adjust model size

app/home-modle.tsx

@@ -1,11 +1,12 @@
 'use client';
 
-import { Canvas, useFrame, useLoader } from '@react-three/fiber';
-import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader';
-import { DRACOLoader } from 'three/examples/jsm/loaders/DRACOLoader';
-import { Environment, OrbitControls, useProgress } from '@react-three/drei';
-import { useRef, useState } from 'react';
+import { useProgress } from '@react-three/drei';
+import { Canvas, useFrame, useLoader, useThree } from '@react-three/fiber';
+import { frameArea } from 'lib/utils';
+import { useRef } from 'react';
 import * as THREE from 'three';
+import { DRACOLoader } from 'three/examples/jsm/loaders/DRACOLoader';
+import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader';
 
 const Model = () => {
   const mixer = useRef<THREE.AnimationMixer | null>(null);
@@ -19,16 +20,27 @@ const Model = () => {
     }
   );
 
-  const [loading, setLoading] = useState(true);
-  useProgress((state) => {
-    if (state.progress >= 100) {
-      mixer.current = new THREE.AnimationMixer(gltf.scene);
-      gltf.animations.forEach((clip) => {
-        mixer.current?.clipAction(clip).play();
-      });
-      setLoading(false);
-    }
+  const camera = useThree((state) => state.camera);
+  const process = useProgress((state) => {
+    if (state.progress < 100) return state.progress;
 
+    // After model loaded.
+    mixer.current = new THREE.AnimationMixer(gltf.scene);
+    gltf.animations.forEach((clip) => {
+      mixer.current?.clipAction(clip).play();
+    });
+
+    const box = new THREE.Box3().setFromObject(gltf.scene);
+    const boxSize = box.getSize(new THREE.Vector3()).length();
+    const boxCenter = box.getCenter(new THREE.Vector3());
+    frameArea(
+      boxSize * 0.8,
+      boxSize,
+      boxCenter,
+      camera as THREE.PerspectiveCamera
+    );
+    camera.position.z += 0.15;
+    camera.position.y -= 0.15;
     return state.progress;
   });
 
@@ -46,13 +58,9 @@ const Model = () => {
 const HomeModel = () => {
   return (
     <Canvas>
-      <spotLight color={0xffffff} intensity={2} distance={100} angle={15} />
-      <ambientLight color={0xffffff} intensity={1} />
+      <spotLight color={0xffffff} intensity={1.5} distance={100} angle={15} />
+      <ambientLight color={0xffffff} intensity={0.5} />
       <Model />
-      {/*
-      <OrbitControls />
-      <Environment preset="sunset" background />
-          */}
     </Canvas>
   );
 };

lib/utils/index.ts

@@ -1,3 +1,5 @@
+import * as THREE from 'three';
+
 export const sortByDate = (
   { date: a }: { date: string },
   { date: b }: { date: string }
@@ -118,3 +120,34 @@ export const debounce: Debounce = (fn, ms) => {
     }, ms);
   };
 };
+
+export const frameArea = (
+  sizeToFitOnScreen: number,
+  boxSize: number,
+  boxCenter: THREE.Vector3,
+  camera: THREE.PerspectiveCamera
+) => {
+  const halfSizeToFitOnScreen = sizeToFitOnScreen * 0.5;
+  const halfFovY = THREE.MathUtils.degToRad(camera.fov * 0.5);
+  const distance = halfSizeToFitOnScreen / Math.tan(halfFovY);
+  // compute a unit vector that points in the direction the camera is now
+  // in the xz plane from the center of the box
+  const direction = new THREE.Vector3()
+    .subVectors(camera.position, boxCenter)
+    .multiply(new THREE.Vector3(1, 0, 1))
+    .normalize();
+
+  // move the camera to a position distance units way from the center
+  // in whatever direction the camera was from the center already
+  camera.position.copy(direction.multiplyScalar(distance).add(boxCenter));
+
+  // pick some near and far values for the frustum that
+  // will contain the box.
+  camera.near = boxSize / 100;
+  camera.far = boxSize * 100;
+
+  camera.updateProjectionMatrix();
+
+  // point the camera to look at the center of the box
+  camera.lookAt(boxCenter.x, boxCenter.y, boxCenter.z);
+};