How to Create Alignments in BricsCAD

Quick answer: An alignment is a reference system for positioning linear objects like roads, railways, or pipe networks in space, made of a horizontal 2D curve, an optional vertical 2D curve, and the 3D curve those two combine to form. Create one by points of intersection, by individual elements, or by importing from LandXML or Civil 3D.

About Alignments

• Horizontal alignment: a 2D curve positioning a linear object horizontally. It’s the horizontal trace on a TIN surface used to generate an elevation profile and vertical alignment, though it isn’t always projected (draped) onto the surface, projection is required before you can create a vertical alignment or a corridor from it. Each horizontal alignment can have only one vertical alignment, and displays underneath the surface visually.
• Vertical alignment: positions a linear object vertically, defined by Points of Vertical Intersection (PVI) on the vertical profile of the target surface.
• 3D alignment: a 3D polygonal curve defined by combining the horizontal and vertical alignments.

Creating an Alignment by Points of Intersection

1. Open a drawing containing a TIN surface.
2. Launch ALIGNMENT.
3. Select the TIN surface.
4. Optionally choose Specify start station to set where the alignment begins.
5. Pick the horizontal alignment’s PI points on the surface, then press Enter.

This generates three visible alignments: the horizontal alignment itself (on the 0,0 plane), a light blue 3D alignment showing the horizontal alignment’s projection onto the TIN surface, and a purple 3D alignment representing the automatically generated design alignment.

Creating a Horizontal Alignment Without 3D Alignments

1. Open a drawing and launch ALIGNMENT.
2. Choose the Pick pi point option (this skips projecting the alignment onto the TIN surface).
3. Optionally choose Specify start station.
4. Pick the horizontal alignment’s PI points, then press Enter.

Creating a Vertical Alignment View

The horizontal alignment creates a vertical section of the target TIN surface, and ALIGNMENTVIEW displays this 2D curve in a separate viewport within model space.

1. Open a drawing containing a TIN surface, horizontal alignment, and 3D alignments.
2. Launch ALIGNMENTVIEW.
3. Select a horizontal or 3D alignment. If the horizontal alignment isn’t yet projected onto the TIN surface, you’ll also need to select the TIN surface next.
4. Pick a point as the origin for the vertical alignment view.

Two lines appear: a light blue terrain line from the TIN surface, and the vertical alignment itself, made of straight lines and vertical curves generated automatically based on the Vertical Tolerance parameter’s accuracy factor, adjustable in the Properties panel.

Creating a Vertical Alignment

1. Open a drawing containing a TIN surface, horizontal alignment, and vertical alignment view.
2. Launch ALIGNMENTVERTICAL.
3. Select the vertical alignment view.
4. Pick the vertical alignment’s PVI points, pressing Enter when done (use Undo to step back if needed). The Automatic 3d alignment option generates the vertical alignment for you.

Attaching an Element Before or After an Existing One

1. Draw a horizontal alignment using ALIGNMENTLINE or ALIGNMENTCURVE.
2. Launch ALIGNMENTELEMENTFROM. You’re prompted to choose an element type: Line, Curve, Spiral, Line with Spiral, Curve with Spiral, or Curve-Spiral-Spiral.
3. Choose the type you want, Curve with Spiral, for example.
4. You’re prompted to choose Element (attach to a specified point on the attachment element) or element END (attach to its start or end point specifically). Click closer to the attachment element’s start point to attach the new element before it, or closer to its end point to attach after it.
5. Select the existing element to attach to.
6. Specify the spiral radius.
7. Specify the spiral length.
8. Specify the curve solution angle (greater or less than 180 degrees).
9. Specify the curve’s pass-through point to draw the combination.

The new element always draws tangential to the specified point on the selected attachment element.

Attaching an Element Between Two Existing Ones

1. Draw a horizontal alignment with two elements, using ALIGNMENTLINE or ALIGNMENTCURVE.
2. Launch ALIGNMENTELEMENTBETWEEN. You’re prompted to choose an element type: Line, Curve, Spiral, Spiral-Curve-Spiral, Spiral-Spiral, or Spiral-Line-Spiral.
3. Choose the type you want, Spiral-Curve-Spiral, for example.
4. Select the first attachment element.
5. Select the second attachment element.
6. Specify the curve radius.
7. Specify the spiral in length.
8. Specify the spiral out length.

The new combination is added between the two selected elements, drawn tangential to both.

Frequently Asked Questions

Does a horizontal alignment always project onto the TIN surface automatically? No, and it needs to be projected before you can create a vertical alignment or corridor from it. Choosing the Pick pi point option specifically skips this projection.

Can one horizontal alignment have more than one vertical alignment? No, each horizontal alignment can have only one.

What’s the difference between attaching an element “before or after” versus “between” two existing elements? ALIGNMENTELEMENTFROM attaches a new element to one existing element, before or after it depending on where you click. ALIGNMENTELEMENTBETWEEN connects two separate existing elements with a new one bridging them, tangential to both.

Do the element type options differ between attaching before/after versus between? Yes, ALIGNMENTELEMENTFROM offers Line, Curve, Spiral, Line with Spiral, Curve with Spiral, and Curve-Spiral-Spiral, while ALIGNMENTELEMENTBETWEEN offers Line, Curve, Spiral, Spiral-Curve-Spiral, Spiral-Spiral, and Spiral-Line-Spiral.