koobas.hobune.stream
Spiral galaxy math
I am creating a spinning galaxy made of blocks(for now, just so I can see where the 'systems' would be.)
I have been fiddling with this for a few days. Honestly don't know what I will do with it, just thought it would be fun to do. Learning a bit about rotations and such.
I have this so far:
public int numberArms = 6;
public int numberStars = 1000;
public float galaxyRadius = 500f;
public int spread = 100;
float fHatRandom (float fRange)
{
float fArea = 4 * Mathf.Atan (6.0f);
float fP = fArea * Random.value;
return Mathf.Tan (fP / 4) * fRange / 6.0f;
}
float fLineRandom (float fRange)
{
float fArea = fRange * fRange / 2;
float fP = fArea * Random.value;
return fRange - Mathf.Sqrt (fRange * fRange - 2 * fP);
}
// Use this for initialization
void Start ()
{
Random.seed = 100;
int starsPerArm = numberStars / numberArms;
float fAngularSpread = spread / numberArms;
float fArmAngle = (360 / numberArms);
for (int arm = 0; arm < numberArms; arm++)
{
for (int i = 0; i < starsPerArm; i++)
{
float fR = fHatRandom (galaxyRadius);
float fQ = fLineRandom (fAngularSpread);
float fK = 1;
float fA = numberArms * (fArmAngle);
float fX = fR * Mathf.Cos (Mathf.Deg2Rad * (fA + fR * fK + fQ));
float fY = fR * Mathf.Sin (Mathf.Deg2Rad * (fA + fR * fK + fQ));
Vector3 starPos = new Vector3 (fX, fY, arm*4);
Collider[] colliders = Physics.OverlapSphere (starPos, 1);
if (colliders.Length == 0)
{
GameObject star = GameObject.CreatePrimitive (PrimitiveType.Cube);
star.transform.position = starPos;
star.transform.parent = transform;
} else
{
i--;//because they overlapped, we try again.
}
}
}
}
// Update is called once per frame
void Update ()
{
transform.Rotate(0,0,-0.1f);
}
I have a picture of what it produces but unity is being odd about letting me post it.
As it works right now, it creates the spiral arm of the galaxy just fine. But as you can see, I just set the position of the arm to be stacked on the other arms because I cannot for the life of me figure out how to get them to rotate around the center, for that matter my center seems to be off.
I admittedly have the math skills of a gnat and have been fumbling my way through this, can someone help correct the math and get the arms/center where they belong?
If you want to test the code, just make a new class and drop it on an object, nothing else is required.
I tried, it gives me an un-usable square with 1/10th of my picture visible in it. It just floats there...waiting for something.
You might find this helpful: http://wiki.unity3d.com/index.php/Particle_Spiral_Effect
You might want to create arm under one game object, then instantiate that arm (will copy the child stars), but use a different angle for each arm.
But to alter this code, try something like this:
float fA = numberArms (fArmAngle arm);
Saw that one and looked at it, just didn't feel like redoing all my code when I was only needing a modification to my math.
Also, that is actually the answer, kind of. What I needed was float fA = arm*fArmAngle;
Will mark your answer as correct since you got the closest and were kind enough to try.
All the math you can eat:
http://www.kof.zcu.cz/st/dis/schwarzmeier/galaxy_models.html
That actually gave me a headache just reading the first paragraph. But thanks, will keep if for someday when I am gifted with the ability to read it.
maybe that is what you want....anyway, tnks for the code.
public int numberArms = 6;
public int numberStars = 1000;
public float galaxyRadius = 500f;
public int spread = 100;
float fHatRandom(float fRange)
{
float fArea = 4 * Mathf.Atan(6.0f);
float fP = fArea * Random.value;
return Mathf.Tan(fP / 4) * fRange / 6.0f;
}
float fLineRandom(float fRange)
{
float fArea = fRange * fRange / 2;
float fP = fArea * Random.value;
return fRange - Mathf.Sqrt(fRange * fRange - 2 * fP);
}
// Use this for initialization
void Start()
{
Random.seed = 100;
int starsPerArm = numberStars / numberArms;
float fAngularSpread = spread / numberArms;
float fArmAngle = (360 / numberArms);
for (int arm = 0; arm < numberArms; arm++)
{
for (int i = 0; i < starsPerArm; i++)
{
float fR = fHatRandom(galaxyRadius);
float fQ = fLineRandom(fAngularSpread);
float fK = 1;
//float fA = numberArms * (fArmAngle);
float fA = arm * fArmAngle;
float fX = fR * Mathf.Cos(Mathf.Deg2Rad * (fA + fR * fK + fQ));
float fY = fR * Mathf.Sin(Mathf.Deg2Rad * (fA + fR * fK + fQ));
Vector3 starPos = new Vector3(fX, fY, arm * 4);
Collider[] colliders = Physics.OverlapSphere(starPos, 15);
if (colliders.Length == 0)
{
GameObject star = GameObject.CreatePrimitive(PrimitiveType.Cube);
star.transform.position = starPos;
star.transform.parent = transform;
Debug.Log(starPos);
}
else
{
i--;//because they overlapped, we try again.
}
}
}
}
