深度渲染纹理格式。
Depth format is used to render high precision "depth" value into a render texture. Which format
is actually used depends on platform support and on the number of depth bits you request through the constructor.
You can also set an exact depth-stencil format with RenderTexture.depthStencilFormat or a
RenderTexture constructor that takes GraphicsFormat. Use SystemInfo.IsFormatSupported to check your platform supports this.
When writing
shaders that use or render into a depth texture, care must be taken to ensure that they work both
on OpenGL and on Direct3D, see depth textures documentation.
请注意，并非所有显卡都支持深度纹理。请使用 SystemInfo.SupportsRenderTextureFormat
检查支持情况。
Additional resources: RenderTexture class, SystemInfo.SupportsRenderTextureFormat.