# 运算节点¶

## 范例¶

### 自定义Z深度通道节点设置¶

This example has one scene input by the top Render Layer node, which has a cube that is about 10 BU from the camera. The bottom Render Layer node inputs a scene (FlyCam) with a plane that covers the left half of the view and is 7 BU from the camera. Both are fed through their respective Map Value nodes to divide the Z-buffer by 20 (multiply by 0.05, as shown in the Size field) and clamped to be a min/max of 0.0/1.0 respectively.

“使用最小值”功能是依据靠近摄影机的像素将Z深度值选择出来；也可以选择矩形部分的平面Z深度值。背景有个初始的Z深度值，值限定为1.0（显示为白色）。在“使用最大值”范例中，矩形的Z深度值比图像平面要大，因此更靠近左侧，但是图像平面(FlyCam)渲染层Z值初始在右侧（对应于1.0），因此他们被选择。

## 理论¶

Note

### 总结¶

JPGPNG 图像格式依据颜色位深(比如： JPG 是 24位颜色位深)存储每个颜色值，但是生成图像体积非常小的原因是依据 JPEG 压缩算法减少颜色位深和量化颜色范围。