$GRAB的用法是怎樣的？我看了例子還是不明白，請大蝦解釋一下下面的例子，$GRAB的那幾個參數(shù)到底是什么意思呢？謝謝~ kc2 8Q2  
H)rJ>L  
^}<]sjmk  
SYSTEM NEW Ij9=J1c4  
RESET FR\r/+n:t0  
@[Wf!8_  
EMITTING DISK Z 0 1 1 1000 c57`mOe/b  
d-gcXaA-8  
STATS POSITION zv^+8h7k  
.73sY5hdTN  
?gjkgCbC#  
$GRAB 'Centroid:' 0 1  XCENT YCENT ZCENT fS%B/h=  
_6]tbni?v  
$REG XCENT YCENT ZCENT  8SCXA9}  
%PPkT]~\  
RETURN

我今天也碰到了相同的問題，我是這麼認為的： ),0Ea~LB4  
先看運行命令後的提示： ak(P<OC-  
--- SYSTEM NEW i.+#a2   
--- RESET 3 FLht L  
--- EMITTING DISK Z 0 1 1 1000 ;zi4W1  
Total flux in rays created by this emitter is 1.000000 WQHlf0]  
--- STATS POSITION &-|(q!jm  
Current Statistics for Object 0 -
+VHoYEW  
Total Flux = 1.00000 from 1000 rays (100.00%) }k6gO0z  
X Y Z _i0,?U2C  
Centroid:                  0.110887E-01      0.479158E-01        0.00000 </qli-fXB}  
RMS Deviation:        0.485753              0.510739                0.00000 1@Rl^ey  
Maximum Spread:  -.997810                -1.02958                  0.00000 ]ov"&,J  
                              to 0.976937              0.945055                  0.00000 n^rzl6dy  
--- $GRAB 'Centroid:' 0 1 XCENT YCENT ZCENT S&~;l/  
--- $REG XCENT YCENT ZCENT 7XiR)jYo*  
Z~: XCENT 1.10887E-2 G88g@Exk  
Y~: YCENT 4.79158E-2 AO0aOX8_+D  
X~: ZCENT 0 =bb