From e555119c739fb35e3bdd8905050104ae0a4692e2 Mon Sep 17 00:00:00 2001 From: Giorgio Vazzana Date: Sun, 13 Nov 2011 16:09:58 +0100 Subject: mandelbrot: correct and simplify the formula used in NORMALIZED_ITERATION_COUNT Use log(sqrt(mb->bailout)) instead of log(mb->bailout) because mb->bailout represent the bailout radius squared, and then simplify the two sqrt(). This is also slightly faster. Signed-off-by: Michael Niedermayer --- libavfilter/vsrc_mandelbrot.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'libavfilter') diff --git a/libavfilter/vsrc_mandelbrot.c b/libavfilter/vsrc_mandelbrot.c index 719e169928..7a1a864fef 100644 --- a/libavfilter/vsrc_mandelbrot.c +++ b/libavfilter/vsrc_mandelbrot.c @@ -185,7 +185,7 @@ static void draw_mandelbrot(AVFilterContext *ctx, uint32_t *color, int linesize, if(zr*zr + zi*zi > mb->bailout){ switch(mb->outer){ case ITERATION_COUNT: zr= i; break; - case NORMALIZED_ITERATION_COUNT: zr= i + (log(log(mb->bailout)) - log(log(sqrt(zr*zr + zi*zi))))/log(2); break; + case NORMALIZED_ITERATION_COUNT: zr= i + log2(log(mb->bailout) / log(zr*zr + zi*zi)); break; } c= lrintf((sin(zr)+1)*127) + lrintf((sin(zr/1.234)+1)*127)*256*256 + lrintf((sin(zr/100)+1)*127)*256; break; @@ -200,7 +200,7 @@ static void draw_mandelbrot(AVFilterContext *ctx, uint32_t *color, int linesize, if(t*t + zi*zi > mb->bailout){ switch(mb->outer){ case ITERATION_COUNT: zr= i; break; - case NORMALIZED_ITERATION_COUNT: zr= i + (log(log(mb->bailout)) - log(log(sqrt(t*t + zi*zi))))/log(2); break; + case NORMALIZED_ITERATION_COUNT: zr= i + log2(log(mb->bailout) / log(t*t + zi*zi)); break; } c= lrintf((sin(zr)+1)*127) + lrintf((sin(zr/1.234)+1)*127)*256*256 + lrintf((sin(zr/100)+1)*127)*256; break; -- cgit v1.2.3