From e7389a6a3041dcb1a0a4dceffd2ca9018b49b2f2 Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" Date: Sat, 13 Oct 2012 13:31:01 +0200 Subject: [PATCH] Radius calculation in the blur was about 10% off. Probably impossible to notice, but I guess nice to fix. --- blur_effect.cpp | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/blur_effect.cpp b/blur_effect.cpp index b48dc95..579521f 100644 --- a/blur_effect.cpp +++ b/blur_effect.cpp @@ -114,12 +114,16 @@ void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const std::stri } else { float sum = 0.0f; for (unsigned i = 0; i < NUM_TAPS + 1; ++i) { - float z = i / radius; - // Gaussian blur is a common, but maybe not the prettiest choice; // it can feel a bit too blurry in the fine detail and too little // long-tail. This is a simple logistic distribution, which has // a narrower peak but longer tails. + // + // We interpret the radius as sigma, similar to Gaussian blur. + // Wikipedia says that sigma² = pi² s² / 3, which yields: + const float s = (sqrt(3.0) / M_PI) * radius; + float z = i / (2.0 * s); + weight[i] = 1.0f / (cosh(z) * cosh(z)); if (i == 0) { -- 2.39.2