Use the input resolution in the blur instead of hard-coding 1280x720. Also fix mipmap...
[movit] / blur_effect.cpp
1 #include <math.h>
2 #include <assert.h>
3
4 #include "blur_effect.h"
5 #include "effect_chain.h"
6 #include "util.h"
7 #include "opengl.h"
8
9 // Must match blur_effect.frag.
10 #define NUM_TAPS 16
11         
12 BlurEffect::BlurEffect()
13         : radius(3.0f),
14           input_width(1280),
15           input_height(720)
16 {
17         // The first blur pass will forward resolution information to us.
18         hpass = new SingleBlurPassEffect(this);
19         hpass->set_int("direction", SingleBlurPassEffect::HORIZONTAL);
20         vpass = new SingleBlurPassEffect(NULL);
21         vpass->set_int("direction", SingleBlurPassEffect::VERTICAL);
22
23         update_radius();
24 }
25
26 void BlurEffect::rewrite_graph(EffectChain *graph, Node *self)
27 {
28         Node *hpass_node = graph->add_node(hpass);
29         Node *vpass_node = graph->add_node(vpass);
30         graph->connect_nodes(hpass_node, vpass_node);
31         graph->replace_receiver(self, hpass_node);
32         graph->replace_sender(self, vpass_node);
33         self->disabled = true;
34
35
36 // We get this information forwarded from the first blur pass,
37 // since we are not part of the chain ourselves.
38 void BlurEffect::inform_input_size(unsigned input_num, unsigned width, unsigned height)
39 {
40         assert(input_num == 0);
41         assert(width != 0);
42         assert(height != 0);
43         input_width = width;
44         input_height = height;
45         update_radius();
46 }
47                 
48 void BlurEffect::update_radius()
49 {
50         // We only have 16 taps to work with on each side, and we want that to
51         // reach out to about 2.5*sigma. Bump up the mipmap levels (giving us
52         // box blurs) until we have what we need.
53         unsigned mipmap_width = input_width, mipmap_height = input_height;
54         float adjusted_radius = radius;
55         while ((mipmap_width > 1 || mipmap_height > 1) && adjusted_radius * 1.5f > NUM_TAPS / 2) {
56                 // Find the next mipmap size (round down, minimum 1 pixel).
57                 mipmap_width = std::max(mipmap_width / 2, 1u);
58                 mipmap_height = std::max(mipmap_height / 2, 1u);
59
60                 // Approximate when mipmap sizes are odd, but good enough.
61                 adjusted_radius = radius * float(mipmap_width) / float(input_width);
62         }
63         
64         bool ok = hpass->set_float("radius", adjusted_radius);
65         ok |= hpass->set_int("width", mipmap_width);
66         ok |= hpass->set_int("height", mipmap_height);
67
68         ok |= vpass->set_float("radius", adjusted_radius);
69         ok |= vpass->set_int("width", mipmap_width);
70         ok |= vpass->set_int("height", mipmap_height);
71
72         assert(ok);
73 }
74
75 bool BlurEffect::set_float(const std::string &key, float value) {
76         if (key == "radius") {
77                 radius = value;
78                 update_radius();
79                 return true;
80         }
81         return false;
82 }
83
84 SingleBlurPassEffect::SingleBlurPassEffect(BlurEffect *parent)
85         : parent(parent),
86           radius(3.0f),
87           direction(HORIZONTAL),
88           width(1280),
89           height(720)
90 {
91         register_float("radius", &radius);
92         register_int("direction", (int *)&direction);
93         register_int("width", &width);
94         register_int("height", &height);
95 }
96
97 std::string SingleBlurPassEffect::output_fragment_shader()
98 {
99         return read_file("blur_effect.frag");
100 }
101
102 void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
103 {
104         Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
105
106         // Compute the weights; they will be symmetrical, so we only compute
107         // the right side.
108         float weight[NUM_TAPS + 1];
109         if (radius < 1e-3) {
110                 weight[0] = 1.0f;
111                 for (unsigned i = 1; i < NUM_TAPS + 1; ++i) {
112                         weight[i] = 0.0f;
113                 }
114         } else {
115                 float sum = 0.0f;
116                 for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
117                         float z = i / radius;
118
119                         // Gaussian blur is a common, but maybe not the prettiest choice;
120                         // it can feel a bit too blurry in the fine detail and too little
121                         // long-tail. This is a simple logistic distribution, which has
122                         // a narrower peak but longer tails.
123                         weight[i] = 1.0f / (cosh(z) * cosh(z));
124
125                         if (i == 0) {
126                                 sum += weight[i];
127                         } else {
128                                 sum += 2.0f * weight[i];
129                         }
130                 }
131                 for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
132                         weight[i] /= sum;
133                 }
134         }
135
136         // Since the GPU gives us bilinear sampling for free, we can get two
137         // samples for the price of one (for every but the center sample,
138         // in which case this trick doesn't buy us anything). Simply sample
139         // between the two pixel centers, and we can do with fewer weights.
140         // (This is right even in the vertical pass where we don't actually
141         // sample between the pixels, because we have linear interpolation
142         // there too.)
143         //
144         // We pack the parameters into a float4: The relative sample coordinates
145         // in (x,y), and the weight in z. w is unused.
146         float samples[4 * (NUM_TAPS / 2 + 1)];
147
148         // Center sample.
149         samples[4 * 0 + 0] = 0.0f;
150         samples[4 * 0 + 1] = 0.0f;
151         samples[4 * 0 + 2] = weight[0];
152         samples[4 * 0 + 3] = 0.0f;
153
154         // All other samples.
155         for (unsigned i = 1; i < NUM_TAPS / 2 + 1; ++i) {
156                 unsigned base_pos = i * 2 - 1;
157                 float w1 = weight[base_pos];
158                 float w2 = weight[base_pos + 1];
159
160                 float offset, total_weight;
161                 if (w1 + w2 < 1e-6) {
162                         offset = 0.5f;
163                         total_weight = 0.0f;
164                 } else {
165                         offset = w2 / (w1 + w2);
166                         total_weight = w1 + w2;
167                 }
168                 float x = 0.0f, y = 0.0f;
169
170                 if (direction == HORIZONTAL) {
171                         x = (base_pos + offset) / (float)width;
172                 } else if (direction == VERTICAL) {
173                         y = (base_pos + offset) / (float)height;
174                 } else {
175                         assert(false);
176                 }
177
178                 samples[4 * i + 0] = x;
179                 samples[4 * i + 1] = y;
180                 samples[4 * i + 2] = total_weight;
181                 samples[4 * i + 3] = 0.0f;
182         }
183
184         set_uniform_vec4_array(glsl_program_num, prefix, "samples", samples, NUM_TAPS / 2 + 1);
185 }
186
187 void SingleBlurPassEffect::clear_gl_state()
188 {
189 }