with(plots):
a,b,c:=0.5,0.5,1: Rs:=1:#1.7:
eqSphere:=(x-a)^2+(y-b)^2+(z-c)^2-Rs^2: 
sphpara:=(u,v) -> expand([a,b,c]+Rs*[sin(v)*cos(u),sin(v)*sin(u),cos(v)]):
Rcyl:=0.5: 
eqcyl:=x^2+y^2-Rcyl^2: eqcone:=x^2+y^2-z^2:
                   
p:=3: g:=80:
#===== différence cone moins sphère =======
#min(min(eqSphere),min(eqcone)) ou  min(eqSphere,op(eqcone)) ou  max(-eqSphere,-eqcone) ou  min(eqSphere,eqcone)
display( [implicitplot3d( min(eqSphere,-eqcone),x=-p..p,y=-p..p,z=-p/4..2*p,grid=[g,g,g],style=patchnogrid,color=cyan)
         ,plot3d(sphpara(u,v),u=0..2*Pi,v=0..Pi,style=line,thickness=1)
          ],scaling=constrained,axes=none,orientation=[-140,70,170], view=[-p/2..p,-p/2..p,-p/2..p]) ;

#===== intersection cone - sphère =======
## max(-eqcone,eqSphere) ou min(-eqSphere,eqcone) ou  min(-eqSphere,op(eqcone)) ou max(eqSphere,-op(eqcone)) 
p:=3: g:=100:
display( [implicitplot3d( min(eqSphere,eqcone),x=-p..p,y=-p..p,z=-p/4..2*p,grid=[g,g,g],style=patchnogrid,color=cyan)
         ,plot3d(sphpara(u,v),u=0..2*Pi,v=0..Pi,style=line,thickness=1)      
         ],scaling=constrained,axes=none,orientation=[-140,70,170], view=[-p/2..p,-p/2..p,-p/2..2*Rs]);  


#===== différence sphère moins dodéca =======
p:=2:
## min(-min(eqSphere),-min(eqcone)) ou max(min(eqSphere),min(eqcone))
display( [implicitplot3d(min(-eqSphere,eqcone),x=0 .. 2*p,y=0 ..2*p,z=0 .. 2*p,grid=[g,g,g],style=patchnogrid,color=cyan)
        ,plot3d(sphpara(u,v),u=0..2*Pi,v=0..Pi,style=line,thickness=1) 
         ],scaling=constrained,axes=none, view=[-p/2..p,-p/2..p,-p/2..2*Rs]);


#===== réunion sphère-dodéca =======
p:=1.5:
eqSphere:=(x-0.5)^2+(y-0.5)^2+(z-0.5)^2-R^2:
## min( eqSphere,eqcone)ou max(-eqSphere,-eqcone)
display( [implicitplot3d(min(eqSphere,eqcone), x=-p .. p,y=-p .. p,z=-p .. p,grid=[g,g,g],style=patchnogrid,color=cyan)
          ],scaling=constrained,axes=none,orientation=[70,70,2]);


#=====sections planes d'un objet =======
p:=1.5:
eqSphere:=(x)^2+(y)^2+(z)^2-Rs^2:
eps:=1:
plan1:=eps+x-y-z: plan2:=eps+x+y+z: 
display( [implicitplot3d(min(-eqSphere,plan1,plan2), x=-p .. p,y=-p .. p,z=-p .. p,grid=[g,g,g],style=patchnogrid,color=cyan)
          ],scaling=constrained,axes=none,orientation=[-90,45,30]);