Wavefront OBJ toolbox
Read and Write Wavefront OBJ geometry and MTL files.
A Wavefront Geometry Object file is supported by many 3D programs, it looks like:
v 0.000000 2.000000 0.000000
v 0.000000 0.000000 0.000000
v 2.000000 0.000000 0.000000
v 2.000000 2.000000 0.000000
% Vertices Coordinates 4
f 1 2 3 4
% Faces 1
The function read_wobj allow Wavefront object files including material MTL files to be read into a Matlab structure.
The function write_wobj exports a Matlab structure to an OBJ file.
It doesn't matter if the object file contains splines or polygon based geometry, it reads and writes almost all .obj files.
See "help read_wobj" and "help write_wobj"
Comments and bug reports are welcome
Cite As
Dirk-Jan Kroon (2021). Wavefront OBJ toolbox (https://www.mathworks.com/matlabcentral/fileexchange/27982-wavefront-obj-toolbox), MATLAB Central File Exchange. Retrieved .
Comments and Ratings (35)
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I m Usingen your function
Write_obj
FV = isosurface(plot_data)
Write_obj(OBJ, filename)
Obj structure ist Filmen exactly like example
The Resultat ist NOT the same AS isosurface ( not at all)
The Input plot_data ist 512x512x256
Maybe somebody
Knows whatsapp wrong
Christian
Can someone explain how to export .fig file to .obj? I am trying but still can not figured it out.
I tried loading a 25 MB obj file, and it died with the following error (after a pretty long time reading, actually):
Reading Object file : C:/Volpe/Data/SBS-Photogrammetry//textured-mesh.obj/textured-mesh.obj
%
% OBJ File Generated by Meshlab
%
% Object textured-mesh.obj
%
% Vertices: 110345
% Faces: 220485
%
Reading Material file : C:\Volpe\Data\SBS-Photogrammetry\Dense_Pickett_4_Chris\textured-mesh.obj\textured-mesh.obj.mtl
%
% Wavefront material file
% Converted by Meshlab Group
%
Finished Reading Material file
Subscripted assignment dimension mismatch.
Error in read_wobj (line 90)
vertices(nv,1:4)=data;
K>>
In this case, "data" is a 1x6 array of doubles, and the code is trying to squeeze it into four columns.
thanqq soo much sir
If you export the .obj with a material library .mtl file that is in a subdirectory, the .obj file will try to import the library using the line "mtllib <subdirectory>/<material name>.mtl". The .mtl file seems to always be generated in the same directory as the .obj file, so when you import the .obj file residing in <subdirectory>, the <subdirectory> will be dublicated for the material library and cause an error, at least in the native blender import. I propose the following change that works for me in R2018a, ubuntu 18.04, blender 2.79:
(write_wobj.m:87)
if(isfield(OBJ,'material')&&~isempty(OBJ.material))
filename_mtl=fullfile(filefolder,[filename '.mtl']);
%fprintf(fid,'mtllib %s\n',filename_mtl);
% --- Added by Jerry Wang on Feb 6, 2019 ----------
filename_mtl2=[filename '.mtl'];
fprintf(fid,'mtllib %s\n',filename_mtl2);
% --- End amendment -------------------------------
write_MTL_file(filename_mtl,OBJ.material)
end
Great work! How do I get the (X,Y,Z) coordinates for this mesh?
pretty buggy, but it works for me with the changes suggested by Mike in the comments
even when I use slash or back slash same error:
OBJ=read_wobj('examples\example10.obj');
Undefined function 'read_wobj' for input arguments of type 'char'.
plz ..how to fix this error:
OBJ=read_wobj('examples/example10.obj');
Undefined function 'read_wobj' for input arguments of type 'char'.
can you tell from where we can get .obj and .mtl files.
This is not the finest example of modern coding practices. But, it sure saved me a lot of time over writing my own. Thank you, Dirk-Jan Kroon!
I came across two bugs which I addressed as follows:
ERROR 1: “invalid file identifier…”
I encapsulated the ‘readmtl’ call (near line 80) using the following:
% START OF CODE
if exist(filename_mtl,'file') == 2
material=readmtl(filename_mtl,verbose);
end
% END OF CODE
ERROR 2: "field assignment to a non-structure array object."
This error is due to the preallocation of the variable "objects." I fixed the problem by defining a 'defaultobject' and using this value you preallocate the array. Of course this defaultobject needs to be defined in every function that uses this preallocation schema.
% At lines ~50 and ~370, I added the following line:
defaultobject = struct('data',struct(),'type','');
% Then I search and replaced:
objects(no+10001).data=0
% with
objects(no+10001)=defaultobject
This works for now.
*backs away slowly*
It does not check if there is a mtl file in the first place. After fixing that myself I had a weird error about the "object" variable: error trying to assign a field in a non-struct object. Couldn't be bothered after that so I'll just write my own.
Excellent. However, I have found a bug with Di3D files that do not have a normal defined; the read file gets confused by a trailing / as in f 1271/674/
My kludgy fix is to amend the function stringsplit:
%i=find(tline(2:end-1)==tchar)+1; i_start=[1 i+1]; i_end=[i-1 length(tline)]; %as supplied
i=find(tline(2:end)==tchar)+1;
if i(end)==length(tline) % theres a 'char' at the end of the line
i = i(1:end-1); %drop last one
i_start=[1 i+1]; i_end=[i-1 length(tline)-1];
else
i_start=[1 i+1]; i_end=[i-1 length(tline)];
end
Sorry for the 1 star. Mathworks's commenting system is clearly not very polished.
In any case, code doesn't work with example .obj format provided and then example code in the function. After some fiddling, it is clear that % is being recognized as an object type, and if .obj file contains types other than those specified, the code doesn't execute well.
Works well for me but question is how to show the mesh model in Matlab?
I tried this on an obj file created by meshlab and it returned this error
% OBJ File Generated by Meshlab
%
% Object example-cloud.obj
%
% Vertices: 197749
% Faces: 0
%
??? Subscripted assignment dimension mismatch.
Error in ==> read_wobj at 90
vertices(nv,1:4)=data;
do you know how to fix it ? or how to obtain a 3d coordinates from meshlab?
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
I have the same problem as Nabil. you have found the solution? Thank you
I tried this on an obj file created by meshlab and it returned this error
% OBJ File Generated by Meshlab
%
% Object example-cloud.obj
%
% Vertices: 197749
% Faces: 0
%
??? Subscripted assignment dimension mismatch.
Error in ==> read_wobj at 90
vertices(nv,1:4)=data;
do you know how to fix it ? or how to obtain a 3d coordinates from meshlab?
thanks
mourad, check filename for correct slash orientation.
Under Linux, you should use
OBJ=read_wobj('examples/example10.obj')
instead of
OBJ=read_wobj('examples\example10.obj')
from commented example.
Rely good work but it give me that error so any one can help me cause i'm anew user for matlab
??? Error using ==> fread
Invalid file identifier. Use fopen to generate a valid file identifier.
Error in ==> read_wobj>file2cellarray at 298
file_text=fread(fid, inf, 'uint8=>char')';
Error in ==> read_wobj>readmtl at 363
file_words=file2cellarray(filename_mtl);
Error in ==> read_wobj at 78
material=readmtl(filename_mtl,verbose);
and that in read file
thanks for help
However, it is painfully slow at reading larger files.
Works well, good help text, well written.
Worked great!
So far this is a good find. I have found a bug if the file name of the obj contains a space. In line 69 of read_wobj.m: filename_mtl=fullfile(filefolder,data); returns the error:
??? Undefined function or method 'eq' for input arguments of type 'cell'.
Error in ==> fullfile at 39
elseif (f(end)==fs) || (part(1)==fs || (bIsPC && (f(end)=='/' || part(1)=='/')) )
*haidi
I know the for-loop is killing the speed in Matlab, especially because the wavefront obj. format is really broad.
If you know your data at forehand, you can remove probably more than 80% of the lines of code.
Too slow for large models!
Hi,Jan:
thanks for your code.I have a question that how can i using the texture data when show the 3D objtect? In your code ,you only used in vertices and faces. Looking forword to your answer.
it's great work! thanks