1 files changed, 15 insertions, 0 deletions
diff --git a/intern/cycles/kernel/film/read.h b/intern/cycles/kernel/film/read.h
index 18a593a75b1..ba895fd8909 100644
--- a/intern/cycles/kernel/film/read.h
+++ b/intern/cycles/kernel/film/read.h
@@ -214,6 +214,21 @@ ccl_device_inline void film_get_pass_pixel_light_path(
   pixel[0] = f.x;
   pixel[1] = f.y;
   pixel[2] = f.z;
+
+  /* Optional alpha channel. */
+  if (kfilm_convert->num_components >= 4) {
+    if (kfilm_convert->pass_combined != PASS_UNUSED) {
+      float scale, scale_exposure;
+      film_get_scale_and_scale_exposure(kfilm_convert, buffer, &scale, &scale_exposure);
+
+      ccl_global const float *in_combined = buffer + kfilm_convert->pass_combined;
+      const float alpha = in_combined[3] * scale;
+      pixel[3] = film_transparency_to_alpha(alpha);
+    }
+    else {
+      pixel[3] = 1.0f;
+    }
+  }
 }
 
 ccl_device_inline void film_get_pass_pixel_float3(ccl_global const KernelFilmConvert *ccl_restrict