[pstricks] error using postscript in coordinates?

[Zbigniew Nitecki]

I don't understand my error below.  I am trying to draw a hemisphere  
with a cone cut out.

*******************
	\begin{pspicture}(-2,-2)(2,2)
		\pstThreeDCoor[xMin=0, xMax=2, yMin=0, yMax=2, zMin=0, zMax=2]
		
		\multido{\rt=0+20}{18}{
			\pstThreeDLine(0,0,0)(\rt\space cos 0.707 mul,\rt\space sin 0.707  
mul,0.707)
			\parametricplotThreeD(0,45){%
				t cos \rt\space cos mul
				t cos \rt\space sin mul
				t sin%
				}
			}
			
		\multido{\rz=0.007+0.1}{7}{
			\pstThreeDEllipse(0,0,\rz)(\rz,0,0)(0,\rz,0)
%			\pstThreeDEllipse(0,0,\rz)(1 \rz \rz mul sub 0.5 exp,0,0)(0,1 \rz  
\rz mul sub 0.5 exp,0)%
		}
	\end{pspicture}
*****************************
With the last line commented out (as above) I get a picture, whereas  
when it is uncommented I get an error:
Error: /undefined in 0.0070.007mul
Operand stack:
    1
Execution stack:
    %interp_exit   .runexec2   --nostringval--   --nostringval--   -- 
nostringval--   2   %stopped_push   --nostringval--   -- 
nostringval--   --nostringval--   false   1   %stopped_push   1905    
1   3   %oparray_pop   1904   1   3   %oparray_pop   1888   1   3    
%oparray_pop   1771   1   3   %oparray_pop   --nostringval--    
%errorexec_pop   .runexec2   --nostringval--   --nostringval--   -- 
nostringval--   2   %stopped_push   --nostringval--
Dictionary stack:
    --dict:1148/1684(ro)(G)--   --dict:0/20(G)--   --dict: 
115/200(L)--   --dict:176/300(L)--   --dict:38/200(L)--   --dict:110/200(L)--
Current allocation mode is local
Last OS error: 2
Current file position is 246041
GPL Ghostscript 8.63: Unrecoverable error, exit code 1
### FAILED to generate /tmp/altpdflatex.4856-1258045945/ 
MinimalPST3DTest.pdf ()

Zbigniew Nitecki
Department of Mathematics
Tufts University
Medford, MA 02155

telephones:
Office    (617)627-3843
Dept.    (617)627-3234
Dept. fax    (617)627-3966
http://www.tufts.edu/~znitecki/

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