Tweak cryptomatte channels naming to improve interoperability

Use lowercase rgba channel names which still by-passes lossy nature
of DWA compression and which also keeps external compositing tools
happy.

Thanks Steffen Dünner for testing this patch!

Differential Revision: https://developer.blender.org/D15834

2 files changed, 12 insertions, 12 deletions

diff --git a/intern/cycles/blender/sync.cpp b/intern/cycles/blender/sync.cpp
index 9bd0abe2773..3808cbf1459 100644
--- a/intern/cycles/blender/sync.cpp
+++ b/intern/cycles/blender/sync.cpp
@@ -682,16 +682,16 @@ void BlenderSync::sync_render_passes(BL::RenderLayer &b_rlay, BL::ViewLayer &b_v
   /* Cryptomatte stores two ID/weight pairs per RGBA layer.
    * User facing parameter is the number of pairs.
    *
-   * NOTE: Name channels lowercase xyzw so that compression rules check in OpenEXR DWA code uses
-   * loseless compression. It is important to use lowercase since the capital Y uses lossy
-   * compression in DWA. */
+   * NOTE: Name channels lowercase rgba so that compression rules check in OpenEXR DWA code uses
+   * loseless compression. Reportedly this naming is the only one which works good from the
+   * interoperability point of view. Using xyzw naming is not portable. */
   int crypto_depth = divide_up(min(16, b_view_layer.pass_cryptomatte_depth()), 2);
   scene->film->set_cryptomatte_depth(crypto_depth);
   CryptomatteType cryptomatte_passes = CRYPT_NONE;
   if (b_view_layer.use_pass_cryptomatte_object()) {
     for (int i = 0; i < crypto_depth; i++) {
       string passname = cryptomatte_prefix + string_printf("Object%02d", i);
-      b_engine.add_pass(passname.c_str(), 4, "xyzw", b_view_layer.name().c_str());
+      b_engine.add_pass(passname.c_str(), 4, "rgba", b_view_layer.name().c_str());
       pass_add(scene, PASS_CRYPTOMATTE, passname.c_str());
     }
     cryptomatte_passes = (CryptomatteType)(cryptomatte_passes | CRYPT_OBJECT);
@@ -699,7 +699,7 @@ void BlenderSync::sync_render_passes(BL::RenderLayer &b_rlay, BL::ViewLayer &b_v
   if (b_view_layer.use_pass_cryptomatte_material()) {
     for (int i = 0; i < crypto_depth; i++) {
       string passname = cryptomatte_prefix + string_printf("Material%02d", i);
-      b_engine.add_pass(passname.c_str(), 4, "xyzw", b_view_layer.name().c_str());
+      b_engine.add_pass(passname.c_str(), 4, "rgba", b_view_layer.name().c_str());
       pass_add(scene, PASS_CRYPTOMATTE, passname.c_str());
     }
     cryptomatte_passes = (CryptomatteType)(cryptomatte_passes | CRYPT_MATERIAL);
@@ -707,7 +707,7 @@ void BlenderSync::sync_render_passes(BL::RenderLayer &b_rlay, BL::ViewLayer &b_v
   if (b_view_layer.use_pass_cryptomatte_asset()) {
     for (int i = 0; i < crypto_depth; i++) {
       string passname = cryptomatte_prefix + string_printf("Asset%02d", i);
-      b_engine.add_pass(passname.c_str(), 4, "xyzw", b_view_layer.name().c_str());
+      b_engine.add_pass(passname.c_str(), 4, "rgba", b_view_layer.name().c_str());
       pass_add(scene, PASS_CRYPTOMATTE, passname.c_str());
     }
     cryptomatte_passes = (CryptomatteType)(cryptomatte_passes | CRYPT_ASSET);
diff --git a/source/blender/draw/engines/eevee/eevee_cryptomatte.c b/source/blender/draw/engines/eevee/eevee_cryptomatte.c
index 36ec1354375..fa70d2c6205 100644
--- a/source/blender/draw/engines/eevee/eevee_cryptomatte.c
+++ b/source/blender/draw/engines/eevee/eevee_cryptomatte.c
@@ -421,9 +421,9 @@ void EEVEE_cryptomatte_output_accumulate(EEVEE_ViewLayerData *UNUSED(sldata), EE
 
 void EEVEE_cryptomatte_update_passes(RenderEngine *engine, Scene *scene, ViewLayer *view_layer)
 {
-  /* NOTE: Name channels lowercase xyzw so that compression rules check in OpenEXR DWA code uses
-   * loseless compression. It is important to use lowercase since the capital Y uses lossy
-   * compression in DWA. */
+  /* NOTE: Name channels lowercase rgba so that compression rules check in OpenEXR DWA code uses
+   * loseless compression. Reportedly this naming is the only one which works good from the
+   * interoperability point of view. Using xyzw naming is not portable. */
 
   char cryptomatte_pass_name[MAX_NAME];
   const short num_passes = eevee_cryptomatte_passes_per_layer(view_layer);
@@ -431,21 +431,21 @@ void EEVEE_cryptomatte_update_passes(RenderEngine *engine, Scene *scene, ViewLay
     for (short pass = 0; pass < num_passes; pass++) {
       BLI_snprintf_rlen(cryptomatte_pass_name, MAX_NAME, "CryptoObject%02d", pass);
       RE_engine_register_pass(
-          engine, scene, view_layer, cryptomatte_pass_name, 4, "xyzw", SOCK_RGBA);
+          engine, scene, view_layer, cryptomatte_pass_name, 4, "rgba", SOCK_RGBA);
     }
   }
   if ((view_layer->cryptomatte_flag & VIEW_LAYER_CRYPTOMATTE_MATERIAL) != 0) {
     for (short pass = 0; pass < num_passes; pass++) {
       BLI_snprintf_rlen(cryptomatte_pass_name, MAX_NAME, "CryptoMaterial%02d", pass);
       RE_engine_register_pass(
-          engine, scene, view_layer, cryptomatte_pass_name, 4, "xyzw", SOCK_RGBA);
+          engine, scene, view_layer, cryptomatte_pass_name, 4, "rgba", SOCK_RGBA);
     }
   }
   if ((view_layer->cryptomatte_flag & VIEW_LAYER_CRYPTOMATTE_ASSET) != 0) {
     for (short pass = 0; pass < num_passes; pass++) {
       BLI_snprintf_rlen(cryptomatte_pass_name, MAX_NAME, "CryptoAsset%02d", pass);
       RE_engine_register_pass(
-          engine, scene, view_layer, cryptomatte_pass_name, 4, "xyzw", SOCK_RGBA);
+          engine, scene, view_layer, cryptomatte_pass_name, 4, "rgba", SOCK_RGBA);
     }
   }
 }