# 3D-Tiles ModelMatrix does not work for region??

**URL:** <https://community.cesium.com/t/3d-tiles-modelmatrix-does-not-work-for-region/5518>\
**Category:** CesiumJS\
**Created:** [May 14, 2017, 3:20pm UTC](https://community.cesium.com/t/3d-tiles-modelmatrix-does-not-work-for-region/5518 "2017-05-14T15:20:05Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![FKAss](https://avatars.discourse-cdn.com/v4/letter/f/958977/32.png) [@FKAss](https://community.cesium.com/u/FKAss)\
**Post date:** [May 14, 2017, 3:20pm UTC](https://community.cesium.com/t/3d-tiles-modelmatrix-does-not-work-for-region/5518/1 "2017-05-14T15:20:05Z")

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hi,everyone ,i use cesium3DTile to load my data, code like this:

this.modelLayer = new Cesium.Cesium3DTileset({  
name: “倾斜三维模型”,  
url: modelTileSet,  
modelMatrix:posMat  
});

modelMatrix works fine for tiles that boundingVolume defined by sphere, model tile is transformed , but when i change my data which boundingVolume defined by region ,modelMatrix does not work.

i view source code of Cesium3DTile.js, find the createBoundingVolume function, about line 842: i wonder why boundingVolumeHeader.region Don’t update regions when the transform changes

Cesium3DTile.prototype.createBoundingVolume = …  
else if (defined(boundingVolumeHeader.region)) {  
var region = boundingVolumeHeader.region;  
var rectangleRegion = Rectangle.unpack(region, 0, scratchRectangle);  
if (defined(result)) {  
**// Don’t update regions when the transform changes**  
return result;  
}

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<div class="post-metadata">

**Author:** ![sean\_lilley](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/sean_lilley/32/2083_2.png) [@sean\_lilley](https://community.cesium.com/u/sean_lilley)\
**Post date:** [May 15, 2017, 10:57pm UTC](https://community.cesium.com/t/3d-tiles-modelmatrix-does-not-work-for-region/5518/2 "2017-05-15T22:57:24Z")

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The transform still applies to the contents of the tile, but just not to the region bounding volume itself. Conceptually since region is specified in cartographic coordinates and the transform is specified in cartesian coordinates it doesn’t really make sense that a region could be transformed.