Data commit

Task/Draw-a-rotating-cube/XPL0/draw-a-rotating-cube.xpl0

@@ -0,0 +1,29 @@
+def  Size=100., Speed=0.05;             \drawing size and rotation speed
+real X, Y, Z, Farthest;                 \arrays: 3D coordinates of vertices
+int  I, J, K, ZI, Edge;
+def  R2=sqrt(2.), R3=sqrt(3.), R13=sqrt(1./3.), R23=sqrt(2./3.), R232=R23*2.;
+\vertex:0       1       2       3       4       5       6       7
+[X:= [  0.,     R2,     0.,    -R2,     0.,     R2,     0.,    -R2];
+ Y:= [ -R3,    -R13,    R13,   -R13,   -R13,    R13,    R3,     R13];
+ Z:= [  0.,    -R23,   -R232,  -R23,    R232,   R23,    0.,     R23];
+Edge:= [0,1, 1,2, 2,3, 3,0, 4,5, 5,6, 6,7, 7,4, 0,4, 1,5, 2,6, 3,7];
+SetVid($101);                           \set 640x480x8 graphics
+repeat  Farthest:= 0.0;                 \find the farthest vertex
+        for I:= 0 to 8-1 do
+            if Z(I) > Farthest then [Farthest:= Z(I);  ZI:= I];
+        Clear;                          \erase screen
+        for I:= 0 to 2*12-1 do          \for all the vertices...
+            [J:= Edge(I);  I:= I+1;     \get vertex numbers for edge
+            Move(Fix(X(J)*Size)+640/2, Fix(Y(J)*Size)+480/2);
+            K:= Edge(I);
+            Line(Fix(X(K)*Size)+640/2, Fix(Y(K)*Size)+480/2,
+                if J=ZI ! K=ZI then $F001 \dashed blue\ else $0C \red\);
+            ];
+        DelayUS(55000);
+        for I:= 0 to 8-1 do
+            [X(I):= X(I) + Z(I)*Speed;  \rotate vertices about Y axis
+             Z(I):= Z(I) - X(I)*Speed;  \ (which rotates in X-Z plane)
+            ];
+until KeyHit;                           \run until a key is struck
+SetVid(3);                              \restore normal text mode
+]