Factorize the code to compute sampling points for bilinear sampling into a shared...

diff --git a/blur_effect.cpp b/blur_effect.cpp
index 579521fde00b2e952824681bf5dcaa1aea178e7e..90d1b68653b9af51c009c1fae48a7e007998da8d 100644 (file)
--- a/blur_effect.cpp
+++ b/blur_effect.cpp
@@ -162,13 +162,8 @@ void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const std::stri
                float w2 = weight[base_pos + 1];
 
                float offset, total_weight;
-               if (w1 + w2 < 1e-6) {
-                       offset = 0.5f;
-                       total_weight = 0.0f;
-               } else {
-                       offset = w2 / (w1 + w2);
-                       total_weight = w1 + w2;
-               }
+               combine_two_samples(w1, w2, &offset, &total_weight);
+
                float x = 0.0f, y = 0.0f;
 
                if (direction == HORIZONTAL) {

diff --git a/util.h b/util.h
index b53bac76ce742367c618e47d1a4578d926bb8cd8..432171ac015d3fd5921b5eb9fe9c0ccffd92b9b3 100644 (file)
--- a/util.h
+++ b/util.h
@@ -34,6 +34,22 @@ void print_3x3_matrix(const Eigen::Matrix3d &m);
 // Output a GLSL 3x3 matrix declaration.
 std::string output_glsl_mat3(const std::string &name, const Eigen::Matrix3d &m);
 
+// Calculate where to sample, and with what weight, if one wants to use
+// the GPU's bilinear hardware to sample w1 * x[0] + w2 * x[1].
+static inline void combine_two_samples(float w1, float w2, float *offset, float *total_weight)
+{
+       assert(w1 * w2 >= 0.0f);  // Should not have differing signs.
+       if (fabs(w1 + w2) < 1e-6) {
+               *offset = 0.5f;
+               *total_weight = 0.0f;
+       } else {
+               *offset = w2 / (w1 + w2);
+               *total_weight = w1 + w2;
+       }
+       assert(*offset >= 0.0f);
+       assert(*offset <= 1.0f);
+}
+
 #ifdef NDEBUG
 #define check_error()
 #else