There are two main ways of representing 3D objects, BRep and mesh.
BRep is the equivalent of a vector image. It has the advantage of having the notions of faces and edges within the representation. This is what replicad uses.
Meshes is the equivalent of a raster image. This is how 3D art is usually made. It has some performance advantages. This is what JSCAD uses.
The reason the example took some time to load is that the code needed to get to the page a first time. After this it is snappy everywhere.
BRep is the equivalent of a vector image. It has the advantage of having the notions of faces and edges within the representation. This is what replicad uses.
Meshes is the equivalent of a raster image. This is how 3D art is usually made. It has some performance advantages. This is what JSCAD uses.
The reason the example took some time to load is that the code needed to get to the page a first time. After this it is snappy everywhere.