Go to the top Viewport and zoom/place the viewpoint so that the PDA fills most of the width of the Viewport.

Leave about a third of the PDA's width on both sides free (figure 41).

40. 设置错误动画行为

导出模型，给PDA建立新阴影。你需要建立一个合适的纹理，隐藏或删除PDA下的所有对象。进入top Viewport，拉伸镜头，给视口定位，这样能给PDA填充宽度。在两边空白处预留出1/3 PDA的宽度。

Figure 41: Position the View Like This

Render a still image, 128 pixels wide and 256 pixels high (note the 2n Dimensions).

We are only interested in the alpha channel of the resulting image. Click the alpha channel button to review the results (figure 42).

41. 视觉定位

先给出一个宽为128象素，高为256象素的静止图像（2维），我们仅需要结果图像的alpha channel，点击alpha channel键查看结果。（步骤42）

Figure 42: Alpha Channel of the Rendering

Save the image as a PNG file with RGB 24 bit and Alpha channel. Name the file 'ShadowMap.png'.Open the picture in Photoshop.Select the RGB channels in the channels window.Change the background color to black.Choose the marquee tool (keyboard shortcut [M]) and select the entire image (keyboard shortcut [Ctrl] + [A]).Press the delete key. See figure 43.

42. 给出alpha channel

用Alpha channel，以PNG 文件格式保存图像，命名文件为'ShadowMap.png'。在Photoshop中打开图片，在channels窗口选择RGB channels。把背景改为黑色，选择marquee工具（快捷键[M]），选定整个图像（快捷键[Ctrl] + [A]），按delete，见步骤43。

Figure 43: Delete All Contents of the RGB Channels Using a Black Background Color Now the entire image should be completely black.

The alpha channel should remain unchanged.Select the Alpha channel from the channels window. It will appear as a white silhouette on a black background.A black pixel means completely transparent and a white pixel means completely opaque. Anything in between is partially transparent. We want to make the shadow a little diffuse.Deselect all Menu: Select > Deselect Use Menu: Filter > Blur > Gaussian Blur … to soften up the edges of the shadow. Use a Radius around 8 (figure 44).

43. 删除所有RGB Channels内黑色背景的内容

现在整个图像都显示为黑色，alpha channel保持不变。在channel窗口中选择Alpha channel，使黑色背景上出现白色影阴轮廓。此时black pixel指的是全透明，white pixel指全非透明，而中间内容则为部分透明。我们需要把阴影部分向外散播，删除lMenu: Select > Deselect，选用Filter > Blur > Gaussian Blur，这样能柔化阴影的边缘，Radius选用8。（步骤44）

Figure 44: Blurred Alpha Channel

Save the picture.

Go back to max and create a plane in the top view, 220 long and 110 wide. Move it so that it is clearly below the PDA, 10 units down the Z-axis should do it.Enter the Material editor and make a new material in an empty slot. Make the diffuse color of the material completely black.

Assign the 'ShadowMap.png' file to the Opacity channel, open the Bitmap Parameters of the map and set the 'Mono Channel Output' to Alpha. This is not really used by TurnTool, but it ensures that max renders itcorrectly (figure 45).

44. 模糊Alpha Channel

保存图片。回到最大化，在top view创建一个220长110宽的新平面，把它移动至PDA下，Z轴下方10个单位。进入Material editor，在空槽内使用新材料，把材料的散播色完全变黑。在Opacity channel指定'ShadowMap.png'文件，打开Bitmap Parameters，为Alpha