eevee_lut_gen.c

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/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * Copyright 2020, Blender Foundation.
 */
 
#include "DRW_render.h"
 
#include "BLI_fileops.h"
#include "BLI_rand.h"
#include "BLI_string_utils.h"
 
#include "eevee_private.h"
 
#define DO_FILE_OUTPUT 0
 
float *EEVEE_lut_update_ggx_brdf(int lut_size)
{
  DRWPass *pass = DRW_pass_create(__func__, DRW_STATE_WRITE_COLOR);
  DRWShadingGroup *grp = DRW_shgroup_create(EEVEE_shaders_ggx_lut_sh_get(), pass);
  DRW_shgroup_uniform_float_copy(grp, "sampleCount", 64.0f); /* Actual sample count is squared. */
  DRW_shgroup_call_procedural_triangles(grp, NULL, 1);
 
  GPUTexture *tex = DRW_texture_create_2d(lut_size, lut_size, GPU_RG16F, 0, NULL);
  GPUFrameBuffer *fb = NULL;
  GPU_framebuffer_ensure_config(&fb,
                                {
                                    GPU_ATTACHMENT_NONE,
                                    GPU_ATTACHMENT_TEXTURE(tex),
                                });
  GPU_framebuffer_bind(fb);
  DRW_draw_pass(pass);
  GPU_FRAMEBUFFER_FREE_SAFE(fb);
 
  float *data = GPU_texture_read(tex, GPU_DATA_FLOAT, 0);
  GPU_texture_free(tex);
#if DO_FILE_OUTPUT
  /* Content is to be put inside eevee_lut.c */
  FILE *f = BLI_fopen("bsdf_split_sum_ggx.h", "w");
  fprintf(f, "const float bsdf_split_sum_ggx[%d * %d * 2] = {", lut_size, lut_size);
  for (int i = 0; i < lut_size * lut_size * 2;) {
    fprintf(f, "\n    ");
    for (int j = 0; j < 4; j++, i += 2) {
      fprintf(f, "%ff, %ff, ", data[i], data[i + 1]);
    }
  }
  fprintf(f, "\n};\n");
  fclose(f);
#endif
 
  return data;
}
 
float *EEVEE_lut_update_ggx_btdf(int lut_size, int lut_depth)
{
  float roughness;
  DRWPass *pass = DRW_pass_create(__func__, DRW_STATE_WRITE_COLOR);
  DRWShadingGroup *grp = DRW_shgroup_create(EEVEE_shaders_ggx_refraction_lut_sh_get(), pass);
  DRW_shgroup_uniform_float_copy(grp, "sampleCount", 64.0f); /* Actual sample count is squared. */
  DRW_shgroup_uniform_float(grp, "z", &roughness, 1);
  DRW_shgroup_call_procedural_triangles(grp, NULL, 1);
 
  GPUTexture *tex = DRW_texture_create_2d_array(lut_size, lut_size, lut_depth, GPU_RG16F, 0, NULL);
  GPUFrameBuffer *fb = NULL;
  for (int i = 0; i < lut_depth; i++) {
    GPU_framebuffer_ensure_config(&fb,
                                  {
                                      GPU_ATTACHMENT_NONE,
                                      GPU_ATTACHMENT_TEXTURE_LAYER(tex, i),
                                  });
    GPU_framebuffer_bind(fb);
    roughness = i / (lut_depth - 1.0f);
    DRW_draw_pass(pass);
  }
 
  GPU_FRAMEBUFFER_FREE_SAFE(fb);
 
  float *data = GPU_texture_read(tex, GPU_DATA_FLOAT, 0);
  GPU_texture_free(tex);
 
#if DO_FILE_OUTPUT
  /* Content is to be put inside eevee_lut.c. Don't forget to format the output. */
  FILE *f = BLI_fopen("btdf_split_sum_ggx.h", "w");
  fprintf(f, "const float btdf_split_sum_ggx[%d][%d * %d * 2] = {", lut_depth, lut_size, lut_size);
  fprintf(f, "\n    ");
  int ofs = 0;
  for (int d = 0; d < lut_depth; d++) {
    fprintf(f, "{\n");
    for (int i = 0; i < lut_size * lut_size * 2;) {
      for (int j = 0; j < 4; j++, i += 2, ofs += 2) {
        fprintf(f, "%ff, %ff, ", data[ofs], data[ofs + 1]);
      }
      fprintf(f, "\n    ");
    }
    fprintf(f, "},\n");
  }
  fprintf(f, "};\n");
  fclose(f);
#endif
 
  return data;
}