How to Work with Gradings in BricsCAD

Quick answer: GRADING creates a graded surface on an existing TIN surface, maintaining a base level for construction work like parking areas, recreation reserves, or roads by defining a slope or offset. GRADINGEDIT merges, splits, or recalculates transitions between gradings, and GRADINGBALANCE adjusts elevation to balance cut and fill volumes.

The Two Projection Methods

• Slope to surface: needs an input entity (a polyline, line, arc, or circle, for example), a target surface, and a slope.
• Offset to slope: needs an input entity, an offset, and a slope.

Grading a Surface to Create a Pond

1. Open a drawing containing a topographical surface.
2. Launch GRADING.
3. Select the input entity defining the pond’s footprint; lines, polylines, 2D/3D polylines, arcs, 3D alignments, and even other gradings are all accepted. You can switch to the slope/offset method before selecting the target surface if needed.
4. Select the target surface.
5. Select part of the entity (a start and end point) or its entire length.
6. Define the slope. The grading attaches to the input entity and connects to the target TIN surface; moving the mouse in or out dynamically adjusts the slope. If DYNMODE is set to 3, you can type the slope angle directly from the keyboard instead.
7. Press Enter to accept.

Properties of a Graded Surface

Select a grading to see its properties in the Properties panel:

• Grading type: which projection method is in use, Slope to surface or Slope and offset.
• Input entity: the handle number of the input entity; change it via the browse (…) button.
• Target surface: the target surface’s name; also changeable via a browse button.
• Grading transition: the transition status.
• Cut slope: the cut slope’s start and end values.
• Fill Slope: the fill slope’s start and end values. (Octave’s own documentation describes this field with wording copied from Cut slope, “Displays the cut slope,” which looks like a copy-paste artifact rather than an intentional statement, this is what the field is actually for.)
• Region start / Region end: the region’s boundaries.
• TIN Visibility, TIN Analysis, TIN Statistics: inherited from the underlying TIN surface, since a grading is derived from it. You can also calculate a TIN Volume Surface and extract the TIN surface from here.
• Side: which side of the input entity the grading is drawn on, left or right.
• Infill: fills the internal area, valid for closed entities only (circles, closed polylines).
• Boundary: controls the grading’s boundary. When on, it’s added as a hide boundary to the target surface, which affects the net volume calculation.
• Fill volume, Cut volume, Net volume: the calculated volumes for the resulting body, bounded by the target and graded surfaces.

Grading a Surface to Create a Platform

1. Open a drawing containing a topographical surface.
2. Launch GRADING.
3. Select the entity defining the platform’s footprint. You can switch to the slope/offset method before selecting the target surface if needed.
4. Select the target surface.
5. Select the entire length of the input entity.
6. Define the slope, the same dynamic mouse adjustment or direct keyboard entry (with DYNMODE set to 3) as with a pond.
7. Press Enter to accept.

Afterward, you can move the platform using the Manipulator on the entity it was created from, both horizontally and vertically, and the grading adapts automatically to its surroundings as you move it.

Editing a Grading

GRADINGEDIT can:

• Merge two gradings into a single grading with several regions.
• Automatically calculate the transitions between gradings.
• Split a grading into multiple regions, each with its own independently editable slope.

To merge: merge the two gradings, connect their grips to close the result, then optionally build a further grading sloped to the TIN surface from that result, with its Infill parameter turned off.

To split: split the grading, then edit each resulting region independently by moving its grips.

Balancing Cut and Fill Volumes

GRADINGBALANCE raises or lowers the elevation of a grading’s input entity until its net volume sits around zero, within a tolerance you set.

1. Open a drawing containing a TIN surface and a grading, a building pad, for example.
2. Launch GRADINGBALANCE.
3. Select the grading.
4. Enter a tolerance as a percentage, from 1 to 100. At 1, the cut and fill volume difference will be under 1%; at 100, under 100%.

The Properties panel then shows the cut and fill volumes balanced accordingly.

Frequently Asked Questions

What entity types can define a grading’s footprint? Lines, polylines, 2D/3D polylines, arcs, 3D alignments, and even other gradings.

Can I move a graded platform after creating it? Yes, using the Manipulator on the entity it was built from. The grading automatically adapts to its surroundings as you move it.

What does the tolerance percentage in GRADINGBALANCE actually mean? It sets how close the cut and fill volumes need to end up. A tolerance of 1 means the difference stays under 1%; a tolerance of 100 allows up to 100% difference.

How do I edit the slope of just part of a grading, not the whole thing? Split the grading with GRADINGEDIT first, then adjust each resulting region’s slope independently by moving its grips.