The 3D picture we see is actually a computer projection of objects in 3D space from the world coordinate system to the screen coordinate system through a variety of complex calculations, and displayed in the viewport. Say again some simple, equivalent to take a photo of a mobile phone, put the window inside the display.

The objects in life are three-dimensional, but the human eye can only see the front side, not the back side which is blocked. The effect of three-dimensional geometry in the human eye is just like a two-dimensional photograph taken by a camera, what you see is a 2D projection. The process of transforming spatial geometry into a two-dimensional graph is projection, and different projection methods mean different projection size algorithms.

The camera has two main projection modes, one is the orthogonal projection, one is the perspective projection. The following is a brief introduction to Orthogonal Projection Camera and Perspective Projection. For beginners, you should have an impression.

The so-called orthogonal projection, the distance of the object relative to the camera has no effect on the rendering result, that is to say, the object is not far from the camera, rendering the size is the same. This camera is usually used in two-bit games. So an orthogonal projection is also called a parallel projection. Orthogonal projection projects all objects in the scene onto the viewing plane using parallel rays. In an orthogonal projection, the object is the same size as the original object, no matter how far away it is from the eye.

A perspective projection, as it’s called, is a camera that looks more like the real world. The farther away objects are from the camera, the smaller they will be rendered.

Can through the app in ThingJS. Camera. PorjectionType type, set the camera projection reference script as follows:

``/ / Perspective projection app. Camera. ProjectionType = THING. CameraProjectionType. Perspective; / / Orthographic projection app. Camera. ProjectionType = THING. CameraProjectionType. Orthographic;``

If you are looking at the appearance of a digital twin visual scene, the camera is positioned outside the scene. For an indoor roaming preview, place the camera inside a digital twin visualization of a three-dimensional model of the room. — — — — — — — –, digital twin visualization: https://www.thingjs.com/