HDRI

人类发展研究所

Introduction

引言

What exactly are HDRIs (High-Dynamic Range Images)?

什么是高动态范围图像？

HDRIs are ideal for use in combination with GI and to recreate very natural and realistic lighting situations. HDRIs also have a big impact on the realism of reflections because they can produce reflections on objects that are much brighter than reflections caused by normal textures.

HDRIs 是理想的结合使用与 GI 和重建非常自然和现实的照明情况。高分辨率反射镜也对反射的真实感有很大的影响，因为它们可以产生对物体的反射，这些物体比普通纹理产生的反射要明亮得多。

In short, HDRIs are images with a very high brightness range, much higher than normal RGB images, which are limited to a brightness range of 8 bits (256 variations) per color.

简而言之，高清晰度图像是一个非常高的亮度范围，远高于正常的 RGB 图像，其亮度范围限制在8位(256变化)每种颜色。

Standard RGB images have the limitation of the brightest possible color being a 255/255/255 white. If you use such an image in combination with GI to illuminate a scene, even the brightest white will not be bright enough to simulate a real lighting situation. The resulting renderings often look flat and lack contrast. That’s because in reality the difference between a dark light (e.g., candle flame) and a bright light (e.g., sun) is too big to be represented within an 8-bit RGB image.

标准的 RGB 图像最亮的颜色是255/255/255白色。如果你使用这样的图像与 GI 结合来照亮一个场景，即使是最亮的白色也不足以模拟真实的照明情况。由此产生的渲染效果往往看起来平淡，缺乏对比度。这是因为在现实中，暗光(如蜡烛火焰)和亮光(如太阳)之间的差异太大，无法用8位 RGB 图像来表示。

However, using a HDRI, the sun could have a brightness value of, say, 6000% that is taken into account by the GI algorithm and when rendering reflections. This results in beautifully and realistically illuminated scenes.

然而，使用 HDRI，太阳的亮度值可以达到6000% ，这是 GI 算法和渲染反射时要考虑的。这样就形成了美丽而逼真的场景。

The following pictures illustrate the tremendous difference that HDRIs can make (all HDRI © Paul Debevec):

下面的图片说明了 HDRIs 可以带来的巨大差异(所有 HDRI Paul Debevec) :

Without HDRI. 没有 HDRI

With HDRI. 使用 HDRI

Try re-rendering your old scenes with HDRI. You will be surprised by how much of a difference HDRIs can make!

尝试使用 HDRI 重新渲染你的旧场景。你会惊讶于 HDRI 能带来多大的改变！

Types of HDRI

高血压病种类

There are three main types of HDRI:

有三种主要类型的多边债务减免:

HDRI Latitude/Longitude 经度/纬度

These images are distorted in such a way that they can be mapped onto a sphere (or a Sky object) using spherical mapping which produces perfect results.

这些图像以这样一种方式被扭曲，他们可以被映射到一个球体(或天空对象)使用球形映射产生完美的结果。

This type of HDRI works best in Cinema 4D. Other types of HDRI can be converted to this projection type as described later in this chapter.

这种类型的 HDRI 在C4D中效果最好。其他类型的 HDRI 可以转换为这种投影类型，如本章后面所述。

HDRI Light Probes HDRI 光探针

These HDRIs are generated by taking pictures of a reflective sphere.

这些高分辨率数字显示器是通过拍摄一个反射球而产生的。

HDRI Horizontal/Vertical Cross. 水平/垂直交叉

These HDRIs are laid out like an unfolded cube and are designed to be mapped onto a cube that surrounds the scene. In Cinema 4D, however, we recommend using the Latitude/Longitude type instead.

这些 hdri 的布局就像一个没有折叠的立方体，被设计成映射到场景周围的立方体上。然而，在 Cinema 4D 中，我们建议使用纬度/经度类型来代替。

Usage

用法

HDRIs can be used as textures in the Color channel or Luminance channel of materials. When using a Sky object, you can use it in either of these channels. For spheres used as environments you must use the Luminance channels.

Hdri 可以用作材质的颜色通道或亮度通道。当使用 Sky 对象时，您可以在这两个通道中的任何一个中使用它。对于用作环境的球体，必须使用亮度通道。

Depending on the intensity of the HDRI texture, the scene may be too dark or too bright. You can adjust the HDRI brightness in the following ways:

根据 HDRI 纹理的强度，场景可能太暗或太亮。你可以通过以下方式调整 HDRI 亮度:

Using the 使用Intensity, Gamma 强度，伽玛 parameter in the render settings (GI page) and the Global Illumination Generate/Receive options on the Illumination page of the material that uses the HDRI texture. 参数的渲染设置(GI 页面)和全局光源生成/接收选项的照明页面的材质，使用 HDRI 纹理

or by directly changing the brightness of the HDRI texture:

或者直接改变 HDRI 纹理的亮度:

The Brightness slider on the Color or Luminance page (whichever one the HDRI is loaded into) of the HDRI material. The brightness can also be set higher than 100% by setting the Mix parameter to Multiply and by manually typing in a Brightness value. (You can fine-tune the HDRI further still using Cinema 4D’s Filter shader.) You should use this method if you are using the HDRI as a visible background image because the first method only changes the amount of light cast by the image, not the brightness of the image itself. The first method also does not change the brightness for reflections. 在 HDRI 材质的“颜色”或“亮度”页上的“亮度”滑块(无论何种 HDRI 加载到其中)。亮度也可以通过设置 Mix 参数为 Multiply 和手动输入亮度值来设置高于100% 。(您可以进一步微调 HDRI 仍然使用Cinema 4D 的滤镜着色器。)如果您使用 HDRI 作为可见背景图像，则应该使用此方法，因为第一种方法只改变图像投射的光量，而不改变图像本身的亮度。第一种方法也不改变反射的亮度

The texture interpolation type also affects the brightness of the HDRI. MIP mapping, for example, softens the texture which enlarges the bright areas of a HDRI and results in brighter renderings. 纹理插值类型也会影响 HDRI 的亮度。例如，MIP 映射软化了纹理，扩大了 HDRI 的亮区，产生了更亮的渲染效果

When using GI, the extreme differences in brightness in a HDRI can lead to patches, especially on flat surfaces such as a floor. In such cases, use MIP mapping and increase the Blur Offset value for the HDRI texture to smooth out the areas of extreme brightness The objects will be much more evenly lit as a result. 当使用 GI 时，HDRI 中亮度的极端差异可能导致补丁，特别是在平坦的表面，如地板。在这种情况下，使用 MIP 映射，增加 HDRI 纹理的模糊偏移值，以平滑极端亮度的区域，结果物体将更加均匀地被照亮 Tip 2: 贴士二:
Note that you can define multiple Sky objects, which can be assigned separately to GI ( 注意，您可以定义多个 Sky 对象，它们可以分别分配给 GI (Visible for GI 可见的胃肠道), reflection ( )、反射(Visible for Rays 可见光) or background ( )或背景资料(Visible for Camera 可见的相机) using the )Compositing 合成 tag. 标签

For example, this lets you use a very blurred HDRI texture for lighting and the original HDRI texture for reflections.

例如，你可以使用一个非常模糊的 HDRI 纹理作为光源，使用原始的 HDRI 纹理作为反射。

However, when using this method, you will probably still want your reflections and background to be as crisp and sharp as possible. So it is a good idea to use two Sky objects — one for generating GI and the other just for the reflections and as a background. Both Sky objects must have a Compositing tag assigned. For the one which is used for GI, disable the options Seen By Camera and Seen By Rays. For the one which is used for the reflections and as a background picture, disable the Seen By GI option.

然而，当使用这种方法时，你可能仍然希望你的反射和背景尽可能的清晰和锐利。因此，使用两个天空对象(一个用于生成 GI，另一个只用于反射和作为背景)是一个好主意。两个天空对象都必须分配一个合成标记。对于一个是用于 GI，禁用选项看到由照相机和由射线看到。对于一个是用于反射和作为背景图片，禁用可见的 GI 选项。

Convert HDR Cross...
Convert HDR Probe...

转换 HDR 交叉... 转换 HDR 探针..。

Some HDRIs come as Probe or Cross projection types. To get the best result in Cinema 4D, these should be converted to Latitude/Longitude (spherical) maps and projected onto a SKY object. For this purpose there are two plugins included — Convert HDR Cross and Convert HDR Probe — which are available from the File menu. Choosing one of these commands opens a file selector. Select the HDR Probe or Cross image that you want to convert.

有些 hdri 是探针或交叉投影类型。为了在 Cinema 4D 中获得最佳效果，这些应该转换为纬度/经度(球面)地图，并投影到 SKY 对象上。为此目的，有两个插件包括: Convert HDR Cross 和 Convert HDR Probe，这两个插件可以从 File 菜单中获得。选择其中一个命令将打开一个文件选择器。选择要转换的 HDR 探针或 Cross 图像。

The image will be converted to a Latitude/Longitude map and saved in the same folder with the extension _con.HDR added to the file name. As soon as the HDRI has been converted you will see it appear in the Picture Viewer.

该图像将被转换为纬度/经度地图，并保存在同一个文件夹中，扩展名为 _ con.HDR 添加到文件名中。一旦 HDRI 被转换，你会在图片查看器中看到它。