十進BASIC 第2掲示板 過去ログ

!経線と緯線と使って、球体をワイヤーフレームで描画する

SET WINDOW -2,2,-2,2

FOR t=0 TO 90 STEP 15 !角度を等分割する
   LET a=SIN(RAD(t)) !端付近：密、中央付近：疎
   LET b=1
   FOR i=0 TO 360 !経線　※楕円を描く
      LET x=a*COS(RAD(i))
      LET y=b*SIN(RAD(i))
      PLOT LINES: x,y;
   NEXT i
   PLOT LINES
NEXT t

FOR i=-180 TO 180 STEP 10 !緯線　※水平線を描く
   LET y=SIN(RAD(i)) !角度を等分割する
   LET x=SQR(1-y^2) !極付近：密、０度付近：疎
   PLOT LINES: -x,y; x,y
NEXT i
PLOT LINES

END

!楕円を重ねると球体に見える！？

SET WINDOW -2,2,-2,2

LET b=1
FOR a=0 TO 1 STEP 0.25

   FOR i=0 TO 360 !楕円を描く
      LET x=a*COS(RAD(i))
      LET y=b*SIN(RAD(i))
      PLOT LINES: x,y;
   NEXT i
   PLOT LINES

NEXT a

LET a=1
FOR b=0 TO 1 STEP 0.25

   FOR i=0 TO 360 !楕円を描く
      LET x=a*COS(RAD(i))
      LET y=b*SIN(RAD(i))
      PLOT LINES: x,y;
   NEXT i
   PLOT LINES

NEXT b

END

!ワイヤーフレームで曲面を描く　SAMPLE\3DPLOT.BASを改修。

SUB rotx(x,y,z,a)
   LET y0=y*cos(a)-z*sin(a)
   LET z0=y*sin(a)+z*cos(a)
   LET y=y0
   LET z=z0
END SUB
SUB roty(x,y,z,a)
   LET x0=x*cos(a)+z*sin(a)
   LET z0=-x*sin(a)+z*cos(a)
   LET x=x0
   LET z=z0
END SUB
SUB rotz(x,y,z,a)
   LET x0=x*cos(a)-y*sin(a)
   LET y0=x*sin(a)+y*cos(a)
   LET x=x0
   LET y=y0
END SUB
SUB convert(x,y,z)
   CALL rotz(x,y,z,RAD(-30))
   CALL rotx(x,y,z,RAD(-70))
END SUB
SUB plotTo(x,y,z)
   LET x1=x
   LET y1=y
   LET z1=z
   CALL convert(x1,y1,z1)
   PLOT LINES:x1,y1;
END SUB
SUB PenUp
   PLOT LINES
END SUB
SUB PlotText(x,y,z,s$)
   CALL convert(x,y,z)
   PLOT TEXT ,AT x,y: s$
END SUB

!媒体変数表示
DEF fx(u,v)=COS(u)*SIN(v) !球　u=[0,2*PI],v=[0,PI]　※球座標(r,θ,φ)
DEF fy(u,v)=SIN(u)*SIN(v)
DEF fz(u,v)=COS(v)

SET WINDOW -2,2,-2,2

FOR f=0 TO 360 !フレーム・アニメーション
   SET DRAW mode hidden !ちらつき防止（開始）
   CLEAR

   ! 軸を描く
   CALL PlotTo(0,0,0)
   CALL PlotTo(2,0,0)
   CALL PlotTo(0,0,0)
   CALL PlotTo(0,2,0)
   CALL PlotTo(0,0,0)
   CALL PlotTo(0,0,2)
   CALL PenUp
   CALL PlotText(2,0,0,"x")
   CALL PlotText(0,2,0,"y")
   CALL PlotText(0,0,2,"z")

   ! 曲面を描く
   FOR u=0 TO 360 STEP 15
      FOR v=0 TO 180 STEP 15
         LET x=fx(RAD(u),RAD(v))
         LET y=fy(RAD(u),RAD(v))
         LET z=fz(RAD(u),RAD(v))
         CALL rotx(x,y,z,RAD(f))
         CALL PlotTo(x,y,z)
      NEXT v
      CALL PenUp
   NEXT u
   FOR v=0 TO 180 STEP 30
      FOR u=-1 TO 360 STEP 30
         LET x=fx(RAD(u),RAD(v))
         LET y=fy(RAD(u),RAD(v))
         LET z=fz(RAD(u),RAD(v))
         CALL rotx(x,y,z,RAD(f))
         CALL PlotTo(x,y,z)
      NEXT u
      call PenUp
   NEXT v

   SET DRAW mode explicit !ちらつき防止（終了）
   !WAIT DELAY 0.1
NEXT f

END