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

1 files changed, 6 insertions, 6 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);