Don't ignore unbatchable sorted items. (#13144)

In #12889, I mistakenly started dropping unbatchable sorted items on the
floor instead of giving them solitary batches. This caused the objects
in the `shader_instancing` demo to stop showing up. This patch fixes the
issue by giving those items their own batches as expected.

Fixes #13130.

crates/bevy_render/src/batching/gpu_preprocessing.rs

@@ -303,7 +303,9 @@ where
 
  /// Metadata that can be used to determine whether an instance can be placed
  /// into this batch.
- meta: BatchMeta<F::CompareData>,
+ ///
+ /// If `None`, the item inside is unbatchable.
+ meta: Option<BatchMeta<F::CompareData>>,
 }
 
 impl<F> SortedRenderBatch<F>
@@ -405,29 +407,22 @@ pub fn batch_and_prepare_sorted_render_phase<I, GFBD>(
 
  // Unpack that index and metadata. Note that it's possible for index
  // and/or metadata to not be present, which signifies that this
- // entity is unbatchable. In that case, we break the batch here and
- // otherwise ignore the phase item.
- let (current_input_index, current_meta);
- match current_batch_input_index {
- Some((input_index, Some(current_compare_data))) => {
- current_input_index = Some(input_index);
- current_meta = Some(BatchMeta::new(
- &phase.items[current_index],
- current_compare_data,
- ));
- }
- _ => {
- current_input_index = None;
- current_meta = None;
- }
+ // entity is unbatchable. In that case, we break the batch here.
+ let (mut current_input_index, mut current_meta) = (None, None);
+ if let Some((input_index, maybe_meta)) = current_batch_input_index {
+ current_input_index = Some(input_index);
+ current_meta =
+ maybe_meta.map(|meta| BatchMeta::new(&phase.items[current_index], meta));
  }
 
  // Determine if this entity can be included in the batch we're
  // building up.
  let can_batch = batch.as_ref().is_some_and(|batch| {
- current_meta
- .as_ref()
- .is_some_and(|current_meta| batch.meta == *current_meta)
+ // `None` for metadata indicates that the items are unbatchable.
+ match (&current_meta, &batch.meta) {
+ (Some(current_meta), Some(batch_meta)) => current_meta == batch_meta,
+ (_, _) => false,
+ }
  });
 
  // Make space in the data buffer for this instance.
@@ -442,23 +437,21 @@ pub fn batch_and_prepare_sorted_render_phase<I, GFBD>(
  }
 
  // Start a new batch.
- batch = current_meta.map(|meta| {
- let indirect_parameters_index = if gpu_culling {
- GFBD::get_batch_indirect_parameters_index(
- &system_param_item,
- &mut indirect_parameters_buffer,
- current_entity,
- output_index,
- )
- } else {
- None
- };
- SortedRenderBatch {
- phase_item_start_index: current_index as u32,
- instance_start_index: output_index,
- indirect_parameters_index,
- meta,
- }
+ let indirect_parameters_index = if gpu_culling {
+ GFBD::get_batch_indirect_parameters_index(
+ &system_param_item,
+ &mut indirect_parameters_buffer,
+ current_entity,
+ output_index,
+ )
+ } else {
+ None
+ };
+ batch = Some(SortedRenderBatch {
+ phase_item_start_index: current_index as u32,
+ instance_start_index: output_index,
+ indirect_parameters_index,
+ meta: current_meta,
  });
  }