From ba0b28d61658676deaecdbf91cbcbeeb9079ba39 Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Tue, 31 Mar 2026 17:39:39 +0200
Subject: [PATCH] Add model instance rendering functionality

---
 src/assets/model-instance-rendering.ts | 104 +++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 src/assets/model-instance-rendering.ts

diff --git a/src/assets/model-instance-rendering.ts b/src/assets/model-instance-rendering.ts
new file mode 100644
index 00000000..15d2b533
--- /dev/null
+++ b/src/assets/model-instance-rendering.ts
@@ -0,0 +1,104 @@
+import { BoxGeometry, Group, Mesh, MeshBasicMaterial } from "three";
+
+import type { Vec3 } from "../core/vector";
+
+import { instantiateModelTemplate, type LoadedModelAsset } from "./gltf-model-import";
+import type { ModelInstance } from "./model-instances";
+import type { ProjectAssetRecord } from "./project-assets";
+
+const MODEL_PLACEHOLDER_COLOR = 0x89b6ff;
+const MODEL_SELECTION_COLOR = 0xf7d2aa;
+
+interface ModelInstanceBounds {
+  center: Vec3;
+  size: Vec3;
+}
+
+function cloneVec3(vector: Vec3): Vec3 {
+  return {
+    x: vector.x,
+    y: vector.y,
+    z: vector.z
+  };
+}
+
+function getLocalModelBounds(asset: ProjectAssetRecord | undefined): ModelInstanceBounds {
+  if (asset?.kind === "model" && asset.metadata.boundingBox !== null) {
+    const boundingBox = asset.metadata.boundingBox;
+
+    return {
+      center: {
+        x: (boundingBox.min.x + boundingBox.max.x) * 0.5,
+        y: (boundingBox.min.y + boundingBox.max.y) * 0.5,
+        z: (boundingBox.min.z + boundingBox.max.z) * 0.5
+      },
+      size: {
+        x: Math.max(0.1, Math.abs(boundingBox.max.x - boundingBox.min.x)),
+        y: Math.max(0.1, Math.abs(boundingBox.max.y - boundingBox.min.y)),
+        z: Math.max(0.1, Math.abs(boundingBox.max.z - boundingBox.min.z))
+      }
+    };
+  }
+
+  return {
+    center: {
+      x: 0,
+      y: 0,
+      z: 0
+    },
+    size: {
+      x: 1,
+      y: 1,
+      z: 1
+    }
+  };
+}
+
+function createWireframeBox(size: Vec3, color: number, opacity: number): Mesh {
+  return new Mesh(
+    new BoxGeometry(size.x, size.y, size.z),
+    new MeshBasicMaterial({
+      color,
+      wireframe: true,
+      transparent: true,
+      opacity,
+      depthWrite: false
+    })
+  );
+}
+
+export function createModelInstanceRenderGroup(
+  modelInstance: ModelInstance,
+  asset: ProjectAssetRecord | undefined,
+  loadedAsset: LoadedModelAsset | undefined,
+  selected = false
+): Group {
+  const bounds = getLocalModelBounds(asset);
+  const group = new Group();
+
+  group.position.copy(cloneVec3(modelInstance.position));
+  group.rotation.set(
+    (modelInstance.rotationDegrees.x * Math.PI) / 180,
+    (modelInstance.rotationDegrees.y * Math.PI) / 180,
+    (modelInstance.rotationDegrees.z * Math.PI) / 180
+  );
+  group.scale.set(modelInstance.scale.x, modelInstance.scale.y, modelInstance.scale.z);
+  group.userData.modelInstanceId = modelInstance.id;
+  group.userData.assetId = modelInstance.assetId;
+
+  if (loadedAsset !== undefined) {
+    group.add(instantiateModelTemplate(loadedAsset.template));
+  } else {
+    const placeholder = createWireframeBox(bounds.size, MODEL_PLACEHOLDER_COLOR, 0.28);
+    placeholder.position.set(bounds.center.x, bounds.center.y, bounds.center.z);
+    group.add(placeholder);
+  }
+
+  if (selected) {
+    const selectionShell = createWireframeBox(bounds.size, MODEL_SELECTION_COLOR, 0.8);
+    selectionShell.position.set(bounds.center.x, bounds.center.y, bounds.center.z);
+    group.add(selectionShell);
+  }
+
+  return group;
+}