# Understanding representation geometry logic

This topic applies to ArcEditor and ArcInfo only.

Since geometric effects alter geometry and even, in some cases, geometry type, it is important to ensure that representation rules maintain geometric logic. Geometric effects operate sequentially. The output of one geometric effect becomes the input of the following one, so you can use a chain of geometric effects to achieve the appropriate geometry logic. Regardless of how the geometry is dynamically changed through the chain of geometric effects, the final output of the last effect must match the geometry type of the symbol layer. If a warning symbol appears on the heading of the symbol layer, there is a disconnect in the geometry logic. The symbol layer you just added doesn't have any geometry to symbolize.

Valid and invalid geometry to symbol layer combinations

Polygon geometry

Line geometry

Point geometry

Fill symbol layer

Symbolizes polygon interior

Produces geometry logic error because there is no polygon geometry to fill

Produces geometry logic error because there is no polygon geometry to fill

Line symbol layer

Symbolizes polygon outline

Symbolizes lines

Produces geometry logic error because there is no line geometry to draw

Marker symbol layer

Places markers in polygons with a marker placement style

Places markers on lines with a marker placement style

Places markers on points with a marker placement style

Geometry-symbol layer combinations

For example, adding a fill layer to a line representation rule would generate a warning because there is no polygon geometry to fill. To repair the logic, add a line-to-polygon geometric effect to either the fill layer or the global effects portion of the rule. However, the opposite scenario—adding a line symbol layer to a polygon representation rule—would not generate a warning, because the line symbol layer will symbolize the outlines of the polygon geometry.

Changing geometry dynamically as you symbolize features with representations

To change input geometry

To output geometry

Use

Example

Point

Point

• A point input marker placement style

• On Point marker placement style

Point

Line

• A point-to-line geometric effect
• A point-to-polygon geometric effect

• Radial from Line geometric effect
• Buffer geometric effect

Point

Polygon

• A point-to-polygon geometric effect

• Buffer geometric effect

Line

Point

• A line input marker placement style

• Along Line marker placement style

Line

Line

• A line symbol layer alone
• A line-to-line geometric effect
• A line-to-polygon geometric effect

• Line symbol layer alone
• Simplify geometric effect
• Enclosing Polygon (Convex Hull) geometric effect

Line

Polygon

• A line-to-polygon geometric effect

• Enclosing Polygon (Rectangle Box) geometric effect

Polygon

Point

• A polygon input marker placement style

• Randomly Inside Polygon marker placement style

Polygon

Line

• A line symbol layer alone
• A line-to-line geometric effect
• A line-to-polygon geometric effect

• Line symbol layer alone
• Cut Curve geometric effect
• Donut geometric effect

Polygon

Polygon

• A fill symbol layer alone
• A polygon-to-polygon geometric effect

• Fill symbol layer alone (Hatch style)
• Offset Curve geometric effect (with negative value)

Changing geometry dynamically as you symbolize features with representations

5/2/2011