# Roof Design - Arc

The "arc" function allows a section of a roof-edge line to be pulled out of the roof surface in a circular manner. The midpoint of the partial line is shifted perpendicular to the partial line.

The arc can be shifted either outward or inward.

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A segment of an eaves is pulled out. A circular contour is created, bounded by the two selected points. The further the arc is pulled out, the smaller the radius becomes, until the radius is exactly half the distance between the two selected points. The center cross then lies precisely on the modified line of the averaging polygon. If the arc is pulled further, the radius increases again.

For this function, first select the line from which a portion is to be moved. Then select two points that define the area to be moved. You may use all usual snap and input functions for this. The points do not have to lie on the line; they can be chosen anywhere. Each selected point is then projected onto the chosen line. For the second point, using the arrow key is also convenient when the line appears exactly horizontal or vertical on the screen. You can then simply enter a distance from the first point.

If the intention is to deform the entire line in a circular manner, select the start and end points of the line.

Next, the midpoint of the selected line can be moved graphically and placed at the desired location. All snap and input functions are available for this. During the move, the point can only be shifted perpendicular to the selected line.

After placing the point, a dialog box opens where you can correct the point's position again. When any number is changed, the other numbers will adjust automatically if necessary.

**Batten spacing / covering width of standard tiles:** If tiles have been entered on the roof, the position of the point can be adjusted to the tile cover length or cover width. Depending on which line was deformed (e.g., eaves or verge), the text then changes. If the deformed line is not parallel to the fall direction of the roof surface (verge) and not perpendicular to the fall direction (eaves), then adjustment to the tiles is not possible. In that case, it is also no longer meaningful.

> This field automatically displays the cover length or cover width of the tiles used. However, the value can also be changed.

**Number of tile rows:** This field specifies the number of tile rows. Immediately after deforming the line this is usually a non-integer value, which is why the field is highlighted in red as an indication. Using the plus and minus buttons at the right end of the field, the value can be increased or decreased. The value is always adjusted to an integer and the red marking disappears.

**Shift within the roof surface:** This value shows the distance of the new point to the old line, measured in the slope of the surface.

**Displacement in base Y:** This shows the horizontal displacement from the old position of the line to the shifted point of the circular arc.

**Vertical displacement:** This value indicates the height difference between the old line and the shifted point of the circular arc.

**Elevation of the lowest point:** This field displays the absolute elevation of the shifted point, measured from global zero. If the arc is shifted inward, this is actually the highest point of the arc. Because this case is likely to be very rare, the text was chosen accordingly.

**Number of segments of the arc:** The arc is not actually created as a true circle but is segmented. This is necessary because the roof layer panels must also be adjusted as volumes. For this reason, the number of segments can be entered here. The value should not be chosen too large, as this would unnecessarily increase the data volume. For safety reasons, the program may correct the number so that a minimum line length of 0.05 m is achieved.
