As the camera is being moved, why doesn’t the ModelViewMatrix change?

Sorry, your question is unclear because the Camera class does not have a property modelViewMatrix .

I meant Object3D.modelviewmatrix. Object3D is the grandparent of the orthographic camera.

Okay. Well, the matrix is only necessary for the shader so it’s only recomputed right before rendering.

Notice that the matrix is only computed for renderable objects. Not cameras.

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I appreciate the quick response. The following is the definition I normally see used to define the modelview matrix: ModelView matrix is the concatenation of model matrix and view Matrix. View Matrix defines the position(location and orientation) of the camera, while model matrix defines the frame’s position of the primitives you are going to draw.

Does THREEJS have a matrix that corresponds to the definition provided above?

I don’t think these are proper definitions. A model matrix represents the world transformation of a 3D object (so it transforms from local/model to world space). The view matrix is the inverse world matrix of the camera and transforms an object from world space into camera/view/eye space. By concatenating both matrices, you can directly transform from the model’s local space to view space.