Don't disable OIT if SSAO is off

Author: adamchalmers

rust/kcl-lib/src/engine/mod.rs

@@ -234,12 +234,6 @@ pub trait EngineManager: std::fmt::Debug + Send + Sync + 'static {
             &ModelingCmd::SceneClearAll(mcmd::SceneClearAll::default()),
         )
         .await?;
-        self.batch_modeling_cmd(
-            id_generator.next_uuid(),
-            source_range,
-            &ModelingCmd::from(mcmd::SetOrderIndependentTransparency::builder().enabled(false).build()),
-        )
-        .await?;
 
         // Flush the batch queue, so clear is run right away.
         // Otherwise the hooks below won't work.

rust/kcl-lib/src/execution/mod.rs

@@ -791,7 +791,19 @@ impl ExecutorContext {
 
         self.engine
             .clear_scene(&mut exec_state.mod_local.id_generator, source_range)
-            .await
+            .await?;
+        // The engine errors out if you toggle OIT with SSAO off.
+        // So ignore OIT settings if SSAO is off.
+        if self.settings.enable_ssao {
+            self.engine
+                .batch_modeling_cmd(
+                    exec_state.mod_local.id_generator.next_uuid(),
+                    source_range,
+                    &ModelingCmd::from(mcmd::SetOrderIndependentTransparency::builder().enabled(false).build()),
+                )
+                .await?;
+        }
+        Ok(())
     }
 
     pub async fn bust_cache_and_reset_scene(&self) -> Result<ExecOutcome, KclErrorWithOutputs> {

rust/kcl-lib/src/std/appearance.rs

@@ -123,8 +123,13 @@ async fn inner_appearance(
         }
     }
 
+    // OIT (order-independent transparency) is required to show transparency.
+    // But it degrades engine performance. So only enable it if necessary,
+    // i.e. if user has chosen to make something transparent.
     let mut needs_oit = false;
     let opacity_param = if let Some(opacity) = opacity {
+        // The engine errors out if you toggle OIT with SSAO off.
+        // So ignore OIT settings if SSAO is off.
         if opacity < 100.0 && args.ctx.settings.enable_ssao {
             needs_oit = true;
         }