void *create_randomness(uint64_t n, std::vector<T> &rand) {
// Prepare n bits of randomness using a pseudo-random number generator.
// A vector instead of a raw array is used to store the data because
// this way, it's easier for the caller to keep track of the allocation.
std::uniform_int_distribution<T>
distribution(0, std::numeric_limits<T>::max());
std::mt19937 mt_engine(42);
auto generator = std::bind(distribution, mt_engine);
uint64_t num_chunks = n/sizeof(rand[0])+1;
rand.reserve(num_chunks);
for (auto i = 0; i < num_chunks; i++) {
rand[i] = generator();
}
return (&rand[0]);
}
void GLLensDustFilter::UpdateNoise() {
SPADES_MARK_FUNCTION();
noise.resize(128 * 128);
uint32_t rnd = mt_engine();
rnd ^= 0x7abd4513;
for(size_t i = 0; i < 128 * 128; i++) {
noise[i] = rnd;
rnd = (rnd * 0x71931) + 0x981f311;
if(rnd == 0xffffffff) // mod 2^32-1
rnd = 0;
}
IGLDevice *dev = renderer->GetGLDevice();
dev->BindTexture(IGLDevice::Texture2D, noiseTex);
dev->TexSubImage2D(IGLDevice::Texture2D,
0, 0, 0, 128, 128,
IGLDevice::BGRA, IGLDevice::UnsignedByte,
noise.data());
}