my zoom is not clear

I have a task which is about Cesium. I created buttons to zoom to particular countries… However, when i clicked the button,Singapore it zooms to Singapore but however the zoom is not perfect.Let me show you an image when i clicked the button Singapore. I want a better image just like the last one.

My Work @import url(../Build/Cesium/Widgets/widgets.css); html, body, #cesiumContainer { width: 98%; height: 98%; margin: 0; padding: 0; overflow: hidden; }

Zoom To Singapore

Zoom To Malaysia

My question, if i click Singapore, it will zoom to Singapore just like the second image which i have attached to this question… Can you please help me?? Thank you