Using UVAtlas (Direct3D 9) 翻译

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于 2022-03-31 19:26:30 首次发布

本文介绍UV Atlas在渲染和内容生成中的应用，讲解其自动创建纹理图集的过程，包括参数设置、控制参数化（如IMT）和处理用户指定折痕。通过实例展示如何使用API减少不连续性和提高效率，最后讨论如何整合到开发流程中以提升模型质量。

Article
06/09/2021
7 minutes to read
7 contributors

Note

UVAtlas was originally shipped in the now-deprecated D3DX9 utilty library. The latest version is available at UV Atlas Command-Line Tool (uvatlas.exe).

笔记

UVAtlas最初是在现已弃用的D3DX9 utilty库中发布的。最新版本可在 UV Atlas Command-Line Tool (uvatlas.exe)中找到。

Many rendering and content generation techniques require a unique, non-overlapping map of a 2D signal (such as a texture) onto a mesh. Such techniques include:

Normal/displacement mapping
Texture-space PRT simulations and light maps
Surface painting
Texture-space lighting

很多的渲染和内容构建技术需要将唯一的、不重叠的2D信号映射到一个网格上（例如2D图片映射到网格上），这样的技术包括：

法线/位移贴图
预处理全局光照贴图和灯光贴图
表面纹理绘制
环境光贴图

Generating a unique UV mapping manually is often time-consuming and tedious; this is especially true when the input geometry is complex and efficient/low-distortion texture-space utilization is desired. The following illustration shows an example mesh and its corresponding texture atlas.

通常手工制作一张uv映射贴图是费时、乏味的，特别是当输入几何体复杂且需要高效/低失真纹理空间利用率时尤其如此，下图显示了一个示例网格及其相应的纹理图集。

This example shows a mesh (on the left) and the corresponding UV-space normal map (on the right). Notice that the texture atlas contains several groups or clusters of data; each cluster is called a chart and in the example above, displays contains the normal data for a portion of the mesh.

这个例子中显示了一个网格（在左边）和相应的uv空间法线贴图（在这右边），注意纹理图集包含了几个数据组或者数据簇；在上面的例子中，每一个簇被叫做一个chart，显示包含部分网格的法线数据。

The D3DX UVAtlas APIs automatically generate an optimal, non-overlapping texture atlas. The APIs provide input parameters that allow you to:

Minimize texture stretch, distortion, and undersampling.
Maximize texture-space packing density for efficient use of memory.
Provide an even sampling across the mesh, minimizing discontinuities in sampling frequency.

D3DX UVAtlas APIs默认使用了一个最优的参数来创建有重叠的纹理图集，APIs允许你设置下面的参数：

最小化纹理拉伸、变形和下采样
最大化纹理空间填充密度，有效利用内存
在整个网格中提供均匀的采样，最大限度地减少采样频率的不连续性。

How UVAtlas Works

The UVAtlas APIs (see UVAtlas Functions) generate a texture atlas by partitioning a surface into charts and packing the charts into a texture atlas. Use D3DXUVAtlasPartition and D3DXUVAtlasPack to perform these steps separately; or use D3DXUVAtlasCreate to partition, parameterize and pack in a single call.