View source for How to compute residential walls with sight of trees

For the [[Demo 3-30-300 Project|3-30-300]] guidelines, the rule indicated by the "3" is the ability to see 3 trees out of residential windows. This can be computed in the {{software}} by calculating the locations of residential walls, and the sight-lines onto trees.

{{editor location|Overlays}}

{{editor steps|title=compute residential walls with sight of trees
| [[How to add an Attribute to a Function|Add an Attribute to the Function]] of Default Deciduous Trees, naming the attribute TREE_SIGHT_DISTANCE.
| [[How to change Attributes for a Function|Configure the value]] of the TREE_SIGHT_DISTANCE of Default Deciduous Trees as "100".
| Add a [[Sight Distance Overlay]], configured so that:<br>The [[Attribute]] it references is TREE_SIGHT_DISTANCE.
| [[How to make a Grid Overlay of residence walls|Create a Grid Overlay of residence walls]].
| Add a [[Combo Overlay]], configured so that:<br>Input A: The [[Grid Overlay]] of residence walls.<br>Input B:The [[Sight Distance Overlay]] for the sight onto trees.<br>Formula: <code>IF(EQ(A, 0), NO_DATA, GT(B, 0))</code>
| Configure the legend of the [[Combo Overlay]] to have a distinct entry for the value "0" and the value "1".
}}

{{article end
| notes=
* The resulting [[Combo Overlay]] has values of 0 where there are walls without sight of a tree, and values of 1 where there are walls with sight of a tree.
* Although the different steps in the calculation may produce coarse results, over a large scale the imperfections can balance out and the calculation as a whole can provide relevant insights into the compliance to the guideline.
* At this time this calculation can only determine sight-lines to ''a'' tree, not necessarily to the prescribed 3 or more trees. However, in most urban environments trees exist in groups which can alleviate the discrepancy somewhat.
|seealso=
* [[Demo 3-30-300 Project]]
}}

[[Category:How-to's]]