6 #include "blur_effect.h"
7 #include "effect_chain.h"
10 // Must match blur_effect.frag.
13 BlurEffect::BlurEffect()
18 // The first blur pass will forward resolution information to us.
19 hpass = new SingleBlurPassEffect(this);
20 CHECK(hpass->set_int("direction", SingleBlurPassEffect::HORIZONTAL));
21 vpass = new SingleBlurPassEffect(NULL);
22 CHECK(vpass->set_int("direction", SingleBlurPassEffect::VERTICAL));
27 void BlurEffect::rewrite_graph(EffectChain *graph, Node *self)
29 Node *hpass_node = graph->add_node(hpass);
30 Node *vpass_node = graph->add_node(vpass);
31 graph->connect_nodes(hpass_node, vpass_node);
32 graph->replace_receiver(self, hpass_node);
33 graph->replace_sender(self, vpass_node);
34 self->disabled = true;
37 // We get this information forwarded from the first blur pass,
38 // since we are not part of the chain ourselves.
39 void BlurEffect::inform_input_size(unsigned input_num, unsigned width, unsigned height)
41 assert(input_num == 0);
45 input_height = height;
49 void BlurEffect::update_radius()
51 // We only have 16 taps to work with on each side, and we want that to
52 // reach out to about 2.5*sigma. Bump up the mipmap levels (giving us
53 // box blurs) until we have what we need.
54 unsigned mipmap_width = input_width, mipmap_height = input_height;
55 float adjusted_radius = radius;
56 while ((mipmap_width > 1 || mipmap_height > 1) && adjusted_radius * 1.5f > NUM_TAPS / 2) {
57 // Find the next mipmap size (round down, minimum 1 pixel).
58 mipmap_width = std::max(mipmap_width / 2, 1u);
59 mipmap_height = std::max(mipmap_height / 2, 1u);
61 // Approximate when mipmap sizes are odd, but good enough.
62 adjusted_radius = radius * float(mipmap_width) / float(input_width);
65 bool ok = hpass->set_float("radius", adjusted_radius);
66 ok |= hpass->set_int("width", mipmap_width);
67 ok |= hpass->set_int("height", mipmap_height);
68 ok |= hpass->set_int("virtual_width", mipmap_width);
69 ok |= hpass->set_int("virtual_height", mipmap_height);
71 ok |= vpass->set_float("radius", adjusted_radius);
72 ok |= vpass->set_int("width", mipmap_width);
73 ok |= vpass->set_int("height", mipmap_height);
74 ok |= vpass->set_int("virtual_width", input_width);
75 ok |= vpass->set_int("virtual_height", input_height);
80 bool BlurEffect::set_float(const std::string &key, float value) {
81 if (key == "radius") {
89 SingleBlurPassEffect::SingleBlurPassEffect(BlurEffect *parent)
92 direction(HORIZONTAL),
96 register_float("radius", &radius);
97 register_int("direction", (int *)&direction);
98 register_int("width", &width);
99 register_int("height", &height);
100 register_int("virtual_width", &virtual_width);
101 register_int("virtual_height", &virtual_height);
104 std::string SingleBlurPassEffect::output_fragment_shader()
106 return read_file("blur_effect.frag");
109 void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
111 Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
113 // Compute the weights; they will be symmetrical, so we only compute
115 float weight[NUM_TAPS + 1];
118 for (unsigned i = 1; i < NUM_TAPS + 1; ++i) {
123 for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
124 // Gaussian blur is a common, but maybe not the prettiest choice;
125 // it can feel a bit too blurry in the fine detail and too little
126 // long-tail. This is a simple logistic distribution, which has
127 // a narrower peak but longer tails.
129 // We interpret the radius as sigma, similar to Gaussian blur.
130 // Wikipedia says that sigma² = pi² s² / 3, which yields:
131 const float s = (sqrt(3.0) / M_PI) * radius;
132 float z = i / (2.0 * s);
134 weight[i] = 1.0f / (cosh(z) * cosh(z));
139 sum += 2.0f * weight[i];
142 for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
147 // Since the GPU gives us bilinear sampling for free, we can get two
148 // samples for the price of one (for every but the center sample,
149 // in which case this trick doesn't buy us anything). Simply sample
150 // between the two pixel centers, and we can do with fewer weights.
151 // (This is right even in the vertical pass where we don't actually
152 // sample between the pixels, because we have linear interpolation
155 // We pack the parameters into a float4: The relative sample coordinates
156 // in (x,y), and the weight in z. w is unused.
157 float samples[4 * (NUM_TAPS / 2 + 1)];
160 samples[4 * 0 + 0] = 0.0f;
161 samples[4 * 0 + 1] = 0.0f;
162 samples[4 * 0 + 2] = weight[0];
163 samples[4 * 0 + 3] = 0.0f;
165 // All other samples.
166 for (unsigned i = 1; i < NUM_TAPS / 2 + 1; ++i) {
167 unsigned base_pos = i * 2 - 1;
168 float w1 = weight[base_pos];
169 float w2 = weight[base_pos + 1];
171 float offset, total_weight;
172 combine_two_samples(w1, w2, &offset, &total_weight, NULL);
174 float x = 0.0f, y = 0.0f;
176 if (direction == HORIZONTAL) {
177 x = (base_pos + offset) / (float)width;
178 } else if (direction == VERTICAL) {
179 y = (base_pos + offset) / (float)height;
184 samples[4 * i + 0] = x;
185 samples[4 * i + 1] = y;
186 samples[4 * i + 2] = total_weight;
187 samples[4 * i + 3] = 0.0f;
190 set_uniform_vec4_array(glsl_program_num, prefix, "samples", samples, NUM_TAPS / 2 + 1);
193 void SingleBlurPassEffect::clear_gl_state()