Bitmap/Bézier curves/Cubic: Difference between revisions

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@@ Line 1,009: / Line 1,009: @@
 [[File:CubicXPL0.png|right]]
 <lang XPL0>include c:\cxpl\codes;          \intrinsic 'code' declarations
-func real Power(X, Y);          \X raised to the Y power; (X > 0.0)
-real    X, Y;
-return Exp(Y * Ln(X));
 proc Bezier(P0, P1, P2, P3);    \Draw cubic Bezier curve
@@ Line 1,017: / Line 1,014: @@
 def  Segments = 8;
 int  I;
-real T, A, B, C, D, X, Y;
+real S1, T, T2, T3, U, U2, U3, B, C, X, Y;
 [Move(fix(P0(0)), fix(P0(1)));
+S1:= 1./float(Segments);
+T:= 0.;
 for I:= 1 to Segments-1 do
-        [T:= float(I)/float(Segments);
+        [T:= T+S1;
-        A:= Power((1.-T), 3.);
+        T2:= T*T;
-        B:= 3.*T*Power((1.-T), 2.);
+        T3:= T2*T;
-        C:= 3.*Power(T, 2.)*(1.-T);
+        U:= 1.-T;
-        D:= Power(T, 3.);
+        U2:= U*U;
-        X:= A*P0(0) + B*P1(0) + C*P2(0) + D*P3(0);
+        U3:= U2*U;
-        Y:= A*P0(1) + B*P1(1) + C*P2(1) + D*P3(1);
+        B:= 3.*T*U2;
+        C:= 3.*T2*U;
+        X:= U3*P0(0) + B*P1(0) + C*P2(0) + T3*P3(0);
+        Y:= U3*P0(1) + B*P1(1) + C*P2(1) + T3*P3(1);
         Line(fix(X), fix(Y), $00FFFF);          \cyan line segments
         ];