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

   1 #define GL_GLEXT_PROTOTYPES 1
   2
   3 #include <math.h>
   4 #include <GL/gl.h>
   5 #include <GL/glext.h>
   6 #include <assert.h>
   7
   8 #include "blur_effect.h"
   9 #include "util.h"
  10
  11 BlurEffect::BlurEffect()
  12         : radius(3.0f),
  13           direction(HORIZONTAL)
  14 {
  15         register_float("radius", (float *)&radius);
  16         register_int("direction", (int *)&direction);
  17 }
  18
  19 std::string BlurEffect::output_fragment_shader()
  20 {
  21         return read_file("blur_effect.frag");
  22 }
  23
  24 void BlurEffect::set_uniforms(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
  25 {
  26         Effect::set_uniforms(glsl_program_num, prefix, sampler_num);
  27
  28         // We only have 15 taps to work with, and we want that to reach out to about 2.5*sigma.
  29         // Bump up the mipmap levels (giving us box blurs) until we have what we need.
  30         unsigned base_mipmap_level = 0;
  31         float adjusted_radius = radius;
  32         float pixel_size = 1.0f;
  33         while (adjusted_radius * 2.5f > 7.0f) {
  34                 ++base_mipmap_level;
  35                 adjusted_radius *= 0.5f;
  36                 pixel_size *= 2.0f;
  37         }
  38
  39         // In the second pass, we do the same, but don't sample from a mipmap;
  40         // that would re-blur the other direction in an ugly fashion, and we already
  41         // have the vertical box blur we need from that pass.
  42         //
  43         // TODO: We really need to present horizontal+vertical as a unit;
  44         // currently, there's really no guarantee vertical blur is the second pass.
  45         if (direction == VERTICAL) {
  46                 base_mipmap_level = 0;
  47         }
  48
  49         glActiveTexture(GL_TEXTURE0);
  50         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, base_mipmap_level);
  51         check_error();
  52
  53         // FIXME
  54         if (direction == HORIZONTAL) {
  55                 float ps[] = { pixel_size / 1280.0f, 0.0f };
  56                 set_uniform_vec2(glsl_program_num, prefix, "pixel_offset", ps);
  57         } else if (direction == VERTICAL) {
  58                 float ps[] = { 0.0f, pixel_size / 720.0f };
  59                 set_uniform_vec2(glsl_program_num, prefix, "pixel_offset", ps);
  60         } else {
  61                 assert(false);
  62         }
  63
  64         // Simple Gaussian weights for now.
  65         float weight[15], total = 0.0f;
  66         for (unsigned i = 0; i < 15; ++i) {
  67                 float z = (i - 7.0f) / adjusted_radius;
  68                 weight[i] = exp(-(z*z));
  69                 total += weight[i];
  70         }
  71         printf("[mip level %d] ", base_mipmap_level);
  72         for (unsigned i = 0; i < 15; ++i) {
  73                 weight[i] /= total;
  74                 printf("%f ", weight[i]);
  75         }
  76         printf("\n");
  77         set_uniform_float_array(glsl_program_num, prefix, "weight", weight, 15);
  78 }