Update icbuilder.py

Author: TimGoTheCreator

tools/icbuilder.py

@@ -41,6 +41,48 @@ def coldPlummer(N, scale=1.0, mass=1.0, dm_fraction=0.9):
 
     return particles
 
+def disk(N, radius=10.0, mass=1.0, thickness=0.1):
+    """
+    Generates a simple equilibrium-ish exponential disk galaxy.
+    - N: number of particles
+    - radius: scale length of the disk
+    - mass: total mass of the disk
+    - thickness: vertical Gaussian thickness
+    """
+
+    particles = []
+    M = mass
+
+    for _ in range(N):
+        # Sample radius from exponential disk: p(r) ~ r * exp(-r/R)
+        u = random.random()
+        r = -radius * math.log(1 - u)
+
+        # Random angle
+        phi = 2 * math.pi * random.random()
+
+        # Position in the plane
+        x = r * math.cos(phi)
+        y = r * math.sin(phi)
+
+        # Vertical position (Gaussian)
+        z = random.gauss(0, thickness)
+
+        # Circular velocity
+        enclosed = M * (1 - math.exp(-r / radius) * (1 + r / radius))
+        v = math.sqrt(enclosed / (r + 1e-6))
+
+        # Tangential velocity
+        vx = -v * math.sin(phi)
+        vy =  v * math.cos(phi)
+
+        # Small vertical velocity dispersion
+        vz = random.gauss(0, 0.05 * v)
+
+        particles.append((x, y, z, vx, vy, vz, mass / N, 0))
+
+    return particles
+
 def disk(N, radius=10.0, mass=1.0, thickness=0.1, dm_fraction=0.9):
     """
     Exponential disk with DM halo.