diff --git a/src/gaussian/formats/cloud_3d.rs b/src/gaussian/formats/cloud_3d.rs
index 819d161d..35feffa1 100644
--- a/src/gaussian/formats/cloud_3d.rs
+++ b/src/gaussian/formats/cloud_3d.rs
@@ -18,10 +18,7 @@ use crate::{
             CommonCloud,
             TestCloud,
         },
-        iter::{
-            PositionIter,
-            PositionParIter,
-        },
+        iter::PositionIter,
         packed::{Gaussian3d, PlanarGaussian3d},
         settings::CloudSettings,
     },
@@ -79,8 +76,8 @@ impl CommonCloud for PlanarGaussian3d {
     }
 
     #[cfg(feature = "sort_rayon")]
-    fn position_par_iter(&self) -> PositionParIter<'_> {
-        PositionParIter::new(&self.position_visibility)
+    fn position_par_iter(&self) -> crate::gaussian::iter::PositionParIter<'_> {
+        crate::gaussian::iter::PositionParIter::new(&self.position_visibility)
     }
 }
 
diff --git a/src/gaussian/formats/cloud_3d_chunked.rs b/src/gaussian/formats/cloud_3d_chunked.rs
new file mode 100644
index 00000000..e69de29b
diff --git a/src/gaussian/formats/cloud_3d_quantized.rs b/src/gaussian/formats/cloud_3d_quantized.rs
new file mode 100644
index 00000000..68a8aaeb
--- /dev/null
+++ b/src/gaussian/formats/cloud_3d_quantized.rs
@@ -0,0 +1,2 @@
+// TODO: gaussian_3d and gaussian_3d_quantized conversions
+// TODO: packed quantized gaussian 3d
diff --git a/src/gaussian/formats/cloud_3d_spz.rs b/src/gaussian/formats/cloud_3d_spz.rs
new file mode 100644
index 00000000..1a69c536
--- /dev/null
+++ b/src/gaussian/formats/cloud_3d_spz.rs
@@ -0,0 +1 @@
+// TODO: spz quantized format https://github.com/nianticlabs/spz
diff --git a/src/gaussian/formats/cloud_4d.rs b/src/gaussian/formats/cloud_4d.rs
index 561a4c45..ad2293b5 100644
--- a/src/gaussian/formats/cloud_4d.rs
+++ b/src/gaussian/formats/cloud_4d.rs
@@ -6,10 +6,7 @@ use crate::{
             CommonCloud,
             TestCloud,
         },
-        iter::{
-            PositionIter,
-            PositionParIter,
-        },
+        iter::PositionIter,
         packed::{Gaussian4d, PlanarGaussian4d},
     },
     random_gaussians_4d,
@@ -182,8 +179,8 @@ impl CommonCloud for PlanarGaussian4d {
     }
 
     #[cfg(feature = "sort_rayon")]
-    fn position_par_iter(&self) -> PositionParIter<'_> {
-        PositionParIter::new(&self.position_visibility)
+    fn position_par_iter(&self) -> crate::gaussian::iter::PositionParIter<'_> {
+        crate::gaussian::iter::PositionParIter::new(&self.position_visibility)
     }
 }
 
diff --git a/src/gaussian/formats/cloud_4d_hierarchy.rs b/src/gaussian/formats/cloud_4d_hierarchy.rs
index 28d6b62d..96671f85 100644
--- a/src/gaussian/formats/cloud_4d_hierarchy.rs
+++ b/src/gaussian/formats/cloud_4d_hierarchy.rs
@@ -1 +1,18 @@
 // TODO: gaussian cloud 4d with temporal hierarchy
+use crate::gaussian::packed::PlanarGaussian4dHandle;
+
+
+pub struct TemporalGaussianLevel {
+    pub instance_count: usize,
+    // TODO: swap buffer slicing
+}
+
+// TODO: make this an asset
+pub struct TemporalGaussianHierarchy {
+    pub flat_cloud: PlanarGaussian4dHandle,
+    pub levels: Vec<TemporalGaussianLevel>,
+    // TODO: level descriptor validation
+}
+
+// TODO: implement level streaming utilities in src/stream/hierarchy.rs
+// TODO: implement GPU slice utilities in src/stream/slice.rs
diff --git a/src/gaussian/formats/cloud_4d_quantized.rs b/src/gaussian/formats/cloud_4d_quantized.rs
new file mode 100644
index 00000000..e69de29b
diff --git a/src/gaussian/formats/mod.rs b/src/gaussian/formats/mod.rs
index d5fac4da..86c3476a 100644
--- a/src/gaussian/formats/mod.rs
+++ b/src/gaussian/formats/mod.rs
@@ -1,2 +1,3 @@
 pub mod cloud_3d;
 pub mod cloud_4d;
+pub mod cloud_4d_hierarchy;
diff --git a/src/gaussian/interface.rs b/src/gaussian/interface.rs
index fddaf6f9..71d66595 100644
--- a/src/gaussian/interface.rs
+++ b/src/gaussian/interface.rs
@@ -7,10 +7,7 @@ use bevy_interleave::prelude::Planar;
 #[cfg(feature = "sort_rayon")]
 use rayon::prelude::*;
 
-use crate::gaussian::iter::{
-    PositionIter,
-    PositionParIter,
-};
+use crate::gaussian::iter::PositionIter;
 
 
 pub trait CommonCloud
@@ -77,7 +74,7 @@ where
     fn position_iter(&self) -> PositionIter<'_>;
 
     #[cfg(feature = "sort_rayon")]
-    fn position_par_iter(&self) -> PositionParIter<'_>;
+    fn position_par_iter(&self) -> crate::gaussian::iter::PositionParIter<'_>;
 }
 
 pub trait TestCloud {