Vertical Variation Fixed Level
Apply one constant target elevation to all corridor stations — ideal for flat bridge decks or when a single design elevation controls the full span. No Civil 3D, no linked files required.
Fixed Level Method
The Fixed Level method applies a single constant target elevation to every corridor station. For each nested adaptive instance, AutoBRIDGE computes the absolute difference between the instance's current world Z and the fixed elevation — writing that delta to the selected family parameter.
Because the corridor base Z may undulate slightly along the bridge, the parameter values will vary slightly station by station — but the result is that the top of each instance aligns to the same horizontal elevation throughout the corridor.
Full Form Layout
Five zones. Row A is the full-width Instances Family groupBox. Row B splits: Fixed Level in Meter (65%, with the elevation textBox1) and Parameter Direction (35%). The RUN button in Row E stands alone — no Alignment info label.
Select the Corridor Family & Parameter
Instances Family — comboBox5
Lists all AutoBRIDGE_Corridor families in the project. Selecting auto-populates comboBox4 with all length instance parameters found in the family.
Parameter Name — comboBox4
Pre-loaded with Top_variable and Bottom_variable. Must be an Instance length parameter with no formula.
Parameter Direction — Up / Down
Choose Up if the parameter grows upward from the instance base Z. Choose Down if it grows downward. Preview updates immediately on toggle.
Enter the Fixed Elevation & Run
Type the Target Elevation in Metres — textBox1
Enter the target elevation in the Fixed Level in Meter groupBox. The preview canvas updates in real time — a perfectly horizontal blue line appears at the entered level.
The delta written to each instance is |fixed elevation − instance base Z|. Base Z may vary slightly, so parameter values will differ slightly station by station — but all tops align to the same elevation.
RUN Pipeline
Read nested instances from corridor family
Opens the family for editing and retrieves all nested adaptive instances.
Read current base Z of each instance
Gets world Z of each instance LocationPoint.
Use fixed elevation as target for all stations
The value in textBox1 is applied uniformly — no external query needed.
Compute |fixed elevation − base Z| per instance
Each instance gets its own delta. Absolute difference always positive.
Write delta to the selected parameter
Single transaction: sets the parameter on every nested instance.
Delete old forms and rebuild solid/void geometry
CreateLoftForm called for each solid then void subcategory.
Reload family into the Revit project
Updated geometry immediately visible. Preview redraws.