如何用pycollada创建含多长方体的Collada文件及核心变量解析

Let's break down each of these arrays step by step—they’re all critical for defining a cube’s 3D geometry in the Collada format, which relies on structured vertex data to render shapes.

What is vert_floats? #

vert_floats stores the 3D coordinates of the cube’s vertices (its 8 corner points).

• Each set of 3 consecutive floats represents a single vertex’s (X, Y, Z) position in 3D space.
• A cube has exactly 8 unique corners, so 8 vertices × 3 coordinates per vertex = 24 elements total.
• For example:
  • The first 3 elements (-50,50,50) are the coordinates of the cube’s top-front-left corner
  • The next 3 (50,50,50) are the top-front-right corner, and so on for all 8 corners.

What is normal_floats? #

normal_floats holds surface normal vectors—these are 3D vectors pointing perpendicular to each face, used for calculating how light interacts with the cube.

• Each set of 3 consecutive floats is a normal vector’s (X, Y, Z) direction.
• The cube has 6 flat faces, and every vertex on a single face uses the same normal (since the face is flat). Each face has 4 vertices, so we repeat the face’s normal 4 times.
• That’s 6 faces × 4 vertices per face × 3 values per normal = 72 elements total.
• For example:
  • The first 12 elements (0,0,1 repeated 4 times) are normals for the front face (pointing along the positive Z-axis)
  • The next 12 (0,1,0 repeated 4 times) are normals for the top face (pointing along the positive Y-axis), and so on for the back, bottom, left, and right faces.

What is indices? #

The indices array acts as a lookup table to combine vertices and normals into the triangles that make up the cube’s faces (most 3D renderers use triangles to render polygons).

• Each pair of numbers represents a "vertex instance": the first number is an index into vert_floats (divide by 3 to get the actual vertex), and the second is an index into normal_floats (divide by 3 to get the actual normal).
• A cube’s 6 square faces are each split into 2 triangles (since squares aren’t directly renderable in most pipelines), giving 12 triangles total. Each triangle needs 3 vertex instances, so 12 triangles × 3 instances × 2 values per instance = 72 elements total.
• For example, the first 6 elements (0,0,2,1,3,2) define the first triangle of the front face:
  • Uses vertex index 0 (-50,50,50) with normal index 0 (0,0,1)
  • Uses vertex index 2 (-50,-50,50) with normal index 1 (0,0,1)
  • Uses vertex index 3 (50,-50,50) with normal index 2 (0,0,1)

内容的提问来源于stack exchange，提问作者Vivek Bagaria