Z-Buffer Algorithm

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• page=29

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A Hidden Surface Elimination algorithm which ignores transparency. It uses a color buffer, and a depth buffer. Each new primitive is checked against the current z buffer, and if it is closer (smaller), then the depth buffer is updated, and the color is also updated. The code below is the core of the algorithm.

Where

• $\mathbf{p}=(x_p,y_p)$ is the pixel of interest
• $(z_p,c_p)$ is the current stored value in that point (depth and color).

Runtime is either $O(pD)$ or $O(Ps)$, where

$$\begin{array}{rl}P& :\text{ \# of primitives}\\ s& :\text{ average \# of pixels covered by a primitive}\\ p& :\text{ \# of pixels}\\ D& :\text{ Depth complexity}\end{array}$$

Depth complexity is the average number of depth tests per pixel.