Image bm807.GIF Depth Test
When rendering (drawing) objects each point being rendered is stored together with its depth information, i.e. with its distance from the camera. When rendering a further object each point being rendered is depth tested. A new point will be drawn only if it is situated nearer to the camera than the foregoing point.
The depth test element is a numeric parameter of an active object defining the precondition for rendering a point. The depth (distance) of the point is compared with the depth of the point being overwritten. The point will be drawn only if the test precondition is met.
1 never (pixel will never be drawn)
2 < (distance must be less)
3 = (distance must be equal)
4 <= (distance must be less or equal; default)
5 > (distance must be greater)
6 <> (distance must not be equal)
7 >= (distance must be greater or equal)
8 always (pixel will always be drawn)
The default value is 4; the point will be drawn if its distance from the camera is smaller or identical. After setting the depth test to 8 and switching the write depth information switch off the function of the depth buffer will be switched off. The rendering speed can be thus raised slightly, especially when using a software driver.

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