Three js

Three.js is a cross-browser open source JavaScript library and application programming interface (API) used to create and display animated 3D and 2D computer graphics in a web browser using WebGL. The source code is hosted in a repository on GitHub.
It uses WebGL API behind the scene.  Three.js allow you to use your GPU(Graphics Processing Unit) to render the Graphics and 3D objects on a canvas in the web browser. since we are using JavaScript so we can also interact with other HTML elements. 

Since Three.js is open source we can easily watch the source code and understand the functionality of the code(functions).
It doesn’t required any third party plugin to run the code.
You just need to work on only one programming language JavaScript and off course HTML.

You can download a zip file with the three js code clicking on download or going to https://threejs.org/

Features

- Effects: Anaglyph, cross-eyed, and parallax barrier.
- Scenes: add and remove objects at run-time; fog
- Cameras: perspective and orthographic; controllers: trackball, FPS, path and more
- Animation: armatures, forward kinematics, inverse kinematics, morph, and keyframe
- Lights: ambient, direction, point, and spot lights; shadows: cast and receive
- Materials: Lambert, Phong, smooth shading, textures, and more
- Shaders: access to full OpenGL Shading Language (GLSL) capabilities: lens flare, depth pass, and extensive post-processing library
- Objects: meshes, particles, sprites, lines, ribbons, bones, and more - all with Level of detail
- Geometry: plane, cube, sphere, torus, 3D text, and more; modifiers: lathe, extrude, and tube
- Data loaders: binary, image, JSON, and scene
-Utilities: full set of time and 3D math functions including frustum, matrix, quaternion, UVs, and more
- Export and import: utilities to create Three.js-compatible JSON files from within: Blender, openCTM, FBX, Max, and OBJ
- Support: API documentation is under construction. A public forum and wiki is in full operation.
- Examples: Over 150 files of coding examples plus fonts, models, textures, sounds, and other support files
- Debugging: Stats.js,[14] WebGL Inspector, Three.js Inspector
- Virtual and Augmented Reality via WebXR
- Three.js runs in all browsers supported by WebGL 1.0.

Three.js is made available under the MIT License.