GLTF模型与包围盒大小的匹配

问题描述

我希望将导入的GLB模型缩放到与场景中的立方体相同的大小。需要确保模型位于阴影投射区域内，并且足够大以使阴影可见。

我已经计算了两个对象的边界框：

// shadowcasting area 
var sceneExtent = new THREE.BoxGeometry( 4, 4, 4 );
var cube = new THREE.Mesh( sceneExtent, material );
var sceneBounds = sceneExtent.computeBoundingBox()

和

// imported mesh
model.traverse( function ( child ) {
    if ( child.isMesh ) {
        child.geometry.computeBoundingBox()
        meshBounds = child.geometry.boundingBox
    }
} );

但现在我不知道如何处理它们来修改GLTF模型的scale

// meshBounds = child.geometry.boundingBox
// sceneBounds = sceneExtent.computeBoundingBox()

// how to resize model scale to match size of sceneBounds

model.scale.set(1,1,1)

我已经研究了很多，但到目前为止我似乎还不明白我找到的解决方案。

如何修改模型比例以使sceneBounds与我已有的信息相匹配？

更新：若要获取边界框，请改用.setFromObject()：

sceneBounds = new THREE.Box3().setFromObject( cube );
meshBounds = new THREE.Box3().setFromObject( model );

推荐答案

例如：

// Calculate side lengths of scene (cube) bounding box
let lengthSceneBounds = {
  x: Math.abs(sceneBounds.max.x - sceneBounds.min.x),
  y: Math.abs(sceneBounds.max.y - sceneBounds.min.y),
  z: Math.abs(sceneBounds.max.z - sceneBounds.min.z),
};

// Calculate side lengths of glb-model bounding box
let lengthMeshBounds = {
  x: Math.abs(meshBounds.max.x - meshBounds.min.x),
  y: Math.abs(meshBounds.max.y - meshBounds.min.y),
  z: Math.abs(meshBounds.max.z - meshBounds.min.z),
};

// Calculate length ratios
let lengthRatios = [
  (lengthSceneBounds.x / lengthMeshBounds.x),
  (lengthSceneBounds.y / lengthMeshBounds.y),
  (lengthSceneBounds.z / lengthMeshBounds.z),
];

// Select smallest ratio in order to contain the model within the scene
let minRatio = Math.min(...lengthRatios);

// If you need some padding on the sides
let padding = 0;
minRatio -= padding;

// Use smallest ratio to scale the model
model.scale.set(minRatio, minRatio, minRatio);

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