {
c = charges.get(i);
ext = Math.abs(c.w);
corr = 1.0 + (0.1 / hardness);
cachedBounds.extend(
new BoundingBox(
new Vec3(c.x - ext, c.y - ext, c.z - ext).times(corr),
new Vec3(c.x + ext, c.y + ext, c.z + ext).times(corr)));
}
}
return cachedBounds;
}
@Override
public double getFieldValue(double x, double y, double z, double size, double time) {
double sum = 0.0, dist;
double val;
for (Charge c : charges) {
// Distances.
dist = c.getDist(x, y, z);
// Calculate value.
// Actually, this is: weight * (1.0 / distance)
// But we start with the square of it to save the
// calculation of a square root.
val = (c.w * c.w) / dist;
// This charge's "hardness".
val = Math.pow(val, hardness);
// Revert divisions by zero and the like.
if (Double.isNaN(val) || Double.isInfinite(val)) continue;
// Additive or subtractive charge.
if (c.w >= 0.0) sum += val;
else sum -= val;
}
return sum;
}