diff options
| -rw-r--r-- | src/blitter/base.cpp | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/src/blitter/base.cpp b/src/blitter/base.cpp index 312ec1025..d8e33cede 100644 --- a/src/blitter/base.cpp +++ b/src/blitter/base.cpp @@ -50,8 +50,19 @@ void Blitter::DrawLine(void *video, int x, int y, int x2, int y2, int screen_wid int frac_diff = width * max(dx, dy); if (width > 1) { + /* compute frac_diff = width * sqrt(dx*dx + dy*dy) + * Start interval: + * max(dx, dy) <= sqrt(dx*dx + dy*dy) <= sqrt(2) * max(dx, dy) <= 3/2 * max(dx, dy) */ int frac_sq = width * width * (dx * dx + dy * dy); - while (frac_diff * frac_diff < frac_sq) frac_diff++; + int frac_max = 3 * frac_diff / 2; + while (frac_diff < frac_max) { + int frac_test = (frac_diff + frac_max) / 2; + if (frac_test * frac_test < frac_sq) { + frac_diff = frac_test + 1; + } else { + frac_max = frac_test - 1; + } + } } if (dx > dy) { |