git.sesse.net Git - movit/blob - blur_effect.cpp

   1 #include <math.h>
   2 #include <assert.h>
   3
   4 #include "blur_effect.h"
   5 #include "util.h"
   6 #include "opengl.h"
   7
   8 // Must match blur_effect.frag.
   9 #define NUM_TAPS 16
  10
  11 BlurEffect::BlurEffect() {
  12         hpass = new SingleBlurPassEffect();
  13         hpass->set_int("direction", SingleBlurPassEffect::HORIZONTAL);
  14         vpass = new SingleBlurPassEffect();
  15         vpass->set_int("direction", SingleBlurPassEffect::VERTICAL);
  16 }
  17
  18 void BlurEffect::add_self_to_effect_chain(EffectChain *chain, const std::vector<Effect *> &inputs) {
  19         assert(inputs.size() == 1);
  20         hpass->add_self_to_effect_chain(chain, inputs);
  21
  22         std::vector<Effect *> vpass_inputs;
  23         vpass_inputs.push_back(hpass);
  24         vpass->add_self_to_effect_chain(chain, vpass_inputs);
  25 }
  26
  27 bool BlurEffect::set_float(const std::string &key, float value) {
  28         if (!hpass->set_float(key, value)) {
  29                 return false;
  30         }
  31         return vpass->set_float(key, value);
  32 }
  33
  34 SingleBlurPassEffect::SingleBlurPassEffect()
  35         : radius(3.0f),
  36           direction(HORIZONTAL)
  37 {
  38         register_float("radius", (float *)&radius);
  39         register_int("direction", (int *)&direction);
  40 }
  41
  42 std::string SingleBlurPassEffect::output_fragment_shader()
  43 {
  44         return read_file("blur_effect.frag");
  45 }
  46
  47 void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
  48 {
  49         Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
  50
  51         int base_texture_size, texture_size;
  52         if (direction == HORIZONTAL) {
  53                 base_texture_size = texture_size = 1280;  // FIXME
  54         } else if (direction == VERTICAL) {
  55                 base_texture_size = texture_size = 720;  // FIXME
  56         } else {
  57                 assert(false);
  58         }
  59
  60         // We only have 16 taps to work with on each side, and we want that to
  61         // reach out to about 2.5*sigma.  Bump up the mipmap levels (giving us
  62         // box blurs) until we have what we need.
  63         //
  64         // FIXME: we really need to pick the same mipmap level for both horizontal and vertical!
  65         unsigned base_mipmap_level = 0;
  66         float adjusted_radius = radius;
  67         while (texture_size > 1 && adjusted_radius * 2.5f > NUM_TAPS / 2) {
  68                 ++base_mipmap_level;
  69                 texture_size /= 2;  // Rounding down.
  70                 adjusted_radius = radius * float(texture_size) / float(base_texture_size);
  71         }
  72
  73         // In the second pass, we do the same, but don't sample from a mipmap;
  74         // that would re-blur the other direction in an ugly fashion, and we already
  75         // have the vertical box blur we need from that pass.
  76         //
  77         // TODO: We really need to present horizontal+vertical as a unit;
  78         // currently, there's really no guarantee vertical blur is the second pass.
  79         if (direction == VERTICAL) {
  80                 base_mipmap_level = 0;
  81         }
  82
  83         glActiveTexture(GL_TEXTURE0);
  84         check_error();
  85         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, base_mipmap_level);
  86         check_error();
  87         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, base_mipmap_level);
  88         check_error();
  89
  90         // Compute the weights; they will be symmetrical, so we only compute
  91         // the right side.
  92         float weight[NUM_TAPS + 1];
  93         if (radius < 1e-3) {
  94                 weight[0] = 1.0f;
  95                 for (unsigned i = 1; i < NUM_TAPS + 1; ++i) {
  96                         weight[i] = 0.0f;
  97                 }
  98         } else {
  99                 float sum = 0.0f;
 100                 for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
 101                         float z = i / adjusted_radius;
 102
 103                         // Gaussian blur is a common, but maybe not the prettiest choice;
 104                         // it can feel a bit too blurry in the fine detail and too little
 105                         // long-tail. This is a simple logistic distribution, which has
 106                         // a narrower peak but longer tails.
 107                         weight[i] = 1.0f / (cosh(z) * cosh(z));
 108
 109                         if (i == 0) {
 110                                 sum += weight[i];
 111                         } else {
 112                                 sum += 2.0f * weight[i];
 113                         }
 114                 }
 115                 for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
 116                         weight[i] /= sum;
 117                 }
 118         }
 119
 120 #if 0
 121         // NOTE: This is currently broken.
 122
 123         // Since the GPU gives us bilinear sampling for free, we can get two
 124         // samples for the price of one (for every but the center sample,
 125         // in which case this trick doesn't buy us anything). Simply sample
 126         // between the two pixel centers, and we can do with fewer weights.
 127         // (This is right even in the vertical pass where we don't actually
 128         // sample between the pixels, because we have linear interpolation
 129         // there too.)
 130         //
 131         // We pack the parameters into a float4: The relative sample coordinates
 132         // in (x,y), and the weight in z. w is unused.
 133         float samples[4 * (NUM_TAPS / 2 + 1)];
 134
 135         // Center sample.
 136         samples[4 * 0 + 0] = 0.0f;
 137         samples[4 * 0 + 1] = 0.0f;
 138         samples[4 * 0 + 2] = weight[0];
 139         samples[4 * 0 + 3] = 0.0f;
 140
 141         // All other samples.
 142         for (unsigned i = 1; i < NUM_TAPS / 2 + 1; ++i) {
 143                 unsigned base_pos = i * 2 - 1;
 144                 float w1 = weight[base_pos];
 145                 float w2 = weight[base_pos + 1];
 146
 147                 float offset, total_weight;
 148                 if (w1 + w2 < 1e-6) {
 149                         offset = 0.5f;
 150                         total_weight = 0.0f;
 151                 } else {
 152                         offset = w2 / (w1 + w2);
 153                         total_weight = w1 + w2;
 154                 }
 155 #if 0
 156                 // hack for easier visualization
 157                 offset = 0.5f;
 158                 total_weight = 8.0f;
 159 #endif
 160                 float x = 0.0f, y = 0.0f;
 161
 162                 if (direction == HORIZONTAL) {
 163                         x = (base_pos + offset) / (float)texture_size;
 164                 } else if (direction == VERTICAL) {
 165                         y = (base_pos + offset) / (float)texture_size;
 166                 } else {
 167                         assert(false);
 168                 }
 169
 170                 samples[4 * i + 0] = x;
 171                 samples[4 * i + 1] = y;
 172                 samples[4 * i + 2] = total_weight;
 173                 samples[4 * i + 3] = 0.0f;
 174         }
 175
 176         set_uniform_vec4_array(glsl_program_num, prefix, "samples", samples, NUM_TAPS / 2 + 1);
 177 #else
 178         // Boring, at-whole-pixels sampling.
 179         float samples[4 * NUM_TAPS];
 180
 181         // All other samples.
 182         for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
 183                 float x = 0.0f, y = 0.0f;
 184
 185                 if (direction == HORIZONTAL) {
 186                         x = i / (float)texture_size;
 187                 } else if (direction == VERTICAL) {
 188                         y = i / (float)texture_size;
 189                 } else {
 190                         assert(false);
 191                 }
 192
 193                 samples[4 * i + 0] = x;
 194                 samples[4 * i + 1] = y;
 195                 samples[4 * i + 2] = weight[i];
 196                 samples[4 * i + 3] = 0.0f;
 197         }
 198
 199         set_uniform_vec4_array(glsl_program_num, prefix, "samples", samples, NUM_TAPS + 1);
 200 #endif
 201 }
 202
 203 void SingleBlurPassEffect::clear_gl_state()
 204 {
 205         glActiveTexture(GL_TEXTURE0);
 206         check_error();
 207         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
 208         check_error();
 209         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 1000);
 210         check_error();
 211 }