+void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
+{
+ Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
+
+ // Compute the weights; they will be symmetrical, so we only compute
+ // the right side.
+ float weight[NUM_TAPS + 1];
+ if (radius < 1e-3) {
+ weight[0] = 1.0f;
+ for (unsigned i = 1; i < NUM_TAPS + 1; ++i) {
+ weight[i] = 0.0f;
+ }
+ } 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.
+ weight[i] = 1.0f / (cosh(z) * cosh(z));
+
+ if (i == 0) {
+ sum += weight[i];
+ } else {
+ sum += 2.0f * weight[i];
+ }
+ }
+ for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
+ weight[i] /= sum;
+ }
+ }
+
+ // Since the GPU gives us bilinear sampling for free, we can get two
+ // samples for the price of one (for every but the center sample,
+ // in which case this trick doesn't buy us anything). Simply sample
+ // between the two pixel centers, and we can do with fewer weights.
+ // (This is right even in the vertical pass where we don't actually
+ // sample between the pixels, because we have linear interpolation
+ // there too.)
+ //
+ // We pack the parameters into a float4: The relative sample coordinates
+ // in (x,y), and the weight in z. w is unused.
+ float samples[4 * (NUM_TAPS / 2 + 1)];
+
+ // Center sample.
+ samples[4 * 0 + 0] = 0.0f;
+ samples[4 * 0 + 1] = 0.0f;
+ samples[4 * 0 + 2] = weight[0];
+ samples[4 * 0 + 3] = 0.0f;
+
+ // All other samples.
+ for (unsigned i = 1; i < NUM_TAPS / 2 + 1; ++i) {
+ unsigned base_pos = i * 2 - 1;
+ float w1 = weight[base_pos];
+ 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;
+ }
+ float x = 0.0f, y = 0.0f;
+
+ if (direction == HORIZONTAL) {
+ x = (base_pos + offset) / (float)width;
+ } else if (direction == VERTICAL) {
+ y = (base_pos + offset) / (float)height;
+ } else {
+ assert(false);
+ }
+
+ samples[4 * i + 0] = x;
+ samples[4 * i + 1] = y;
+ samples[4 * i + 2] = total_weight;
+ samples[4 * i + 3] = 0.0f;
+ }
+
+ set_uniform_vec4_array(glsl_program_num, prefix, "samples", samples, NUM_TAPS / 2 + 1);
+}
+
+void SingleBlurPassEffect::clear_gl_state()