* 0, but if you are doing uncommon things, you might use different values.
*/
public static Effector byAge (final Interpolator interp,
final float startAlpha, float endAlpha) {
final float rangeAlpha = endAlpha - startAlpha;
return new Effector() {
@Override public void apply (int index, float[] data, int start, float now, float dt) {
float alpha = interp.apply(
startAlpha, rangeAlpha, now - data[start + BIRTH], data[start + LIFESPAN]);
float red = Color.decodeLower(data[start + ALPHA_RED]);
data[start + ALPHA_RED] = Color.encode(alpha, red);