# 3D graphics bug?

Hi,

When I use the following code and I change the values of phi or theta, the previous red dot(point of projection) remains on the image and the new dot is added onto the image, giving two red dots. If I repeatedly change the values then more red dots appear. This problem does not occur if I get rid of the polygon inside the sphere. I'm not sure why this is happening...

Works:

```
S = sphere(size=10,color="yellow",opacity=0.5)
north_pole = point3d((0,0,10), color="blue")
r = 10
@interact
def _(theta = slider(0,2*pi,pi/20, default = pi/3, label="theta"),
phi = slider(0,2*pi,pi/20, default = pi/4, label="phi")):
point_of_projection = point3d((r*sin(theta)*cos(phi),r*sin(theta)*sin(phi),r*cos(theta)), color="red")
show(S + north_pole + point_of_projection)
```

Doesn't work:

```
Z = Polyhedron([[2,3,3],[3,0,3],[2,6,1],[1,0,1],[6,7,2]])
Z_set_as_graphics = Z.show()
S = sphere(size=10,color="yellow",opacity=0.5)
north_pole = point3d((0,0,10), color="blue")
r = 10
@interact
def _(theta = slider(0,2*pi,pi/20, default = pi/3, label="theta"), phi = slider(0,2*pi,pi/20, default = pi/4, label="phi")):
point_of_projection = point3d((r*sin(theta)*cos(phi),r*sin(theta)*sin(phi),r*cos(theta)), color="red")
show(Z_set_as_graphics + S + north_pole + point_of_projection)
```

I just tried this, and don't get this behavior... maybe because you posted the version of the code without the polygon?

sorry! here's the code:

Z = Polyhedron([[2,3,3],[3,0,3],[2,6,1],[1,0,1],[6,7,2]]) Z_set_as_graphics = Z.show() S = sphere(size=10,color="yellow",opacity=0.5) north_pole = point3d((0,0,10), color="blue") r = 10 @interact def _(theta = slider(0,2*pi,pi/20, default = pi/3, label="theta"), phi = slider(0,2*pi,pi/20, default = pi/4, label="phi")): point_of_projection = point3d((r*sin(theta)*cos(phi),r*sin(theta)*sin(phi),r*cos(theta)), color="red") show(Z_set_as_graphics + S + north_pole + point_of_projection)

Ok, I pasted that above for clarity.

I see it now. Like sunspots...