Mesh Processing Library


This GitHub package contains a C++ library and several application programs that demonstrate mesh processing technologies published in research papers at ACM SIGGRAPH in 1992–1998:

The source code follows modern C++11 style and is designed for cross-platform use.

Version history

2016-04-28 — initial release.

Requirements / dependencies

The source code can be compiled with Microsoft Visual Studio 2015 from the included solution (*.sln) and project (*.vcxproj) files, using either the Integrated Development Environment (IDE) or the msbuild command.

On Unix-based platforms (including Linux, Mac OS, and Cygwin), the code can also be compiled using gcc and clang compilers (and Visual Studio cl compiler) using Makefiles designed for GNU make.

Reading/writing of images and videos is enabled using several options. If available, image I/O can use libpng/libjpeg or Windows Imaging Component (WIC). Video I/O can use Windows Media Foundation (WMF). Across all platforms, if the command ffmpeg is present in the PATH, it is spawned in a piped subprocess for both image and video I/O.

On Mac OS X, it is necessary to install XQuartz for X11 support and ffmpeg for image/video I/O.

Code compilation

Compiling using the Microsoft Visual Studio IDE

Open the distrib.sln file and build the solution (typically using the "ReleaseMD - x64" build configuration). Executables are placed in the bin, bin/debug, bin/Win32, or bin/Win32/debug directory, depending on the build configuration (64-bit versus 32-bit, and release versus debug).

Compiling using msbuild

Set the appropriate environment variables and run msbuild, e.g.:

PATH=C:\Program Files (x86)\MSBuild\14.0\Bin;%PATH%
msbuild -nologo -verbosity:minimal distrib.sln -maxcpucount:4 -p:PlatformToolset=v140 -p:platform=x64 -p:configuration=ReleaseMD

(Some alternatives are to set platform to Win32, or configuration to DebugMD, Release, or Debug; here MD stands for multithreaded DLL.) Executables are placed in the same target directory as in the IDE.

Compiling using GNU make

The CONFIG environment variable determines which make/Makefile_config_* definition file is loaded. On Windows, CONFIG can be chosen among {win, w32, cygwin, mingw, mingw32, clang}, defaulting to win if undefined. On Unix-derived platforms (including Linux and Mac OS), CONFIG=unix is the unique and default setting.

For example, to build using the Microsoft cl compiler (Debug, with 8 parallel processes, placing *.exe into directory bin/win):

make -j8

To build all programs (into either bin/unix or bin/win) and run all unit tests:

make -j test

To build on Unix, forcing the use of the gcc compiler (the alternative is clang):

make CC=gcc -j

To build just the main library using the mingw gcc compiler on Windows:

make CONFIG=mingw -j libHh

To build the Filtermesh program (into bin/clang) using the clang compiler on Windows:

make CONFIG=clang -j Filtermesh

To build all programs (into bin/cygwin) and run all demos using the gcc compiler under Cygwin:

make CONFIG=cygwin -j demos

To clean up all files in all configurations:

make CONFIG=all -j deepclean

Note that additional options such as debug/release, 32-bit/64-bit, and compiler tool paths/parameters are set in the various make/Makefile_* files. These need to be adjusted depending on the versions and installation paths of the tools. For instance, the line "rel ?= 0" in make/Makefile_config_win specifies a debug (non-release) build, and "$(call prepend_PATH,...)" in make/Makefile_base_vc sets the compiler directory.

Publications and associated programs/demos

Hugues Hoppe, Tony DeRose, Tom Duchamp, John McDonald, Werner Stuetzle.
ACM SIGGRAPH 1992 Proceedings, 71-78.
Signed-distance field estimated from a set of unoriented noisy points.
programs: Recon
demos: create_recon_*.{sh,bat}, view_recon_*.{sh,bat}
Hugues Hoppe, Tony DeRose, Tom Duchamp, John McDonald, Werner Stuetzle.
ACM SIGGRAPH 1993 Proceedings, 19-26.
Traversing the space of triangle meshes to optimize model fidelity and conciseness.
programs: Meshfit
demos: create_recon_*, view_recon_*, create_simplified_using_meshopt, view_simplified_using_meshopt
Hugues Hoppe, Tony DeRose, Tom Duchamp, Michael Halstead, Hubert Jin, John McDonald, Jean Schweitzer, Werner Stuetzle.
ACM SIGGRAPH 1994 Proceedings, 295-302.
Subdivision surfaces with sharp features, and their automatic creation by data fitting.
programs: Subdivfit
demos: create_recon_cactus, view_recon_cactus
Hugues Hoppe.
ACM SIGGRAPH 1996 Proceedings, 99-108.
Efficient, lossless, continuous-resolution representation of surface triangulations.
demos: create_geomorphs, view_geomorphs
Hugues Hoppe.
Computers & Graphics, 22(1), 1998, 27-36.
Progressive mesh data structures compatible with GPU vertex buffers.
programs: FilterPM, G3dOGL
demos: create_pm_club, view_pm_club, determine_approximation_error
Hugues Hoppe.
ACM SIGGRAPH 1997 Proceedings, 189-198.
Lossless multiresolution structure for incremental local refinement/coarsening.
programs: FilterPM, G3dOGL
demos: create_sr_office, view_sr_office
Hugues Hoppe.
IEEE Visualization 1998 Conference, 35-42.
Visually smooth adaptation of mesh refinement using cascaded temporal geomorphs.
programs: StitchPM, G3dOGL
demos: create_terrain_hierarchy, view_terrain_hierarchy, create_sr_terrain, view_sr_terrain, view_gcanyon_*
Jovan Popovic, Hugues Hoppe.
ACM SIGGRAPH 1997 Proceedings, 217-224.
Progressive encoding of both topology and geometry.
programs: G3dOGL
demos: view_psc_drumset


After the code is compiled, the demos can be run as follows.

In Windows, create, view, and clean up all the results using the batch scripts


On Unix-based systems (e.g. Linux, Mac OS, Cygwin), either run the bash scripts


or alternatively (and faster), invoke make to create all results in parallel and then view them sequentially:

make [CONFIG=config] -j demos   # config ∈ {unix, win, w32, cygwin, mingw, mingw32, clang}

Note that pressing the Esc key closes any open program window.

Filter programs

All programs recognize the argument --help (or -?) to show their many options.

The programs Filterimage, Filtermesh, Filtervideo, FilterPM, and Filterframe are all designed to:

For example, the command

Filterimage demos/data/gaudipark.png -rotate 20 -cropleft 100 -cropright 100 -filter lanczos6 -scaletox 100 -color 0 0 255 255 -boundary border -cropall -20 -setalpha 255 -color 0 0 0 0 -drawrectangle 30% 30% -30% -30% -gdfill -info -to jpg >

As another example, the command

FilterPM demos/data/ -info -nfaces 1000 -outmesh |
Filtermesh -info -signeddistcontour 60 -genus |
G3dOGL -key DmDe

The command

FilterPM demos/data/ -nf 2000 -outmesh |
Filtermesh -angle 35 -silsubdiv -silsubdiv -mark |
G3dOGL -key DmDeDbJ---- -st demos/data/spheretext.s3d

The command

Filtervideo demos/data/palmtrees_small.mp4 -filter keys -scaleu 1.5 >palmtrees_small.scale1.5.mp4

The command

Filtervideo demos/data/palmtrees_small.mp4 -info -trimbeg 4 -boundary clamped -trimend -20% -tscale 1.5 -framerate 150% -croprectangle 50% 50% 400 240 -gamma 1.5 -bitrate 10m |
VideoViewer demos/data/palmtrees_small.mp4 - -key =an

Surface reconstruction


This program reads a list of 3D (x, y, z) points assumed to be sampled near some unknown manifold surface, and reconstructs an approximating triangle mesh. For example,

Recon <demos/data/distcap.pts -samplingd 0.02 |
Filtermesh -genus -rmcomp 100 -fillholes 30 -triangulate -genus | tee distcap.recon.m |
G3dOGL -st demos/data/distcap.s3d -key DmDe

To show the progression of the Marching Cubes algorithm,

Recon <demos/data/distcap.pts -samplingd 0.02 -what c |
Filtera3d -split 30 | G3dOGL -key DCDb -st demos/data/distcap_backside.s3d -terse

To show a similar streaming reconstruction of the surface mesh,

Recon <demos/data/distcap.pts -samplingd 0.02 -what m | Filtermesh -toa3d |
Filtera3d -split 30 | G3dOGL demos/data/distcap.pts -key DCDb -st demos/data/distcap_backside.s3d -terse -input -key _Jo

The same program can also read a list of 2D (y, z) points to reconstruct an approximating curve:

Recon <demos/data/curve1.pts -samplingd 0.06 -grid 30 |
Filtera3d -joinlines | tee curve1.a3d |
G3dOGL demos/data/curve1.pts -input -st demos/data/curve1.s3d


Given an initial mesh and a list of 3D points, this program optimizes both the mesh connectivity and geometry to improve the fit, i.e. minimizing the squared distances from the points to the surface. For example,

Meshfit -mfile distcap.recon.m -file demos/data/distcap.pts -crep 1e-5 -reconstruct |
tee distcap.opt.m | G3dOGL -st demos/data/distcap.s3d -key DmDe

The input points can also be sampled from an existing surface, e.g.:

Filtermesh demos/data/blob5.orig.m -randpts 10000 -vertexpts |
Meshfit -mfile demos/data/blob5.orig.m -file - -crep 1e-6 -simplify |
G3dOGL -st demos/data/blob5.s3d -key DmDe

To view the real-time fitting optimization,

Meshfit -mfile distcap.recon.m -file demos/data/distcap.pts -crep 1e-5 -outmesh - -record -reconstruct | G3dOGL -st demos/data/distcap.s3d -key DmDeDC -async -terse


This related program performs a similar optimization of a 1D polyline (either open or closed) to fit a set of 2D points. For example,

Polyfit -pfile curve1.a3d -file demos/data/curve1.pts -crep 3e-4 -spring 1 -reconstruct |
G3dOGL demos/data/curve1.pts -input -st demos/data/curve1.s3d


In a subdivision surface representation, a coarse base mesh tagged with sharp edges defines a piecewise smooth surface as the limit of a subdivision process. Such a representation both improves geometric fidelity and leads to a more concise description.

Filtermesh distcap.opt.m -angle 52 -mark |
Subdivfit -mfile - -file demos/data/distcap.pts -crep 1e-5 -csharp .2e-5 -reconstruct >distcap.sub0.m

To view the result,

G3dOGL distcap.sub0.m "Subdivfit -mf distcap.sub0.m -nsub 2 -outn |" -st demos/data/distcap.s3d -key NDmDe -hwdelay 5 -hwkey N


This program computes measures of differences between two meshes. It samples a dense set of points from a first mesh and computes the projections of each point onto the closest point on a second mesh.

MeshDistance -mfile distcap.recon.m -mfile distcap.opt.m -bothdir 1 -maxerror 1 -distance

Mesh simplification

Given a mesh, MeshSimplify applies a sequence of edge collapse operations to simplify it to a coarse base mesh while trying to best preserve the appearance of the original model. It supports many different simplification criteria, as well as face properties, edges tagged as sharp, and vertex and corner attributes (nx,ny,nz normals, r,g,b colors, and u,v texture coordinates).

For example,

MeshSimplify demos/data/club.orig.m -prog club.prog -simplify >club.base.m

The next step is to reverse the sequence of stored edge collapses, i.e. forming a progressive sequence of vertex splits:

reverselines club.prog >club.rprog

We construct a concise progressive mesh by encoding the base mesh together with the sequence of vertex splits that exactly recover the original mesh:

Filterprog -fbase club.base.m -fprog club.rprog -pm_encode >

The complete process from the original mesh to the progressive mesh is implemented by the script call

demos/bin/meshtopm.{sh,bat} demos/data/club.orig.m >

Given a progressive mesh, we can interactively traverse its continuous levels of detail:

G3dOGL -pm_mode -st demos/data/club.s3d -lightambient .4

We can also define geomorphs between discrete levels of detail, e.g.

FilterPM -nfaces 2000 -geom_nfaces 3300 -geom_nfaces 5000 -geom_nfaces 8000 |
G3dOGL -st demos/data/club.s3d -key SPDeN -lightambient .5 -thickboundary 1 -video 101 - | VideoViewer - -key m

This example displays a progressive mesh after truncating all detail below 300 faces and above 10000 faces:

FilterPM demos/data/ -nf 300 -truncate_prior -nf 10000 -truncate_beyond |
G3dOGL -pm_mode - -st demos/data/standingblob.s3d

As an example of simplifying meshes with appearance attributes,

Filterimage demos/data/gaudipark.png -scaletox 200 -tomesh |
MeshSimplify - -nfaces 4000 -simplify |
G3dOGL -st demos/data/imageup.s3d -key De -lightambient 1 -lightsource 0

Selective view-dependent mesh refinement

Within demos/create_sr_office, the script call

demos/bin/meshtopm.{sh,bat} demos/data/office.nf80000.orig.m -vsgeom >

creates a progressive mesh in which the simplified vertices are constrained to lie at their original positions (-vsgeom). This enables selective refinement, demonstrated by

G3dOGL -eyeob demos/data/unit_frustum.a3d -sr_mode -st demos/data/office_srfig.s3d -key ,DnDeDoDb -lightambient .4 -sr_screen_thresh .002 -frustum_frac 2

The mesh is adaptively refined within the view frustum, shown as the inset rectangle (key Do) or in the top view (key Dr). Drag the mouse buttons to rotate, pan, and dolly the object.

Terrain level-of-detail control

Within demos/create_sr_terrain.{sh,bat},

Filterimage demos/data/ -tobw -elevation -step 6 -scalez 0.000194522 -removekinks -tomesh |
Filtermesh -assign_normals >gcanyon_sq200.orig.m
demos/bin/meshtopm.{sh,bat} gcanyon_sq200.orig.m -vsgeom -terrain >

Then, within demos/,

(common="-eyeob demos/data/unit_frustum.a3d -sr_mode -st demos/data/gcanyon_fly_v98.s3d -texturemap demos/data/gcanyon_color.1024.png -key DeDtDG -sr_screen_thresh .02292 -sr_gtime 64 -lightambient .5"; \
export G3D_REV_AUTO=1; \
G3dOGL $common -geom 800x820+100+10 -key "&O" -key ,o----J |
G3dOGL $common -geom 800x820+920+10 -async -killeof -input -key Dg)

For large terrain meshes, we form a hierarchical progressive mesh by partitioning the terrain mesh into tiles, simplifying each tile independently to form a progressive mesh, stitching the progressive meshes together 2-by-2, and recursively simplifying and merging at coarser pyramid levels.

An example is presented in demos/create_terrain_hierarchy. It makes use of

StitchPM -rootname terrain.level0 -blockx 2 -blocky 2 -blocks 32 -stitch >

to assemble each 2-by-2 set of progressive mesh tiles terrain.level0.x{0,1}.y{0,1}.pm at the finest level.

The script demos/view_gcanyon_interactive launches an interactive flythrough over a Grand Canyon terrain model, using a progressive mesh precomputed from an original 4096×2048 height field.

Alternatively, demos/view_gcanyon_frames shows a real-time flythrough using a pre-recorded flight path, whereby keystroke commands embedded within the input stream automatically change viewing modes.

Topology simplification

The program MinCycles removes topological noise from a mesh by iteratively pinching off the smallest nonseparating cycle of edges until a specified criterion (cycle length, number of cycle edges, number of cycles, or mesh genus) is reached.

For example, within demos/create_topologically_simplified.{sh,bat},

FilterPM demos/data/ -nf 200000 -outmesh |
MinCycles - -fraccyclelength 1.2 -maxcyclelen .10 -closecycles |
G3dOGL -st demos/data/office.s3d -key DeDEJ---- -thickboundary 0 -lightambient .9

Geometry viewer

The G3dOGL program shows interactive rasterized renderings of 3D (and 2D) geometry, represented as

Please see the many examples presented earlier. The viewer can also read *.frame elements to position the viewer and the objects in world space. Elements of *.a3d, *.m, and *.frame streams can all be interleaved in a single input stream.

The viewer can take image snapshots (see demos/create_rendered_mechpart_image) and record videos (see demos/create_rendered_mechpart_video).

The mouse/keyboard UI controls include:

   Mouse movements:
   left mouse:          rotate
   middle mouse:        pan
   right mouse:         dolly
   shift-left:          pan
   shift-middle mouse:  roll
   shift-right mouse:   zoom
   (mouse movements are with respect to current object; see '0-9' below)
   Important key strokes:
   ? : print complete list of keys
   D?: print list of keys prefixed by 'D'
   De: toggle edges
   Ds: toggle shading of faces
   Db: toggle backface culling
   Dm: toggle Gouraud/flat shading
   DP: save current window as an image file
   DS: toggle show some sliders
   S : toggle show some other sliders
   j : jump to a default viewpoint
   J : automatically rotate object
   D/: edit viewpoint filename
   , : read the viewpoint
   . : save the viewpoint
   0-9: select object (0=eye_frame, 1=first object, 2=second object...)
   u : display/hide current object
   N : select next object
   P : select previous object
   -=: decrease/increase the magnitude of all movements
   f : toggle flying (usually with '0' eye selected)

To record a 6-second (360-frame) video of a rotating mesh and then view the resulting video:

G3dOGL demos/data/standingblob.orig.m -st demos/data/standingblob.s3d -key iioJ -video 360 output_video.mp4
VideoViewer output_video.mp4

The related program G3dVec shows wireframe hidden-line-removed renderings of *.a3d streams and *.m meshes. It can write vector-based Postscript figures (see demos/view_hidden_line_removed).

In both programs, the keys ? and D? show a list of available keyboard commands.

Image/video viewer

The VideoViewer program enables interactive viewing and simple editing of both images and videos. Again, the key ? shows a list of available keyboard commands. Press pageup/pagedown to quickly browse through the videos and/or images in a directory. Audio is not currently supported.

File formats

Mesh (*.m)

See the documentation at the end of libHh/GMesh.h

A mesh is a set of vertices and faces. These in turn also define edges and corners. Arbitrary string tuples can be associated with vertices, faces, edges, and corners. Examples of string tuples: {normal=(.1 .2 .3) rgb=(1 1 1) matid=5 material="string"}. See the several demos/data/*.m files for examples of the mesh format. Note that the indices of vertices and faces start at 1 instead of 0; in hindsight that was a poor choice.

Geometry stream (*.a3d, *.pts)

See the documentation at the end of libHh/A3dStream.h

The stream contains polygons, polylines, points, and control codes (like end-of-frame, end-of-input, change-of-object). Unlike in a mesh, these primitives do not share vertices. The stream can be either text or binary.

Frame stream (*.frame, *.s3d)

See the documentation at the end of libHh/FrameIO.h

This text or binary format encodes a 4×3 affine transformation (plus an object id and a scalar field-of-view zoom). It is used to record default viewing configurations, and sequences of frames for flythroughs. It usually represents the linear transform from object space (or eye space) to world space. The stream can be either text or binary.

Progressive mesh (*.pm)

This is a binary representation that consists of a coarse base mesh and a sequence of vertex split records.

Edge collapse / vertex split records (*.prog, *.rprog)

These are temporary text files containing verbose information for a sequence of edge collapse / vertex split records used by MeshSimplify / reverselines / Filterprog to create a progressive mesh.


The library libHh contains the main reusable classes. All files include Hh.h which sets up a common cross-platform environment.

The libraries libHWin and libHWX define different implementations of a simple windowing interface (class HW), under Win32 and X Windows, respectively. Both implementations support OpenGL rendering.

Code details

The include file libHh/RangeOp.h defines many functions that act on ranges, which are containers or views for which begin() and end() are defined. For example, the function call hh::fill(ar, 1.f) assigns the value 1.f to all elements in the array named ar, and the function call hh::mean(matrix) computes the average value of all entries in the named matrix.

The debugging macro SHOW(expr) outputs expr = ... on std::cerr and also returns expr. It also accepts multiple arguments in which case it returns void. For example, SHOW(min(1, 2), "hello", 3*2) outputs the line min(1, 2)=1 hello 3*2=6. Note the special treatment of literal string values.

Unicode strings are stored using UTF-8 encoding into ordinary std::string variables. The functions hh::widen() and hh::narrow() convert to and from the std::wstring UTF-16 encodings used in Win32 system calls.

All files use end-of-line encodings based on Unix '\n' LF (rather than DOS '\r\n' CR+LF). All streams are opened in binary mode. This allows text and binary to coexist in the same file.


See the file ./license.txt.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact with any additional questions or comments.