BufferGeometry偏移量和索引 [英] BufferGeometry offsets and indices

问题描述

我只想知道一段时间究竟是什么抵消和指数/指数。偏移是例如在 https://github.com/mrdoob/three中提到IndexedGeometry中提到了.js / blob / dev / src / core / BufferGeometry.js 和索引，但我现在无法在开发树中找到它。
虽然指数看起来相当明显，虽然我可以深入研究代码，为自己找出一些可能正确的答案，我很乐意听到官方陈述：）

I was just wondering for a while now what exactly "offsets" and "indices / index" are. Offsets are e.g. mentioned in https://github.com/mrdoob/three.js/blob/dev/src/core/BufferGeometry.js and indices were mentioned in IndexedGeometry, however I can't currently find it anymore in the dev tree. Although indices seem rather obvious and although I could dive into the code to figure out some maybe-correct answer for myself I'd love to hear an "official" statement :)

谢谢！

推荐答案

定义几何有两种方法：

非索引

"vertices": [ 0, 1, 2,  3, 4, 5,  6, 7, 8,  ... ],
"normals":  [ 0, 1, 2,  3, 4, 5,  6, 7, 8,  ... ]

在此模式下，每个三角形位置都是定义的，您无法重复使用数据。

In this mode every triangle position is as defined and you can't reuse data.

triangle 0: [ 0, 1, 2,  3, 4, 5,  6, 7, 8 ]

已编入索引

"indices":  [ 0, 1, 2, ... ],
"vertices": [ 0, 1, 2,  3, 4, 5,  6, 7, 8,  ... ],
"normals":  [ 0, 1, 2,  3, 4, 5,  6, 7, 8,  ... ]

在此模式下，索引定义数据的顺序。第一个三角形是使用索引 0 ， 1 ， 2 。这些索引将用于获取顶点和法线数据：

In this mode, indices define the order of the data. The first triangle is using indices 0, 1, and 2. These indices will be used to fetch the vertices and normals data:

triangle 0: [ 0, 1, 2,  3, 4, 5,  6, 7, 8 ]

索引的主要好处是可以重用数据并将较少的数据上传到GPU：

The main benefit of indexed is the possibility of reusing data and uploading less data to the GPU:

"indices":  [ 0, 0, 0, ... ],
"vertices": [ 0, 1, 2,  3, 4, 5,  6, 7, 8,  ... ]

triangle 0: [ 0, 1, 2,  0, 1, 2,  0, 1, 2 ]

根据抵消 ...

借助抵消，您可以渲染特定的范围几何。而不是从三角形0 到 triangle.length ，您可以从三角形200 到三角形400 。

With offsets you can render specific ranges of your geometry. Instead of drawing from triangle 0 to triangle.length, you can draw from triangle 200 to triangle 400.

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