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DDScad Help Lines and Coordinate Geometry

Introduction to Help Lines

In the drawing, we can add help lines. We use these to calculate:

  • Intersection points
  • Tangent points
  • Normals
  • Roundings
  • Circles/arcs
  • Parallel lines

We can use elements in the drawing, the map, and other help lines to construct new help lines.

Where help lines intersect, the program can snap to a point. Using these lines, we can construct the points we need.

Modes for Help Lines

Help lines have two different modes:

  1. Line mode
  2. Point mode

Line Mode

We activate line mode by holding down the [Ctrl] key. When help geometry is activated and there is a cursor on the screen, you will see that when the cursor is moved over lines, they will be highlighted in orange so that we can control which line is active. You can then press the right mouse button and a menu will appear with several available functions for drawing help lines.

Point Mode

Point mode is active when the cursor is moved over a point and it is marked with a snap point (the snap icon must be active). In addition, we can freely activate point mode by holding down the [Shift] key. When point mode is active, you can press the right mouse button and a menu will appear with several available functions for drawing help lines.

Note

[Ctrl] and [Shift] are always available even if we are in a sequence, for example editing points in a line.

Practical Examples

We recommend that you try it yourself. Help lines are temporary lines that can easily be removed from the screen, and that do not cause any "damage".

Example 1: Extension of a House Wall

Calculate the coordinates of a point located 5 m in the extension of a house wall.

Help line example 1

Extension of house wall with help line and help circle

Instructions

  1. Place a help line along the house wall:
    • Hold down the [Ctrl] key
    • Point at the house wall
    • Right-click (when the house wall line is active)
    • Select Stretch as help line
  2. Place a help line circle at the house corner:
    • Hold down the [Shift] key
    • Point at the house corner
    • Right-click (when the snap point is active)
    • Select the icon Help circle from point
    • Enter radius 5 m
  3. Now the intersection point between the line and circle is active for snapping. You can, for example, create a point object in the application layer at the intersection point.

Example 2: Rounding Between Lines

Round between lines, for example for construction of road center line.

Help line example 2

Rounding between lines with help circle

Instructions

  1. Add help lines:
    • Hold the [Ctrl] key and right-click
    • Select the icon Construct circle tangent to other
    • Enter radius, point at the 1st line and left-click, point at the 2nd line and left-click
    • The program now dynamically shows possible solutions. Left-click when the desired circle is displayed
  2. Now the intersection point between line and circle is active for snapping. You can, for example, construct a line in the application layer that follows the arc.