6 #include "blur_effect.h"
7 #include "effect_chain.h"
8 #include "effect_util.h"
11 // Must match blur_effect.frag.
18 BlurEffect::BlurEffect()
23 // The first blur pass will forward resolution information to us.
24 hpass = new SingleBlurPassEffect(this);
25 CHECK(hpass->set_int("direction", SingleBlurPassEffect::HORIZONTAL));
26 vpass = new SingleBlurPassEffect(NULL);
27 CHECK(vpass->set_int("direction", SingleBlurPassEffect::VERTICAL));
32 void BlurEffect::rewrite_graph(EffectChain *graph, Node *self)
34 Node *hpass_node = graph->add_node(hpass);
35 Node *vpass_node = graph->add_node(vpass);
36 graph->connect_nodes(hpass_node, vpass_node);
37 graph->replace_receiver(self, hpass_node);
38 graph->replace_sender(self, vpass_node);
39 self->disabled = true;
42 // We get this information forwarded from the first blur pass,
43 // since we are not part of the chain ourselves.
44 void BlurEffect::inform_input_size(unsigned input_num, unsigned width, unsigned height)
46 assert(input_num == 0);
50 input_height = height;
54 void BlurEffect::update_radius()
56 // We only have 16 taps to work with on each side, and we want that to
57 // reach out to about 2.5*sigma. Bump up the mipmap levels (giving us
58 // box blurs) until we have what we need.
59 unsigned mipmap_width = input_width, mipmap_height = input_height;
60 float adjusted_radius = radius;
61 while ((mipmap_width > 1 || mipmap_height > 1) && adjusted_radius * 1.5f > NUM_TAPS / 2) {
62 // Find the next mipmap size (round down, minimum 1 pixel).
63 mipmap_width = max(mipmap_width / 2, 1u);
64 mipmap_height = max(mipmap_height / 2, 1u);
66 // Approximate when mipmap sizes are odd, but good enough.
67 adjusted_radius = radius * float(mipmap_width) / float(input_width);
70 bool ok = hpass->set_float("radius", adjusted_radius);
71 ok |= hpass->set_int("width", mipmap_width);
72 ok |= hpass->set_int("height", mipmap_height);
73 ok |= hpass->set_int("virtual_width", mipmap_width);
74 ok |= hpass->set_int("virtual_height", mipmap_height);
76 ok |= vpass->set_float("radius", adjusted_radius);
77 ok |= vpass->set_int("width", mipmap_width);
78 ok |= vpass->set_int("height", mipmap_height);
79 ok |= vpass->set_int("virtual_width", input_width);
80 ok |= vpass->set_int("virtual_height", input_height);
85 bool BlurEffect::set_float(const string &key, float value) {
86 if (key == "radius") {
94 SingleBlurPassEffect::SingleBlurPassEffect(BlurEffect *parent)
97 direction(HORIZONTAL),
101 register_float("radius", &radius);
102 register_int("direction", (int *)&direction);
103 register_int("width", &width);
104 register_int("height", &height);
105 register_int("virtual_width", &virtual_width);
106 register_int("virtual_height", &virtual_height);
109 string SingleBlurPassEffect::output_fragment_shader()
111 return read_file("blur_effect.frag");
114 void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, unsigned *sampler_num)
116 Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
118 // Compute the weights; they will be symmetrical, so we only compute
120 float weight[NUM_TAPS + 1];
123 for (unsigned i = 1; i < NUM_TAPS + 1; ++i) {
128 for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
129 // Gaussian blur is a common, but maybe not the prettiest choice;
130 // it can feel a bit too blurry in the fine detail and too little
131 // long-tail. This is a simple logistic distribution, which has
132 // a narrower peak but longer tails.
134 // We interpret the radius as sigma, similar to Gaussian blur.
135 // Wikipedia says that sigma² = pi² s² / 3, which yields:
136 const float s = (sqrt(3.0) / M_PI) * radius;
137 float z = i / (2.0 * s);
139 weight[i] = 1.0f / (cosh(z) * cosh(z));
144 sum += 2.0f * weight[i];
147 for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
152 // Since the GPU gives us bilinear sampling for free, we can get two
153 // samples for the price of one (for every but the center sample,
154 // in which case this trick doesn't buy us anything). Simply sample
155 // between the two pixel centers, and we can do with fewer weights.
156 // (This is right even in the vertical pass where we don't actually
157 // sample between the pixels, because we have linear interpolation
160 // We pack the parameters into a float4: The relative sample coordinates
161 // in (x,y), and the weight in z. w is unused.
162 float samples[4 * (NUM_TAPS / 2 + 1)];
165 samples[4 * 0 + 0] = 0.0f;
166 samples[4 * 0 + 1] = 0.0f;
167 samples[4 * 0 + 2] = weight[0];
168 samples[4 * 0 + 3] = 0.0f;
170 // All other samples.
171 for (unsigned i = 1; i < NUM_TAPS / 2 + 1; ++i) {
172 unsigned base_pos = i * 2 - 1;
173 float w1 = weight[base_pos];
174 float w2 = weight[base_pos + 1];
176 float offset, total_weight;
177 combine_two_samples(w1, w2, &offset, &total_weight, NULL);
179 float x = 0.0f, y = 0.0f;
181 if (direction == HORIZONTAL) {
182 x = (base_pos + offset) / (float)width;
183 } else if (direction == VERTICAL) {
184 y = (base_pos + offset) / (float)height;
189 samples[4 * i + 0] = x;
190 samples[4 * i + 1] = y;
191 samples[4 * i + 2] = total_weight;
192 samples[4 * i + 3] = 0.0f;
195 set_uniform_vec4_array(glsl_program_num, prefix, "samples", samples, NUM_TAPS / 2 + 1);
198 void SingleBlurPassEffect::clear_gl_state()