Kubla Cubed User Manual
Reduce, Raise, Trench and Berm, are all Relative element types.
In Kubla Cubed, relative elements are those that are specified with heights or depths. For instance, a trench defined as 2ft below the ground surface is characterised by a relative depth. The alternative form, ‘absolute elevations’ would have elevations defined from a fixed datum (e.g., 156m from Sea Level). Typically, existing terrain is defined with absolute elevations whereas proposed terrain can be defined with a combination or relative and absolute elevations. For example, a topsoil strip is almost always defined with relative elevations (e.g. 1 ft topsoil strip), whereas building pads are defined with absolute elevations (e.g. 245ft FFL).
Each element that is defined by depths has an inverted counterpart defined by heights. The Trench has depth values, while the Berm has height values, both are defined by a centreline. Similarly, the Reduce element's opposite number is the Raise element. You can specify heights in a depth element and/or depths in a height element, by using negative values.
Relative elements all have a property called ‘Depths From’ or ‘Heights From’. This property allows you to specify the surface to which the elevations are relative. An obvious choice is to make them relative to the ground surface, meaning they will override each other in areas of intersection, with the element lower in the calculation order taking precedence. However, having the elevations relative to ground is not always desirable. For instance, if you wanted to reduce a slab level for a material thickness in a specific area, you would want the depths defined from the slab level, not the ground. The ability to change what the depths/heights are relative to is extremely powerful, allowing you to adjust the surface of lower elements in the calculation order, as well as the ground. In 'Depths/Heights From', you can select 'Ground', the 'Previous Element' or a named element.
When the ‘Auto’ option is active, the option is dynamically set to the first absolute element above it in the calculation order. If there aren’t any, it is set to ground. It can be conceptually confusing to have relative elements adjust each other, especially for new users to the program, so the auto option ensures the relative elements adjust only from previous absolute elements in the calculation order or ground if no absolute elements are found. The option is dynamic so you can add and remove elements, and all the relative adjustments elements will update accordingly.