So far, we've explored some of the fundamental building blocks of 3D scenes in Three.js: geometries and materials. We've seen how to use built-in geometries like spheres and cubes and how to apply basic materials to give them color and texture. However, the real magic of 3D creation often lies in crafting unique shapes that don't exist in standard libraries. This is where custom geometries come into play.
Creating custom geometries in Three.js involves defining the vertices (points in 3D space) and faces (the polygons that connect these vertices) that make up your desired shape. While it might sound complex, it's a powerful technique that unlocks endless possibilities for your creative projects. Think of it as drawing in 3D space by meticulously placing every point and connecting them to form surfaces.
In this section, we'll introduce the core concepts behind creating custom geometries. We'll start by understanding how Three.js represents these shapes and then delve into the essential components you'll need to define your own. This will lay the groundwork for building everything from simple custom shapes to intricate, organic forms.
At its heart, a custom geometry in Three.js is defined by two main pieces of information:
- Vertices: These are the individual points that define the corners or key locations of your shape in 3D space. Each vertex is represented by its X, Y, and Z coordinates.
- Faces (or Indices): These define how the vertices are connected to form polygons (usually triangles or quads) that make up the surface of your geometry. By specifying which vertices form each face, you create the actual shape.
Three.js provides a BufferGeometry class, which is the modern and most efficient way to handle geometry data. Instead of defining vertices and faces separately in a way that might be less performant, BufferGeometry uses typed arrays (like Float32Array and Uint32Array) to store attributes like vertex positions, normals, UV coordinates, and more. This approach offers significant performance advantages, especially for complex geometries.