12.2.1 Create a Math-Generated Wavy Plane¶
Setting up the USD stage and defining a mesh:
from pxr import Usd, UsdGeom
stage = Usd.Stage.CreateNew("wavy_plane.usda"))
UsdGeom.SetStageUpAxis(stage, UsdGeom.Tokens.y)
wavy_plane = UsdGeom.Mesh.Define(stage, "/World/wavy_plane") Define the size of the plane, the resolution of the grid, and a height function that generates the wavy surface:
import math
size = 10
resolution = 50
def get_height(x, y):
return math.sin(0.5 * x) * math.cos(0.5 * y)Generate points for the terrain surface:
points = []
for x in range(resolution):
for y in range(resolution):
xf = (x / (resolution - 1)) * (2 * size) - size
yf = (y / (resolution - 1)) * (2 * size) - size
z = get_height(xf, yf)
points.append((xf, yf, z)) Define vertex points:
faceVertexIndices = []
faceVertexCounts = []
for x in range(resolution - 1):
for y in range(resolution - 1):
i0 = x * resolution + y
i1 = i0 + 1
i2 = i0 + resolution + 1
i3 = i0 + resolution
faceVertexIndices.extend([i0, i1, i2, i3])
faceVertexCounts.append(4) Plug in all the data to the mesh:
wavy_plane.GetPointsAttr().Set(points)
wavy_plane.GetFaceVertexCountsAttr().Set(faceVertexCounts)
wavy_plane.GetFaceVertexIndicesAttr().Set(faceVertexIndices)
stage.Save() 12.2.2 Scatter Cubes on the Wavy Plane¶
Defining the cube prototype:
proto_cube_path = "/World/Prototypes/Cube"
cube = UsdGeom.Cube.Define(stage, proto_cube_path)
cube.CreateSizeAttr().Set(0.3) Generate positions to place cubes:
import random
num_instances = 100
positions = []
proto_indices = []
for _ in range(num_instances):
x = random.uniform(-size, size)
y = random.uniform(-size, size)
z = get_height(x, y)
positions.append(Gf.Vec3f(x, y, z))
proto_indices.append(0) Assign positions and indices to PointInstancer:
instancer = UsdGeom.PointInstancer.Define(stage, "/World/Instancer")
instancer.CreatePrototypesRel().SetTargets([proto_cube_path])
instancer.CreatePositionsAttr().Set(positions)
instancer.CreateProtoIndicesAttr().Set(proto_indices)
stage.Save()12.3 Complex Real Assets and additional controls¶
See the code in “./usd_scatter_addon/core/scatter.py”.
12.4 Blender Add-on¶
See the code in “./usd_scatter_addon/init.py”.