demoloadawobj.m

%% An introduction to loadawobj
% Some examples of usage of loadawobs.m and companion files
% loadawmtl.m drawaw.m
%
% This file can be `published' with publish('demoloadawobj','pdf')
%% Simple files
% loadawobj, at its simplest, will load a file and draws it on the
% current figure,
% e.g. loadawobj('icosahedron.obj').
%
% But more control is possible by extracting the vertices and faces
% information from the file
%
% *note*
%
% # Since the icosahedron only has triangles, only F3 needs to be in the output list,
% # the transpose of the vertices and faces matrix is given to the patch command.
fig=figure; % open a new figure
modelname='icosahedron.obj';
[v,F3]=loadawobj('icosahedron.obj');
patch('Vertices',v','Faces',F3','FaceColor','g');
view(30,0);
axis('equal');
snapnow
pause(1)
%% line drawings
clf
loadawobj('obj/diamond.obj');
view(-7,26);
title('diamond only has vertices and lines');
snapnow
pause(1)

%% S=loadawobj('file.obj')
% If there is a single output variable, loadawobj will return a
% structure with more details extracted from the obj file.
%
% *The structure fields are*
%
%  version
%  v : vertices
%  f3,f4,f5,f6 : A list of faces with 3,4,5, and 6 vertices.
%  g : Group names
%  g3 g4 : The index indicates the group by faces
%  l : Lines (see diamond.obj)
%  umat3 umat4 : The index indicates to which group a face belongs
%  mtllib : The material library (load with loadawmtl)
%  usemtl : Material names
%  vt : Vertex textures
%  vn : Vertex normals
%  tc3 : texture coorndate for 3 face polygons
%  tc4 : texture coorndate for 4 face polygons
%  vn3 : texture coorndate for 3 face polygons
%  vn4 : texture coorndate for 4 face polygons
%
% *Note*
%
% g3 and g4 are the same length as f3 and f4 and indicate to which group a
% face set belongs.
%
% Only 3-6 faces are currently supported, it should be relatively easy
% to add more


%% plane.obj 
% Load and display a biplane
% Check the contents of drawaw for more details on how to handle
% Matlab(R)'s FaceVertexColorData 
clf
modelname='obj/plane.obj';
S=loadawobj(modelname);
if isfield(S,'mtllib') 
    mtl=loadawmtl(['obj/' S.mtllib]);
end
drawaw(S,mtl)
view(-24,36);
light
snapnow;
pause(1)
% 
%% functions for coordinate transforms
%
% these can be used in place,
% i.e. S.v=tfverts(Rz180*Rx90,[10;0;0],S.v)
Rz=@(th)[cos(th) -sin(th) 0;sin(th) cos(th) 0; 0 0 1];
Rx=@(th)[1 0 0;0 cos(th) -sin(th);0 sin(th) cos(th)];
Ry=@(th)[cos(th) 0 sin(th);0 1 0;-sin(th) 0 cos(th)];
tfverts=@(R,p,v) R*v+p*ones(1,length(v));
%%
% so in-order to avoid looking at the back end of a cow we can
% rotate it around the y axis by 160 degrees
modelname='obj/cow.obj';
S=loadawobj(modelname);
S.v=tfverts(Ry(160*pi/180),[0 0 0]',S.v);
if isfield(S,'mtllib') 
    mtl=loadawmtl(['obj/' S.mtllib]);
end
clf;drawaw(S,mtl)
camlight
snapnow
pause(1)
close(fig)