readply - a Python extension module for fast(er) import of PLY files in Blender

The default PLY importer in Blender is quite slow when it comes to importing large mesh files. Blender 3.6 introduced a new C++-based PLY importer, which is marked "experimental", see below for comparison against this importer.

Most Python-based importers suffer from slow import because during import Python data structures are built up holding all geometry, vertex colors, etc. This simply takes quite a lot of time (and memory).

Fortunately, Python objects that support the buffer protocol can be passed in certain places of the Blender Python API. We can use this functionality to pass chunks of memory containing vertex and face data, without having to build up Python data structures. We use NumPy arrays in the readply extension module to easily pass the data directly to Blender.

Example usage:

$ blender [<scene.blend>] -P mesh_readply.py -- myfile.ply

Notes:

• The readply module is not tied to Blender in any way and can be used as a general PLY reader in Python.
• Development and testing is done on Linux, but the module should compile and work under different operating systems

Performance

Below are some numbers when importing the Asian Dragon model [1] from The Stanford 3D Scanning Repository [2]. This 3D model consists of 3,609,600 vertices and 7,219,045 triangles, with the file being around 137 MB.

With Blender 3.6.5 and xyzrgb_dragon.ply already in the filesystem cache:

# Native blender PLY importer (bpy.ops.import_mesh.ply())
$ blender -P test/blender_native_import.py -- xyzrgb_dragon.ply
...
Successfully imported '/home/melis/models/stanford/xyzrgb_dragon.ply' in 40.316 sec
Imported in 40.601s (legacy)

# New experimental blender PLY importer available in 3.6+ (bpy.ops.wm.ply_import())
$ blender -P test/blender_native_import_experimental.py -- xyzrgb_dragon.ply
...
PLY import of 'xyzrgb_dragon.ply' took 1471.2 ms
Imported in 1.744s (experimental)

# mesh_readply.py using readply extension module
$ blender -P mesh_readply.py -- xyzrgb_dragon.ply
...
PLY file read by readply() in 0.774s
Blender object+mesh created in 5.812s
Total import time 6.586s

I.e. in this test the mesh_readply.py script (which uses the readply module) loads the Dragon model 6.2x faster into Blender than Blender's own legacy PLY import script, but 3.8x slower than the new experimental PLY importer. The latter appears to be mostly due to a much higher time to create the mesh from the imported data.

1. http://graphics.stanford.edu/data/3Dscanrep/xyzrgb/xyzrgb_dragon.ply.gz
2. http://graphics.stanford.edu/data/3Dscanrep/

Building

A setup.py script is provided to build the extension, either under regular Python or with Blender's included version of Python.

Note that for Blender usage it is advised to build and install the module using Blender's Python version, as that will take care of placing the module in the correct location.

Blender

Note

The official Blender binaries do not include the Python headers. So you still need a full Python installation somewhere to build the readply extension.

Run the setup.py script with Blender's copy of the Python interpreter. There should be a python3.10 executable in your Blender directory. For example, for 3.6.5 on Linux the Python binary is located at <blender-dir>/3.6/python/bin/python3.10. Then run

$ <blender-dir>/3.6/python/bin/python3.10 setup.py install

If you get an error regarding the setuptools module not being found, then run .../python3.10 -m ensurepip which should install the pip module, followed by installing the setuptools module.

An alternative way is to run the setup script under Blender:

$ blender -b -P setup.py

General Python

There's at least two options:

# Build the module, then copy it to the top-level directory
$ python setup.py build_ext --inplace

or

# Build the module, then copy it to the default Python module location
# (which might be a system-wide directory)
$ python setup.py install

Notes

• Make sure that the version of NumPy used for compiling the readply extension has the same API version as the one that is used by Blender (the official binary distributions of Blender include a version of NumPy)
• The readply extension module can be compiled for both Python 2.x and 3.x, even though Blender uses Python 3.x
• Texture coordinates may be stored in s+t or u+v vertex fields, depending on what property names the PLY file being read uses

Bugs

• The module is currently not usable as a drop-in replacement of the built-in PLY import in Blender
• It is assumed that if the PLY file includes vertex coordinates they are defined in x, y and z order (the PLY header allows properties in any order).

Author

Paul Melis ([email protected]), SURF Visualization team

The files under the rply/ directory are a copy of the RPly 1.1.4 source distribution (see http://w3.impa.br/~diego/software/rply/).

License

See the LICENSE file in the root directory of this distribution, which applies to all files except the ones in the rply/ directory.

See rply/LICENSE for the the license of the RPly sources.