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// obj.cmd
// Surface Evolver script for creating Wavefront OBJ format 3D graphics file.
// Result file requires EvolverOBJcolors.mtl file in same directory.
// File format reference: http://www.martinreddy.net/gfx/3d/OBJ.spec
// Edges are shown as 4-sided tubes. The relative tube diameter
// can be adjusted where actual_tube_radius is set below.
/* Usage:
Set which edges and facets you want to show with the
"show edge where ..." and "show facet where ..." commands.
Set obj_double_sided to 1 if you want back sides of facets.
Set obj_edge_flag to 0 if you want no edges shown.
Run obj and redirect output to file, for example
obj >>> "filename.obj"
*/
define vertex attribute obj_vnum integer
obj_double_sided := 0 // set to 1 to do front and back facets
obj_edge_flag := 1 // set to 1 to do small tubes around shown edges
// or 0 to do edges as lines
obj_tube_radius := 0.002; // relative size of edge tubes.
obj_edge_tubes := {
local tube_sides,t_angle,actual_tube_radius;
local ax,ay,az,bx,by,bz,mag,inx,cinx;
// Doing edges one by one, using negative relative vertex indexing, so
// vertices can be listed with the tube faces.
tube_sides := 4;
t_angle := 2*pi/tube_sides;
actual_tube_radius := obj_tube_radius*sqrt(max(vertex,x^2+y^2+z^2));
for ( cinx := 0 ; cinx <= 15 ; cinx += 1 )
{ printf "usemtl color%d\n",cinx;
foreach edge ee where color == cinx and show do
{
// find two orthogonal directions to edge; if possible,
// one along adjacent facet
if ee.valence > 0 then
{ ax := ee.facet[1].x;
ay := ee.facet[1].y;
az := ee.facet[1].z;
}
else
{ if abs(ee.x) < abs(ee.y) and abs(ee.x) < abs(ee.z) then
{ ax := 1; ay := 0; az := 0;}
else if abs(ee.y) < abs(ee.z) then
{ ax := 0; ay := 1; az := 0; }
else
{ ax := 0; ay := 0; az := 1; };
};
bx := ay*ee.z - az*ee.y;
by := az*ee.x - ax*ee.z;
bz := ax*ee.y - ay*ee.x;
ax := by*ee.z - bz*ee.y;
ay := bz*ee.x - bx*ee.z;
az := bx*ee.y - by*ee.x;
// normalize to radius
mag := sqrt(ax^2+ay^2+az^2);
if mag <= 0 then continue;
ax *= actual_tube_radius/mag;
ay *= actual_tube_radius/mag;
az *= actual_tube_radius/mag;
mag := sqrt(bx^2+by^2+bz^2);
if mag <= 0 then continue;
bx *= actual_tube_radius/mag;
by *= actual_tube_radius/mag;
bz *= actual_tube_radius/mag;
for ( inx := 0 ; inx < tube_sides ; inx += 1 )
{
printf "v %f %f %f\n",ee.vertex[1].x+ax*cos(inx*t_angle)+bx*sin(inx*t_angle),
ee.vertex[1].y+ay*cos(inx*t_angle)+by*sin(inx*t_angle),
ee.vertex[1].z+az*cos(inx*t_angle)+bz*sin(inx*t_angle);
printf "v %f %f %f\n",ee.vertex[1].x+ee.x+ax*cos(inx*t_angle)+bx*sin(inx*t_angle),
ee.vertex[1].y+ee.y+ay*cos(inx*t_angle)+by*sin(inx*t_angle),
ee.vertex[1].z+ee.z+az*cos(inx*t_angle)+bz*sin(inx*t_angle);
};
/* quads should work, but Meshlab interprets them as single triangles!
printf "f -6 -5 -7 -8\n";
printf "f -4 -3 -5 -6\n";
printf "f -2 -1 -3 -4\n";
printf "f -8 -7 -1 -2\n";
*/
printf "f -6 -5 -7\n";
printf "f -6 -7 -8\n";
printf "f -4 -3 -5\n";
printf "f -4 -5 -6\n";
printf "f -2 -1 -3\n";
printf "f -2 -3 -4\n";
printf "f -8 -7 -1\n";
printf "f -8 -1 -2\n";
}
}
} // end obj_edge_tubes
// Edges as lines
obj_edge_lines := {
local cinx;
for ( cinx := 0 ; cinx <= 15 ; cinx += 1 )
{ printf "usemtl color%d\n",cinx;
foreach edge ee where color == cinx and show do
{
printf "l %d %d\n",ee.vertex[1].obj_vnum,
ee.vertex[2].obj_vnum;
}
}
} // end obj_edge_lines
obj := {
local vnumber,cinx;
if rgb_colors then
{ errprintf "obj error: obj script does not do RGB colors; do rgb_colors off.\n";
abort;
};
if torus then
{ errprintf "Cannot run 'obj' command in torus mode. Do 'detorus' first.\n";
abort;
};
if symmetry_group then
{ errprintf "Cannot run 'obj' command in symmetry group mode. Do 'detorus' first.\n";
abort;
};
if space_dimension != 3 then
{ errprintf "The 'obj' command must be run in three-dimensional space.\n";
abort;
};
if surface_dimension == 1 then
{ errprintf "The 'obj' command is not meant for the string model.\n";
abort;
};
if simplex_representation then
{ errprintf "The 'obj' command is not meant for the simplex model.\n";
abort;
};
if lagrange_order >= 2 then
{ errprintf "The 'obj' command is meant for the linear model, not quadratic or Lagrange.\n";
abort;
};
printf "# OBJ version of %s \n",datafilename;
printf "# Produced by Surface Evolver with obj.cmd script\n\n";
printf "mtllib EvolverOBJcolors.mtl\n\n";
vnumber := 0;
foreach vertex vv do
{ printf "v %f %f %f\n",vv.x,vv.y,vv.z;
vnumber += 1;
vv.obj_vnum := vnumber;
};
for ( cinx := 0 ; cinx <= 15 ; cinx += 1 )
{ printf "usemtl color%d\n",cinx;
foreach facet ff where show and frontcolor == cinx do
printf "f %d %d %d\n",ff.vertex[1].obj_vnum,
ff.vertex[2].obj_vnum,ff.vertex[3].obj_vnum;
if obj_double_sided then
foreach facet ff where show and backcolor == cinx do
printf "f %d %d %d\n",ff.vertex[1].obj_vnum,
ff.vertex[3].obj_vnum,ff.vertex[2].obj_vnum;
};
if obj_edge_flag then
obj_edge_tubes
else
obj_edge_lines;
} // end obj
/* Usage:
Set which edges and facets you want to show with the
"show edge where ..." and "show facet where ..." commands.
Set obj_double_sided to 1 if you want back sides of facets.
Set obj_edge_flag to 0 if you want no edges shown.
Run obj and redirect output to file, for example
obj >>> "filename.obj"
*/
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