Overview:

Three.js is a powerful JavaScript library that empowers web developers to create stunning 3D graphics and interactive experiences directly in the browser. To harness its potential fully, it's essential to grasp the fundamental concepts that underlie 3D rendering, starting with the 3D coordinate system in Three.js, providing insights and practical examples to helps you navigate to the world of 3D graphics. 

Right-Handed Coordinate System:

Three.js uses a right-handed coordinate system, where the positive X-axis points to the right, the positive Y-axis points up, and the positive Z-axis extends moving away from the viewer and negative values moving towards the viewer.

This system is referred to as “right-handed” because if you extend your right hand and align your thumb with the positive X-axis and your index finger with the positive Y-axis, your middle finger will naturally point along the positive Z-axis.

• Positive X: Points to the right
• Positive Y: Points Upward
• Positive Z: Points away from the viewer or deeper into the screen

The Cartesian Coordinate System:

The foundation of the 3D coordinate system in Three.js is the Cartesian coordinate system. It is mathematical framework used to represent points and positions in three-dimensional space. In this system:

• The X-axis represents the horizontal direction (left to right).
• The Y-axis represents the vertical direction (bottom to top).
• The Z-axis represents the depth of forward-backward direction (front to back)

The Origin (0, 0, 0):

In Three.js as in most 3D environments, the point where all three axes intersect is called the origin. Its coordinates are (0, 0, 0). All other points in the 3D space are defined relative to this origin.

Positive and Negative Directions:

• Positive X values move to the right.
• Negative X values moves to the left.
• Positive Y values move upward.
• Negative Y values move downward.
• Positive Z values move forward into the screen (away from the viewer, deeper into the scene).
• Negative Z values move backward out of the screen (towards the viewer, closer to the screen).

Positioning Objects:

When creating 3D objects in Three.js, you specify their positions using these coordinates. For example, to place a cube 2 units to the right, 3 units upward, and 4 units forward from origin, would set its position to (2, 3, 4).

Transformation Hierarchy:

Understanding the coordinate system is crucial when working with transformation. In Three.js, you can translate (move), rotate, and scale objects. These transformations are applied relative to an object's current position. This hierarchical approach enables the creation of complex animations and arrangements within the 3D scene.

• Translations (moves) change an object's position in the coordinate system.
• Rotations change the orientation of an object.
• Scaling changes an object's size.

Camera Perspective:

The camera's position and orientation also follow the same 3D coordinate system. It determines what part of the 3D scene is visible in the rendering. By changing the camera's position and direction you can control the viewpoint of your 3D scene.