[pstricks] psarc

Poul Riis Poul.Riis at skolekom.dk
Sat Nov 22 13:04:24 CET 2008

Still one problem remains in my figure below: How can I reverse the
direction of the arrow in case w0y is positive?

Poul Riis


	/gg 9.82 def
	/v0 20 def
	/w0y 10 neg def
	/theta 60 def
	/v0x v0 theta cos mul def
	/v0z v0 theta sin mul def
	/wang 1 v0x div 60 mul def
	/alpha 0.6 def
	/eps 0.9 def
	/epsz 0.8 def
	/beta eps 1 add alpha 1 add div def
	/alphabeta alpha beta mul def
	/enminusalphabeta 1 alphabeta sub def
	/enminusbeta 1 beta sub def
	/x0 0 def
	/z0 0 def
	/xT v0z v0x mul gg div x0 add def
	/zT v0z dup mul 2 div gg div z0 add def
	/pi 3.141592 def
\uput{2mm}[0](!50 16){$v_0_x=$\psPrintValue[valuewidth=6,fontscale=8]{v0x}}
\uput{2mm}[0](!50 14){$w_0_y=$\psPrintValue[valuewidth=6,fontscale=8]{w0y}}
\multido{\nn=0+1}{6}{%\uput{2mm}[0](!10 2 2 \nn\space mul add
\parabola[linecolor=Blue1](!x0 z0)(!xT x0 add zT)%
\parabola[arrowscale=2,arrows=->,linecolor=Blue1,linewidth=0.25pt](!x0 xT
2 div add zT 3 mul 4 div)(!xT x0 add zT)%
\pscircle*[linecolor=red](!xT x0 add zT){0.5}
\psarc[linecolor=black,linewidth=0.4pt]{->}(!xT x0 add zT){1.5}{!90 w0y
abs wang mul sub}{!90 w0y abs wang mul add}
\pstVerb{v0z epsz mul /v0z exch def
 v0x enminusalphabeta mul w0y alphabeta mul add /v1x exch def
 w0y enminusbeta mul v0x beta mul add /w0y exch def
 v1x /v0x exch def
 xT 2 mul x0 add /x0 exch def
 v0z v0x mul gg div /xT exch def
 v0z dup mul 2 div gg div z0 add /zT exch def }%


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