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mandel.h File Reference

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Functions
int	mandel_color (double x, double y)
void	mandel_set ()

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Function Documentation

int mandel_color (  double  x, double  y )

File ......... mandel.cpp Published .... 2005-02-07 Author ....... grymse@alhem.net Definition at line 29 of file mandel.cpp. References STOPLIM. Referenced by Grid::GetXY(). { double cx,cy; double limit; double ax,ay; double a1,b1; double lp; double a2,b2; cx = -0.3 + Globals::m_zx; cy = -0.66 + Globals::m_zy; // Globals::m_scale = 0.002; limit = 4; // {What is the * mathematical * value of this point?} ax = cx + (x) * Globals::m_scale; ay = cy + (y) * Globals::m_scale; // {And now for the magic formula!} a1 = ax; b1 = ay; lp = 0; #define STOPLIM 40 do { // {Do one iteration.} lp = lp + 1; a2 = a1 * a1 - b1 * b1 + ax; b2 = 2 * a1 * b1 + ay; // {This is indeed the square of a + b1, done component-wise.} a1 = a2; b1 = b2; } while (!(lp > STOPLIM || ((a1 * a1) + (b1 * b1) > limit))); // {The first condition is satisfied if we have convergence. // The second is satisfied if we have divergence.} // {Define colour and draw pixel.} if (lp > STOPLIM) { lp = STOPLIM; } // {If the point converges, it is part of the brot and we // draw it with colour 0, or black.} // pixel(x + 160,y + 100,lp); return (int)lp; }

void mandel_set (   )

Definition at line 77 of file mandel.cpp. { double x,y; double cx,cy; double limit; double ax,ay; double a1,b1; double lp; double a2,b2; // {Set up initial values for drawing. Try compiling the program // with different values here if you like!} cx = 0; cy = 0; // Globals::m_scale = 0.02; limit = 4; // {Loop through all pixels on screen. For reasons that will become // clear, I am counting not from (0,0) but from (-160,-100).} for (x = -160; x < 160; x++) { for (y = -100; y <= 100; y++) { // {What is the * mathematical * value of this point?} ax = cx + x * Globals::m_scale; ay = cy + y * Globals::m_scale; // {And now for the magic formula!} a1 = ax; b1 = ay; lp = 0; do { // {Do one iteration.} lp = lp + 1; a2 = a1 * a1 - b1 * b1 + ax; b2 = 2 * a1 * b1 + ay; // {This is indeed the square of a + bi, done component-wise.} a1 = a2; b1 = b2; } while (lp > 255 || ((a1 * a1) + (b1 * b1) > limit)); // {The first condition is satisfied if we have convergence. // The second is satisfied if we have divergence.} // {Define colour and draw pixel.} if (lp > 255) { lp = 0; } // {If the point converges, it is part of the brot and we // draw it with colour 0, or black.} // pixel(x + 160,y + 100,lp); } } // for (x) }

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