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Precedence of Lines

When obtaining orthographic views, it is common for one type of line to overlap another type. For example, perhaps a continuous line belongs in the same location as a hidden line. When this occurs, drawing conventions have established an order of precedence. A continuous line takes precedence over a hidden line and a hidden line takes precedence over a centerline.

Examples of Lines

So, for our example of a hidden line and a continuous line at the same location, the continuous line would have precedence and would therefore be shown. The hidden line would be omitted.

If the line types are of different lengths it is important to distinguish one line type from another. Including a gap between the end of one line type and the start of the other does this.

Precendence Grid

For this object, when the square cut out is projected to the top view, it will be hidden and it will be located in the exact same location as the continuous line that locates the change from the horizontal surface to the slanted surface. Based on the order of precedence of lines, the hidden line is omitted from the top view.

Slanted Surfaces >>