text: /*
   * 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 2016, Blender Foundation.
   */
  
  /** \file
   * \ingroup draw_engine
   *
   * Implementation of Blender Mist pass.
   * IMPORTANT: This is a "post process" of the Z depth so it will lack any transparent objects.
   */
  
  #include "DRW_engine.h"
  #include "DRW_render.h"
  
  #include "DNA_world_types.h"
  
  #include "BLI_string_utils.h"
  
  #include "eevee_private.h"
  
  extern char datatoc_common_view_lib_glsl[];
  extern char datatoc_common_uniforms_lib_glsl[];
  extern char datatoc_bsdf_common_lib_glsl[];
  extern char datatoc_effect_mist_frag_glsl[];
  
  static struct {
    struct GPUShader *mist_sh;
  } e_data = {NULL}; /* Engine data */
  
  void EEVEE_mist_output_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
  {
    const DRWContextState *draw_ctx = DRW_context_state_get();
    EEVEE_FramebufferList *fbl = vedata->fbl;
    DefaultTextureList *dtxl = DRW_viewport_texture_list_get();
    EEVEE_TextureList *txl = vedata->txl;
    EEVEE_StorageList *stl = vedata->stl;
    EEVEE_PassList *psl = vedata->psl;
    EEVEE_EffectsInfo *effects = stl->effects;
    EEVEE_PrivateData *g_data = stl->g_data;
    Scene *scene = draw_ctx->scene;
  
    float clear[4] = {0.0f, 0.0f, 0.0f, 0.0f};
  
    if (e_data.mist_sh == NULL) {
      char *frag_str = BLI_string_joinN(datatoc_common_view_lib_glsl,
                                        datatoc_common_uniforms_lib_glsl,
                                        datatoc_bsdf_common_lib_glsl,
                                        datatoc_effect_mist_frag_glsl);
  
      e_data.mist_sh = DRW_shader_create_fullscreen(frag_str, "#define FIRST_PASS\n");
  
      MEM_freeN(frag_str);
    }
  
    /* Create FrameBuffer. */
  
    /* Should be enough precision for many samples. */
    DRW_texture_ensure_fullscreen_2d(&txl->mist_accum, GPU_R32F, 0);
  
    GPU_framebuffer_ensure_config(&fbl->mist_accum_fb,
                                  {GPU_ATTACHMENT_NONE, GPU_ATTACHMENT_TEXTURE(txl->mist_accum)});
  
    /* Clear texture. */
    if (DRW_state_is_image_render() || effects->taa_current_sample == 1) {
      GPU_framebuffer_bind(fbl->mist_accum_fb);
      GPU_framebuffer_clear_color(fbl->mist_accum_fb, clear);
    }
  
    /* Mist settings. */
    if (scene && scene->world) {
      g_data->mist_start = scene->world->miststa;
      g_data->mist_inv_dist = (scene->world->mistdist > 0.0f) ? 1.0f / scene->world->mistdist : 0.0f;
  
      switch (scene->world->mistype) {
        case WO_MIST_QUADRATIC:
          g_data->mist_falloff = 2.0f;
          break;
        case WO_MIST_LINEAR:
          g_data->mist_falloff = 1.0f;
          break;
        case WO_MIST_INVERSE_QUADRATIC:
          g_data->mist_falloff = 0.5f;
          break;
      }
    }
    else {
      float near = -sldata->common_data.view_vecs[0][2];
      float range = sldata->common_data.view_vecs[1][2];
      /* Fallback */
      g_data->mist_start = near;
      g_data->mist_inv_dist = 1.0f / fabsf(range);
      g_data->mist_falloff = 1.0f;
    }
  
    /* XXX ??!! WHY? If not it does not match cycles. */
    g_data->mist_falloff *= 0.5f;
  
    /* Create Pass and shgroup. */
    DRW_PASS_CREATE(psl->mist_accum_ps, DRW_STATE_WRITE_COLOR | DRW_STATE_BLEND_ADD);
    DRWShadingGroup *grp = DRW_shgroup_create(e_data.mist_sh, psl->mist_accum_ps);
    DRW_shgroup_uniform_texture_ref(grp, "depthBuffer", &dtxl->depth);
    DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
    DRW_shgroup_uniform_block(
        grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
    DRW_shgroup_uniform_vec3(grp, "mistSettings", &g_data->mist_start, 1);
    DRW_shgroup_call(grp, DRW_cache_fullscreen_quad_get(), NULL);
  }
  
  void EEVEE_mist_output_accumulate(EEVEE_ViewLayerData *UNUSED(sldata), EEVEE_Data *vedata)
  {
    EEVEE_FramebufferList *fbl = vedata->fbl;
    EEVEE_PassList *psl = vedata->psl;
  
    if (fbl->mist_accum_fb != NULL) {
      GPU_framebuffer_bind(fbl->mist_accum_fb);
      DRW_draw_pass(psl->mist_accum_ps);
  
      /* Restore */
      GPU_framebuffer_bind(fbl->main_fb);
    }
  }
  
  void EEVEE_mist_free(void)
  {
    DRW_SHADER_FREE_SAFE(e_data.mist_sh);
  }
  