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% D. Roegel, 7 January 2001
% roegel@loria.fr
verbatimtex
%&latex
\documentclass{article}
\usepackage{mathpple}
\begin{document}
etex
input 3danim
input 3dgeom
output_res:=72;
drawing_scale:=10cm;
numeric lsa,lsb,lsc,aasc,aasb,absc;
lsa=9;lsb=8;lsc=4;aasc=60;aasb=40;absc=30;
vardef def_T(expr inst)=
new_obj_points(inst,4); % 4 points
set_T_points(inst);
enddef;
vardef set_T_points(expr inst)=
save hp,kp,sa,sc,inter;new_point(h);new_point(k);
set_point(1)(0,0,0); % S
set_point(2)(lsa,0,0); % A
set_point(4)(lsc*cosd(aasc),lsc*sind(aasc),0); % C
vec_diff_(h,pnt(2),pnt(1));
vec_unit_(h,h);vec_mult_(h,h,lsb*cosd(aasb));
vec_sum_(h,h,pnt(1));
vec_diff_(k,pnt(4),pnt(1));
vec_unit_(k,k);vec_mult_(k,k,lsb*cosd(absc));
vec_sum_(k,k,pnt(1));
new_plane(hp)(1,1,1);
new_plane(kp)(1,1,1);
new_line(sa)(1,2);
new_line(sc)(1,4);
new_line(inter)(1,1);
def_orth_pl_l_p_(hp)(sa)(h);
def_orth_pl_l_p_(kp)(sc)(k);
if def_inter_l_pl_pl(inter)(hp)(kp): % there is an intersection
if def_point_at(3,-lsb,1)(inter):
else:
message "PROBLEM";
fi;
else:
message "PROBLEM";
set_point(3)(1,1,1);
fi;
free_line(inter);free_line(sc);free_line(sa);
free_plane(kp);free_plane(hp);
free_point(k);free_point(h);
enddef;
vardef draw_T(expr inst)=
draw_line(1,2);draw_line(1,4);draw_line(1,3);
draw_line(2,3);draw_line(3,4);
drawoptions(dashed evenly);
draw_line(2,4);
drawoptions();
label_obj.bot(btex $S$ etex,1);
label_obj.rt(btex $A$ etex,2);
label_obj.top(btex $B$ etex,3);
label_obj.lft(btex $C$ etex,4);
enddef;
assign_obj("tetra","T");
%for i:=0 upto 20:
i=0;
beginfig(100+i);
% Observator
set_point_(Obs)(20*cosd(3.6*i-150),20*sind(3.6*i-150),6);
Obs_phi:=90;Obs_dist:=2;point_of_view_obj("tetra",1,Obs_phi);
draw_obj("tetra");
endfig;
%endfor;
end.
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