The simplest techniques for 3D rendering without relying on a GPU and WebGL are indeed (2.5D) raycasting engines (such as this Voxel Space engine). A short goog

The simplest techniques for 3D rendering without relying on a GPU and WebGL are indeed (2.5D) raycasting engines (such as this Voxel Space engine). A short google search reveals for example: http://www.playfuljs.com/a-first-person-engine-in-265-lines/ http://www.playfuljs.com/a-first-person-engine-in-265-lines/ Also read the readme file of this Voxel Space engine. Maybe this is already enough to understand the principle.