403: Mesh simplification

This tutorial explains how to:

• Simplify the surface mesh using the SurfaceMeshSimplification class.

• Visualize the original and simplified meshes side-by-side using MultiViewer.

Mesh simplification is a crucial process in computer graphics and geometry processing. It reduces the number of vertices and faces in a 3D mesh while preserving its overall structure and visual appearance. This technique is widely used in:

• Real-time rendering (e.g., games and VR applications).

• Reducing storage and computational requirements.

• Level-of-detail (LOD) modeling in computer graphics.

Number of vertices in the input mesh: 15447
Number of vertices in the simplified mesh: 333

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# sphinx_gallery_thumbnail_path = '_static/sphx_glr_tutorial_403_mesh_simplification_thumb.png'

# -------------------------------------------------------------------------------
# Adding Easy3D Python Bindings to the System Path
# -------------------------------------------------------------------------------
# This is required if the bindings are not installed via `pip` but are located in
# a local build directory. For building and installing Python bindings of Easy3D,
# please refer to: https://github.com/LiangliangNan/Easy3D/blob/main/README.md
# -------------------------------------------------------------------------------
import sys
sys.path.append("../../cmake-build-release/lib/python")  # Update this path to point to your Easy3D build directory.

# Import Easy3D for 3D geometry processing and visualization.
import easy3d
from easy3d import SurfaceMeshIO, SurfaceMeshSimplification

# Setting `True` will provide detailed output for debugging purposes.
easy3d.initialize(False)

# Load a 3D surface mesh file using the `SurfaceMeshIO` class.
# Here, we use the Stanford Bunny model,
mesh = SurfaceMeshIO.load(easy3d.resource_directory() + "/data/bunny.ply")
# Print details about the original mesh.
print(f"Number of vertices in the input mesh: {mesh.n_vertices()}")

# -----------------------------------------------------------------------------
# Simplify the Surface Mesh
# -----------------------------------------------------------------------------
# The `SurfaceMeshSimplification` class simplifies a 3D mesh by reducing the number
# of vertices and faces while preserving important geometric features.

# To compare the original and simplified meshes, we make a copy of the input mesh.
copied_mesh = easy3d.SurfaceMesh(mesh)  # Create a copy for simplification.

# Initialize the mesh simplifier.
simplifier = SurfaceMeshSimplification(copied_mesh)

# Set the target number of vertices to 333 (you can play with this parameter)
simplifier.simplify(333)

# Print details about the simplified mesh.
print(f"Number of vertices in the simplified mesh: {copied_mesh.n_vertices()}")

# -----------------------------------------------------------------------------
# Visualize Original and Simplified Meshes Side-by-Side
# -----------------------------------------------------------------------------
# Use the `MultiViewer` class to create a side-by-side comparison of the meshes.

# Create a MultiViewer instance with 1 row and 2 columns.
viewer = easy3d.MultiViewer(1, 2, "Easy3D Viewer - Mesh simplification")

# Add the original mesh to the viewer.
viewer.add_model(mesh)
viewer.assign(0, 0, mesh)  # Assign it to the left view (row=0, column=0).

# Add the simplified mesh to the viewer.
viewer.add_model(copied_mesh)
viewer.assign(0, 1, copied_mesh)  # Assign it to the right view (row=0, column=1).

# Add instructions for the viewer (optional).
viewer.set_usage("",
    "Left view: Original mesh\n"
    "Right view: Simplified mesh"
)

# Set the camera view direction and up vector for a better view position.
viewer.camera().setViewDirection(easy3d.vec3(0, 1, 0))   # Set the view direction.
viewer.camera().setUpVector(easy3d.vec3(0, 0, 1))        # Set the up vector.

# The bunny model included in Easy3D has a per-face scalar property, which will be rendered by
# default. To better reveal the effect of simplification, let's show the bunny with a uniform color.
mesh.renderer().get_triangles_drawable("faces").set_coloring_method(easy3d.State.UNIFORM_COLOR)
copied_mesh.renderer().get_triangles_drawable("faces").set_coloring_method(easy3d.State.UNIFORM_COLOR)

# By default, the edges/wireframes of a surface mesh is hidden. Let's also show them.
mesh.renderer().get_lines_drawable("edges").set_visible(True)
copied_mesh.renderer().get_lines_drawable("edges").set_visible(True)

# Launch the viewer.
viewer.run()