void Generator::computeStarPositions(InputVertices& destination, unsigned limit, unsigned seed) {
InputVertices* vertices = & destination;
//_limit = limit;
QElapsedTimer startTime;
startTime.start();
srand(seed);
vertices->clear();
vertices->reserve(limit);
const unsigned MILKY_WAY_WIDTH = 12.0; // width in degrees of one half of the Milky Way
const float MILKY_WAY_INCLINATION = 0.0f; // angle of Milky Way from horizontal in degrees
const float MILKY_WAY_RATIO = 0.4f;
const unsigned NUM_DEGREES = 360;
for(int star = 0; star < floor(limit * (1 - MILKY_WAY_RATIO)); ++star) {
float azimuth, altitude;
azimuth = (((float)rand() / (float) RAND_MAX) * NUM_DEGREES) - (NUM_DEGREES / 2);
altitude = (acos((2.0f * ((float)rand() / (float)RAND_MAX)) - 1.0f) / PI_OVER_180) + 90;
vertices->push_back(InputVertex(azimuth, altitude, computeStarColor(STAR_COLORIZATION)));
}
for(int star = 0; star < ceil(limit * MILKY_WAY_RATIO); ++star) {
float azimuth = ((float)rand() / (float) RAND_MAX) * NUM_DEGREES;
float altitude = powf(randFloat()*0.5f, 2.0f)/0.25f * MILKY_WAY_WIDTH;
if (randFloat() > 0.5f) {
altitude *= -1.0f;
}
// we need to rotate the Milky Way band to the correct orientation in the sky
// convert from spherical coordinates to cartesian, rotate the point and then convert back.
// An improvement would be to convert all stars to cartesian at this point and not have to convert back.
float tempX = sin(azimuth * PI_OVER_180) * cos(altitude * PI_OVER_180);
float tempY = sin(altitude * PI_OVER_180);
float tempZ = -cos(azimuth * PI_OVER_180) * cos(altitude * PI_OVER_180);
float xangle = MILKY_WAY_INCLINATION * PI_OVER_180;
float newX = (tempX * cos(xangle)) - (tempY * sin(xangle));
float newY = (tempX * sin(xangle)) + (tempY * cos(xangle));
float newZ = tempZ;
azimuth = (atan2(newX,-newZ) + Radians::pi()) / PI_OVER_180;
altitude = atan2(-newY, hypotf(newX, newZ)) / PI_OVER_180;
vertices->push_back(InputVertex(azimuth, altitude, computeStarColor(STAR_COLORIZATION)));
}
double timeDiff = (double)startTime.nsecsElapsed() / 1000000.0; // ns to ms
qDebug() << "Total time to generate stars: " << timeDiff << " msec";
}
void Generator::computeStarPositions(InputVertices& destination, unsigned limit, unsigned seed) {
InputVertices* vertices = & destination;
//_limit = limit;
timeval startTime;
gettimeofday(&startTime, NULL);
srand(seed);
vertices->clear();
vertices->reserve(limit);
const unsigned MILKY_WAY_WIDTH = 16.0; // width in degrees of one half of the Milky Way
const float MILKY_WAY_INCLINATION = 30.0f; // angle of Milky Way from horizontal in degrees
const float MILKY_WAY_RATIO = 0.6;
const unsigned NUM_DEGREES = 360;
for(int star = 0; star < floor(limit * (1 - MILKY_WAY_RATIO)); ++star) {
float azimuth, altitude;
azimuth = (((float)rand() / (float) RAND_MAX) * NUM_DEGREES) - (NUM_DEGREES / 2);
altitude = (acos((2.0f * ((float)rand() / (float)RAND_MAX)) - 1.0f) / PI_OVER_180) + 90;
vertices->push_back(InputVertex(azimuth, altitude, computeStarColor(STAR_COLORIZATION)));
}
for(int star = 0; star < ceil(limit * MILKY_WAY_RATIO); ++star) {
float azimuth = ((float)rand() / (float) RAND_MAX) * NUM_DEGREES;
float altitude = asin((float)rand() / (float) RAND_MAX * 2 - 1) * MILKY_WAY_WIDTH;
// we need to rotate the Milky Way band to the correct orientation in the sky
// convert from spherical coordinates to cartesian, rotate the point and then convert back.
// An improvement would be to convert all stars to cartesian at this point and not have to convert back.
float tempX = sin(azimuth * PI_OVER_180) * cos(altitude * PI_OVER_180);
float tempY = sin(altitude * PI_OVER_180);
float tempZ = -cos(azimuth * PI_OVER_180) * cos(altitude * PI_OVER_180);
float xangle = MILKY_WAY_INCLINATION * PI_OVER_180;
float newX = (tempX * cos(xangle)) - (tempY * sin(xangle));
float newY = (tempX * sin(xangle)) + (tempY * cos(xangle));
float newZ = tempZ;
azimuth = (atan2(newX,-newZ) + Radians::pi()) / PI_OVER_180;
altitude = atan2(-newY, hypotf(newX, newZ)) / PI_OVER_180;
vertices->push_back(InputVertex(azimuth, altitude, computeStarColor(STAR_COLORIZATION)));
}
qDebug("Took %llu msec to generate stars.\n", (usecTimestampNow() - usecTimestamp(&startTime)) / 1000);
}
