What are Local Coordinate System and Model Coordinate System? Easy-to-understand explanation of the basic concepts of 3D graphics
In the world of 3D graphics, two important concepts come into play when it comes to positioning and manipulating objects: the Local Coordinate System (LCS) and the Model Coordinate System (MCS).
The Local Coordinate System
To understand the Local Coordinate System, imagine a 3D object, such as a cube. The Local Coordinate System of this cube is essentially its own internal system of measurement. It is unique to the object and is not affected by the surrounding environment. The origin of the Local Coordinate System is typically positioned at the center of the object.
When you apply transformations, such as rotations or translations, to the object, these transformations are performed relative to the object’s Local Coordinate System. For example, if you rotate the cube 90 degrees around its vertical axis within its Local Coordinate System, the cube will rotate internally, maintaining its position and orientation relative to itself.
The Model Coordinate System
The Model Coordinate System, on the other hand, represents the position and orientation of objects within the wider 3D world or scene. It acts as a common reference point for all objects in the scene. Each object within the scene has its own Local Coordinate System, but they are all positioned and oriented in relation to the Model Coordinate System.
When you move or rotate an object in the 3D world, these transformations are performed within the Model Coordinate System. The new position and orientation of the object are then calculated based on its Local Coordinate System and its relationship to the Model Coordinate System.
So, in simpler terms, the Model Coordinate System is like a universal framework that all objects in a 3D scene adhere to, while the Local Coordinate System is an internal system unique to each individual object.
Illustrating the Concept
To give a practical example, imagine you have a 3D scene with a car and a house. The car and the house each have their own Local Coordinate Systems, with their origins located at their respective centers. However, when you position the car in the scene, you do so relative to the Model Coordinate System, which acts as the point of reference for the entire scene.
Now, if you were to animate the car to move to a different position, the transformation would be applied based on the Model Coordinate System, impacting the car’s Local Coordinate System which would in turn update its position and orientation relative to the rest of the scene.
In conclusion, understanding the concepts of the Local Coordinate System and the Model Coordinate System is crucial in 3D graphics. It allows us to accurately position and manipulate objects within a 3D scene, creating realistic and visually appealing graphics.
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