Alpha

阿尔法

An alpha channel enables you to use an image to mask out areas of the material, allowing any background to show through. This is useful for faking detail in 3D. The idea is to define areas of the material that effectively become non-existent so that any underlying materials or objects show through. A classic example would be a 3D tree. Rather than modeling the individual tree, a picture of a tree can be added to an object and an alpha used to cut out the shape of the tree.

阿尔法通道使您可以使用图像来掩盖材质的区域，允许任何背景显示通过。这对于在3D 中伪造细节很有用。这个想法就是定义那些实际上已经不存在的材质区域，这样任何基础材质或物体都可以通过这些区域显示出来。一个经典的例子就是3D 树。树的图片可以添加到一个对象中，而不是单独建模一棵树，阿尔法用来裁剪树的形状。

If you notice black areas when rendering objects that have multiple alpha materials, increase the Ray Depth value on the Options page of the render settings.

如果在渲染具有多个 alpha 材质的对象时注意到了黑色区域，请在渲染设置的选项页面上增加 Ray Depth 值。

If you apply a material with a Cinema 4D Alpha channel to an object and the object has no underlying material, the object will be non-existent at the points where the alpha allows the underlying material to show through.

如果你将一种具有 Cinema 4D Alpha 通道的材质应用到一个物体上，而该物体没有底层材质，那么在 Alpha 允许底层材质通过的地方，该物体将不存在。

Suppose you want to place a scanned picture of a tree into a scene. First, you should create a material, enable the Color channel, choose a picture of a tree as the color texture and then assign this material to, perhaps, a rectangular polygon.

假设你想把一张扫描的树的图片放到一个场景中。首先，你应该创建一个材质，启用颜色通道，选择一个树的图片作为颜色纹理，然后将这个材质分配给一个矩形多边形。

If you render this scene, you should see the tree on the rectangle polygon. However, the area around the tree is probably not transparent, but blue if the scanned picture has a blue sky background (Figure 1).

如果你渲染这个场景，你应该看到在矩形多边形上的树。然而，如果扫描的图片是蓝色的天空背景，那么树周围的区域可能不是透明的，而是蓝色的(图1)。

Now edit the tree material, enable the Alpha channel, switch to the Alpha page and load the Tree texture there. First, disable the Soft option. Ctrl+click on the area you want to mask — in our case, the blue sky around the tree (Figure 2).

现在编辑树材质，启用 Alpha 通道，切换到 Alpha 页面并加载树材质。首先，禁用 Soft 选项。按 Ctrl + 单击要蒙版的区域ー在我们的例子中，是树周围的蓝色天空(图2)。

Cinema 4D sets the color sliders to this color and masks according to the picture. The tree is now shown without the surrounding background (provided that you have Gouraud Shading or Quick Shading on). You can now select a slightly different color on the Alpha page and see the effect immediately. However, some background may be left around the leaves, branches and the trunk. So the result is not quite right yet.

C4D根据图片设置颜色滑块为这种颜色和蒙版。树现在显示没有周围的背景(如果你有 Gouraud 阴影或快速阴影)。您现在可以在 Alpha 页面上选择稍微不同的颜色，并立即看到效果。然而，一些背景可能会留下周围的叶子，分支和树干。因此，结果还不完全正确。

For a more accurate result, create an alpha channel in your image editor and integrate this into the tree image; for details on how to do this, consult you image editor’s help. Load this picture into the Alpha channel and enable Soft and Image Alpha. The texture is now masked cleanly (Figure 3).

要获得更准确的结果，请在图像编辑器中创建一个 alpha 通道，并将其集成到树形图中; 有关如何做到这一点的详细信息，请咨询图像编辑器的帮助。加载此图片到阿尔法通道，并启用软件和图像阿尔法。纹理现在被干净地掩盖了(图3)。

Two materials were used to create the intricate box below: A reflective gold material and a matt wood. To make the wood visible, one of the two colors was cut out from a scanned black-and-white picture.

两种材质被用来创建下面的复杂的盒子: 反射金材质和亚光木材。为了使木材可见，两种颜色之一被从扫描的黑白图片中剪下来。

Alpha Channel and Antialiasing Filter

阿尔法通道和反走样滤波器

Depending on the Filter Antialias settings, the Alpha channel can end up being smoothed as well. This can result in problems in subsequent compositing, especially when the Sinc filter, which can - as pictured above - "overshoot", i.e., generate an edge, is used. Antialiasing filters can, depending on their settings, extend their effect beyond the edge of an object. This can be minimized by either selecting a different filter or by using smaller Filter Width and Filter Height values.

根据过滤器的消除别名设置，阿尔法通道可以最终平滑以及。这可能会导致后续合成中的问题，特别是当使用 Sinc 过滤器时，如上图所示，它可以“超调” ，即生成边缘。反走样过滤器可以，根据他们的设置，扩大其效果超过边缘的对象。这可以通过选择不同的过滤器或使用更小的过滤器宽度和过滤器高度值来减少。

Color
Delta

Clipping is often attempted with texture images that are antialiased; this produces a bright border around an object caused by the antialiasing of colors between the main texture and the alpha color; you can remove this border by adjusting the deviation sliders.

剪切通常尝试使用反走样的纹理图像; 这会在对象周围产生一个明亮的边框，这是由主纹理和 alpha 颜色之间的反走样引起的; 你可以通过调整偏移滑块来移除这个边框。

You can use clip mapping (also sometimes called genlocking) to mask particular areas with a Color value. Using this method, you pick the color from the selected image that you wish to become transparent. The downside is that often the areas you wish to become transparent contain several colors and the resulting alpha can leave a seam around the object. However, by setting the Delta color, you can define by how much the color may deviate; this can help to reduce the seam.

您可以使用剪辑映射(有时也称为 genlocking)来用 Color 值掩盖特定区域。使用此方法，您可以从选定的图像中选择希望变为透明的颜色。缺点是，您希望变得透明的区域通常包含几种颜色，结果 alpha 会在对象周围留下一个缝隙。但是，通过设置 Delta 颜色，可以定义颜色偏离的程度; 这有助于减少接缝。

Use alpha channels built in to the texture to mask areas softly and more accurately (see Image Alpha below).

使用内置于纹理中的 Alpha 通道可以更加柔和和准确地遮盖区域(参见下面的图像 Alpha)。

Invert

This option simply inverts the alpha, so transparent and solid areas are reversed. This works for both clipped images and images with built-in alpha channels.

这个选项只是简单地颠倒 alpha 值，因此透明和实心区域是颠倒的。这对于剪辑过的图像和内置 alpha 通道的图像都适用。

Soft

柔软

This enables you to fade textures and materials from one to another, which gives you even more ways of creating realistic-looking objects. With Soft enabled (the default setting), the Color and Delta settings lose their meaning. The texture map is now used to decide which ranges should be faded. A white texture pixel in the image means that here the material is to be 100% opaque. If the texture pixel is black, the underlying material shines through 100%.

这使您可以将纹理和材质从一个淡化到另一个，从而给您提供更多创建逼真对象的方法。使用软启用(默认设置) ，颜色和三角洲设置失去了它们的意义。现在使用纹理贴图来决定哪些范围应该褪色。图像中的白色纹理像素意味着这里的材质是100% 不透明的。如果纹理像素是黑色的，那么底层的材质将100% 闪耀。

Image Alpha

图片 Alpha

With Image Alpha enabled, you can use any existing alpha channel of the loaded image. A list of supported formats can be found here. If no alpha channel is present in the image, the Image Alpha option will be ignored. Use the Invert function to invert the alpha channel without having to rework the texture in your image editor.

启用 Image Alpha 后，您可以使用加载图像的任何现有 Alpha 通道。支持的格式列表可以在这里找到。如果图像中没有 Alpha 通道，则图像 Alpha 选项将被忽略。使用反转函数来反转 alpha 通道，而无需在图像编辑器中重新制作纹理。

Pre-multiplied

预繁殖

Enable this option if you are using a texture with a premultiplied alpha channel. Certain graphics applications only produce this type of alpha channel.

如果使用的纹理是自前乘的 alpha 通道，请启用此选项。某些图形应用程序只产生这种类型的 alpha 通道。

Texture

纹理

Here an image texture or a 2D shader can be defined. Refer to the Textures chapter for details.

这里可以定义一个图像纹理或二维着色器。详细信息请参阅纹理章节。