Merge pull request #14 from GazzolaLab/example-euler

Example Case: Rendering spring action for rigid rod

examples/single_rigid_rod_spring_action.py

@@ -0,0 +1,55 @@
+import numpy as np
+
+import bsr
+
+bsr.clear_mesh_objects()
+
+# Environment configuration
+k = 5  # spring constant
+
+
+def f(x):
+    y, v = x[0], x[1]
+    return np.array([v, (-1) * (k) * (y)])
+
+
+def euler_forward_step(x, f, dt):
+    return x + f(x) * dt
+
+
+# Rod configuration
+N = 5
+velocity = np.arange(20, 45, N)  # initial z-velocities
+position = np.stack(
+    [
+        np.zeros(N),  # x
+        np.zeros(N),  # y
+        np.linspace(0, 10, N),  # z
+    ],
+    axis=0,
+)  # (3, 5)
+radius = 0.2 * np.ones(N)  # radius of the rod
+
+rod = bsr.rod()
+rod.update(keyframe=0, positions=position, radius=radius)
+
+
+####### SIMULATION ########
+# Simulation parameters
+
+dt = 10 ** (-3)
+framerate = 25
+simulation_ratio = int(1 / framerate / dt)
+time = np.arange(0, 10, dt)
+
+# Euler-Forward time stepper
+for time_index, t in enumerate(time[:-1]):
+    state = np.stack([position[2], velocity], axis=0)
+    position[2] = euler_forward_step(state, f, dt)
+
+    if time_index % simulation_ratio == 0:
+        # update the rod
+        keyframe = int(time_index / simulation_ratio) + 1
+        rod.update(keyframe=keyframe, positions=position, radius=radius)
+
+bsr.save("single_rigid_rod_spring_action.blend")

src/bsr/__init__.py

@@ -1,6 +1,8 @@
 import sys
 from importlib import metadata as importlib_metadata
 
+from .macros import *
+
 
 def get_version() -> str:
     try:

src/bsr/macros.py

@@ -0,0 +1,10 @@
+__all__ = ["clear_mesh_objects"]
+
+import bpy
+
+
+def clear_mesh_objects() -> None:
+    # Clear existing mesh objects in the scene
+    bpy.ops.object.select_all(action="DESELECT")
+    bpy.ops.object.select_by_type(type="MESH")
+    bpy.ops.object.delete()