Fix T84878: Eevee cryptomatte broken with stereoscopy

During multiview rendering the `cryptomatte_accum_buffer` is not cleared
between the views and leaves artifacts on the next view to be rendered.
This change clears the accum buffer when it already exists and will be
reused for the next view.

1 files changed, 8 insertions, 0 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_cryptomatte.c b/source/blender/draw/engines/eevee/eevee_cryptomatte.c
index 91a230e987c..90948d67895 100644
--- a/source/blender/draw/engines/eevee/eevee_cryptomatte.c
+++ b/source/blender/draw/engines/eevee/eevee_cryptomatte.c
@@ -161,6 +161,14 @@ void EEVEE_cryptomatte_output_init(EEVEE_ViewLayerData *UNUSED(sldata),
     g_data->cryptomatte_download_buffer = MEM_malloc_arrayN(
         sizeof(float), buffer_size * num_cryptomatte_layers, __func__);
   }
+  else {
+    /* During multiview rendering the `cryptomatte_accum_buffer` is deallocated after all views
+     * have been rendered. Clear it here to be reused by the next view. */
+    memset(g_data->cryptomatte_accum_buffer,
+           0,
+           buffer_size * eevee_cryptomatte_pixel_stride(view_layer) *
+               sizeof(EEVEE_CryptomatteSample));
+  }
 
   DRW_texture_ensure_fullscreen_2d(&txl->cryptomatte, format, 0);
   GPU_framebuffer_ensure_config(&fbl->cryptomatte_fb,