test2/source/blender/draw/engines/eevee/shaders/eevee_cryptomatte_lib.glsl

/* SPDX-FileCopyrightText: 2022 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

#pragma once

#include "infos/eevee_film_infos.hh"

SHADER_LIBRARY_CREATE_INFO(eevee_film)

/** Storing/merging and sorting cryptomatte samples. */

bool cryptomatte_can_merge_sample(float2 dst, float2 src)
{
  if (all(equal(dst, float2(0.0f, 0.0f)))) {
    return true;
  }
  if (dst.x == src.x) {
    return true;
  }
  return false;
}

float2 cryptomatte_merge_sample(FilmSample film_sample, float2 dst, float2 src)
{
  return float2(src.x, (dst.y * film_sample.weight + src.y) * film_sample.weight_sum_inv);
}

float4 cryptomatte_false_color(float hash)
{
  uint m3hash = floatBitsToUint(hash);
  return float4(hash,
                float(m3hash << 8) / float(0xFFFFFFFFu),
                float(m3hash << 16) / float(0xFFFFFFFFu),
                1.0f);
}

void cryptomatte_clear_samples(FilmSample dst)
{
  int layer_len = imageSize(cryptomatte_img).z;
  for (int i = 0; i < layer_len; i++) {
    imageStoreFast(cryptomatte_img, int3(dst.texel, i), float4(0.0f));
    /* Ensure stores are visible to later reads. */
    imageFence(cryptomatte_img);
  }
}

void cryptomatte_store_film_sample(FilmSample dst,
                                   int cryptomatte_layer_id,
                                   float2 crypto_sample,
                                   out float4 out_color)
{
  if (crypto_sample.y == 0.0f) {
    return;
  }
  for (int i = 0; i < uniform_buf.film.cryptomatte_samples_len / 2; i++) {
    int3 img_co = int3(dst.texel, cryptomatte_layer_id + i);
    float4 sample_pair = imageLoad(cryptomatte_img, img_co);
    if (cryptomatte_can_merge_sample(sample_pair.xy, crypto_sample)) {
      sample_pair.xy = cryptomatte_merge_sample(dst, sample_pair.xy, crypto_sample);
      /* In viewport only one layer is active. */
      /* TODO(jbakker):  we are displaying the first sample, but we should display the highest
       * weighted one. */
      if (cryptomatte_layer_id + i == 0) {
        out_color = cryptomatte_false_color(sample_pair.x);
      }
    }
    else if (cryptomatte_can_merge_sample(sample_pair.zw, crypto_sample)) {
      sample_pair.zw = cryptomatte_merge_sample(dst, sample_pair.zw, crypto_sample);
    }
    else if (i == uniform_buf.film.cryptomatte_samples_len / 2 - 1) {
      /* TODO(jbakker): New hash detected, but there is no space left to store it. Currently we
       * will ignore this sample, but ideally we could replace a sample with a lowest weight. */
      continue;
    }
    else {
      continue;
    }
    imageStoreFast(cryptomatte_img, img_co, sample_pair);
    break;
  }
  /* Ensure stores are visible to later reads. */
  imageFence(cryptomatte_img);
}