const int64_t start_sample = min(max((int64_t)floor(start),
(int64_t)0), last_sample);
const int64_t start_sample = min(max((int64_t)floor(start),
(int64_t)0), last_sample);
(int64_t)0), last_sample);
if (samples_per_pixel < EnvelopeThreshold)
(int64_t)0), last_sample);
if (samples_per_pixel < EnvelopeThreshold)