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

   1 #include <GL/glew.h>
   2
   3 #include "init.h"
   4 #include "util.h"
   5
   6 bool movit_initialized = false;
   7 float movit_texel_subpixel_precision;
   8 bool movit_srgb_textures_supported;
   9
  10 namespace {
  11
  12 void measure_texel_subpixel_precision()
  13 {
  14         static const unsigned width = 1024;
  15
  16         // Generate a destination texture to render to, and an FBO.
  17         GLuint dst_texnum, fbo;
  18
  19         glGenTextures(1, &dst_texnum);
  20         check_error();
  21         glBindTexture(GL_TEXTURE_2D, dst_texnum);
  22         check_error();
  23         glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F_ARB, width, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
  24         check_error();
  25
  26         glGenFramebuffers(1, &fbo);
  27         check_error();
  28         glBindFramebuffer(GL_FRAMEBUFFER, fbo);
  29         check_error();
  30         glFramebufferTexture2D(
  31                 GL_FRAMEBUFFER,
  32                 GL_COLOR_ATTACHMENT0,
  33                 GL_TEXTURE_2D,
  34                 dst_texnum,
  35                 0);
  36         check_error();
  37
  38         // Now generate a simple texture that's just [0,1].
  39         GLuint src_texnum;
  40         float texdata[] = { 0, 1 };
  41         glGenTextures(1, &dst_texnum);
  42         check_error();
  43         glBindTexture(GL_TEXTURE_1D, dst_texnum);
  44         check_error();
  45         glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  46         check_error();
  47         glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  48         check_error();
  49         glTexImage1D(GL_TEXTURE_1D, 0, GL_LUMINANCE16F_ARB, 2, 0, GL_LUMINANCE, GL_FLOAT, texdata);
  50         check_error();
  51         glEnable(GL_TEXTURE_1D);
  52         check_error();
  53
  54         // Basic state.
  55         glDisable(GL_BLEND);
  56         check_error();
  57         glDisable(GL_DEPTH_TEST);
  58         check_error();
  59         glDepthMask(GL_FALSE);
  60         check_error();
  61
  62         glViewport(0, 0, width, 1);
  63
  64         glMatrixMode(GL_PROJECTION);
  65         glLoadIdentity();
  66         glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0);
  67
  68         glMatrixMode(GL_MODELVIEW);
  69         glLoadIdentity();
  70         check_error();
  71
  72         // Draw the texture stretched over a long quad, interpolating it out.
  73         // Note that since the texel center is in (0.5), we need to adjust the
  74         // texture coordinates in order not to get long stretches of (1,1,1,...)
  75         // at the start and (...,0,0,0) at the end.
  76         glBegin(GL_QUADS);
  77
  78         glTexCoord1f(0.25f);
  79         glVertex2f(0.0f, 0.0f);
  80
  81         glTexCoord1f(0.75f);
  82         glVertex2f(1.0f, 0.0f);
  83
  84         glTexCoord1f(0.75f);
  85         glVertex2f(1.0f, 1.0f);
  86
  87         glTexCoord1f(0.25f);
  88         glVertex2f(0.0f, 1.0f);
  89
  90         glEnd();
  91         check_error();
  92
  93         glDisable(GL_TEXTURE_1D);
  94         check_error();
  95
  96         // Now read the data back and see what the card did.
  97         // (We only look at the red channel; the others will surely be the same.)
  98         // We assume a linear ramp; anything else will give sort of odd results here.
  99         float out_data[width];
 100         glReadPixels(0, 0, width, 1, GL_RED, GL_FLOAT, out_data);
 101         check_error();
 102
 103         float biggest_jump = 0.0f;
 104         for (unsigned i = 1; i < width; ++i) {
 105                 assert(out_data[i] >= out_data[i - 1]);
 106                 biggest_jump = std::max(biggest_jump, out_data[i] - out_data[i - 1]);
 107         }
 108
 109         movit_texel_subpixel_precision = biggest_jump;
 110
 111         // Clean up.
 112         glBindTexture(GL_TEXTURE_1D, 0);
 113         check_error();
 114         glBindFramebuffer(GL_FRAMEBUFFER, 0);
 115         check_error();
 116         glDeleteFramebuffers(1, &fbo);
 117         check_error();
 118         glDeleteTextures(1, &dst_texnum);
 119         check_error();
 120         glDeleteTextures(1, &src_texnum);
 121         check_error();
 122 }
 123
 124 void check_extensions()
 125 {
 126         // We fundamentally need FBOs and floating-point textures.
 127         assert(glewIsSupported("GL_ARB_framebuffer_object") != 0);
 128         assert(glewIsSupported("GL_ARB_texture_float") != 0);
 129
 130         // We assume that we can use non-power-of-two textures without restrictions.
 131         assert(glewIsSupported("GL_ARB_texture_non_power_of_two") != 0);
 132
 133         // We also need GLSL fragment shaders.
 134         assert(glewIsSupported("GL_ARB_fragment_shader") != 0);
 135         assert(glewIsSupported("GL_ARB_shading_language_100") != 0);
 136
 137         // FlatInput and YCbCrInput uses PBOs. (They could in theory do without,
 138         // but no modern card would really not provide it.)
 139         assert(glewIsSupported("GL_ARB_pixel_buffer_object") != 0);
 140
 141         // ResampleEffect uses RG textures to encode a two-component LUT.
 142         assert(glewIsSupported("GL_ARB_texture_rg") != 0);
 143
 144         // sRGB texture decode would be nice, but are not mandatory
 145         // (GammaExpansionEffect can do the same thing if needed).
 146         movit_srgb_textures_supported = glewIsSupported("GL_EXT_texture_sRGB");
 147 }
 148
 149 }  // namespace
 150
 151 void init_movit()
 152 {
 153         if (movit_initialized) {
 154                 return;
 155         }
 156
 157         glewInit();
 158
 159         // geez
 160         glPixelStorei(GL_PACK_ALIGNMENT, 1);
 161         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 162
 163         measure_texel_subpixel_precision();
 164         check_extensions();
 165
 166         movit_initialized = true;
 167 }