Step 3 · Point List Management

Analyse the adaptive component's points, then manipulate lists to build the point sets you need.

Overview

Create sub-lists of points from the elevated points generated by Curve.PointAtParameter in Step 2, arranged into the data structure required to host the Revit adaptive components. Understanding lists and data structures is a fundamental computational-design skill. By the end of this step you will have:

Analysed and understood the problem.
Generated the point sets required for adaptive-component placement.

Objective 3.1: Analyse the problem

Before building anything, understand how the adaptive component is constructed. Each adaptive component is defined by four adaptive points, and the order of those points must match the order of the points in the sub-lists you create:

The adaptive component family in Revit, defined by four numbered adaptive points.

Point 1 — top-left — call this pointA
Point 2 — top-right — call this pointB
Point 3 — bottom-right — call this pointC
Point 4 — bottom-left — call this pointD

In plan, the points map to pointA (top-left) through pointD (bottom-left).

In Dynamo, the points you have are not yet structured into sub-lists of four. Reshaping data to meet an objective is a common task in procedural modelling, and the rest of this step shows how.

Start by mapping the indexes in the existing data structure (the same [row][column] structure as the point-grid diagram in Step 1.3). For any group of four neighbouring points: pointA is at [0][0], pointB at [0][1], pointC at [1][1], and pointD at [1][0].

One adaptive component spans four neighbouring points — [0][0], [0][1], [1][1], [1][0].

If this observation is mapped across the entire point grid, it's possible to segregate the point grid into absolutes. For example, all the pointA are located within the blue zone shown in the diagram below. None can be found at the right or bottom of the point grid, as there are no neighbouring B, C or D points.

The pointA zone — never the right column or bottom row.

The pointB are located within the blue zone shown in the diagram below. None can be found at the left or bottom of the point grid, as there are no neighbouring A, C or D points. Also note that the bottom row of points is never used by either pointA or pointB — an observation we can apply in Dynamo when creating the required data structure.

The pointB zone — never the left column or bottom row.

The pointC are located within the blue zone shown in the diagram below. None can be found at the left or top of the point grid, as there are no neighbouring A, B or D points.

The pointC zone — never the left column or top row.

The pointD are located within the blue zone shown in the diagram below. None can be found at the right or top of the point grid, as there are no neighbouring A, B or C points. Also note that the top row of points is never used by either pointC or pointD — an observation we can apply in Dynamo when creating the required data structure.

The pointD zone — never the right column or top row.

Objective 3.2: Generate the point sets

Now apply the analysis in Dynamo. Start with the pointA and pointB sets, using the elevated point grid from Curve.PointAtParameter (Step 2.3). Because neither set ever needs the last row (the last sub-list), remove it first.

To remove an item from a list, use the List.DropItems node — on a list of lists, each "item" is a sub-list, so the whole sub-list is removed. Connect the point grid into the list input, and set amount to -1 (negative values drop from the end of the list) using a code block or a Number node.

Dropping the last row, which neither pointA nor pointB uses.

Group this node with a meaningful name referencing the sets it defines.

pointA

To create the pointA set, drop the last point from each sub-list. Dynamo's @List level feature lets a node operate at a chosen list rank (depth). Place a new List.DropItems node and connect the previous node's output into its list input, with amount -1 again.

Enable @List level by clicking the > icon on the list input port and checking Use Levels. By default @L2 is selected, which means the node operates at the sub-list level (rank 2) — dropping the last point of each row rather than the last row.

@L2 makes the node operate on each sub-list.

pointB

To create the pointB set, copy the previous List.DropItems node. Because the first point of each sub-list must be removed, change its amount to 1.

Group these nodes and name them after the point set they output.

The pointA and pointB sets, each in its own group named after its output.

pointC and pointD

Creating the pointC and pointD sets follows a similar approach, but starts by dropping the first sub-list (the top row). Copy the node that dropped the last row and change its amount to 1.

Dropping the first row — the top sub-list that neither pointC nor pointD uses.

To create the pointC set, add a new List.DropItems node and connect that output into its list input. This set needs the first point removed from each sub-list, so set amount to 1 and @List level to @L2.

Create pointD by copying the previous node and changing its amount to -1, removing the last point of each sub-list. Group these nodes when complete.

The four point sets — pointA, pointB, pointC, pointD — ready to be recombined in Step 4.