# Web app

## Object function

Object function is an abstract representation for objects that have the same purpose. It allows users to define what is going to be calculated for each object falling under this category.
Examples of object category can be:
- Residential building
- Greenery area
- At-ground parking area
- Garage building


### Type
One of the defining aspect of object function is its type. It can be either area or a building. This will later on tell Rhino what objects are relevant. So even if at-ground parking ang garage parking share many similar aspects, it should be defined as 2 categories of different type. 

### Default floor height
For object function of building type, it is possible to define default floor height. It is a value the will be prefilled when creating specific category out given object function.

### Calculations
It is possible to define as many calculations for each object function as necessary. Each of these calculations represent something that will later on in Rhino going to be computed for each object. 
For Residential building object function the possible calculations might be:
- Number of apartments
- Number of tenants
- Parking spots needed
- and many more

Calculations are defined as a mathematical expression that will be evaluated in Rhino.

#### Calculation identifier
Each calculation must have an identifier. This identifier can be used when defining a metric.

### Variables
Variables have two important purposes. Firstly, they are building blocks needed to put together working formula. To give an example, number of apartments in building can be calculated as floor_area / average_apartment_size. Each object function have one variable available by default. It is area for areas and floor_area for buildings. This variable is calculated by the plug-in according to actual size of the rhino object. On top of that, it is possible to define as many variables as necessary to support various calculations for given object function.
That brings us to the second purpose of variables which is ability to create generic solution that will fit any use-case.
In reality, it means that users can derive multiple categories from each object function based on the actual values of variables.
To reuse the example with number of apartments, the average_apartment_size will be very different in english sub-urban areas and city center of Hongkong. To support both scenarios (and many more), it is only necessary to define the calculation using variable rather that fixed value and then creating multiple categories where the value assigned to given variable will reflect reality.

#### Default variable value

It is possible to provide default value that can be prefilled when creating project category out of an object function. 

#### Variable identifier
Each variable must have an identifier. This identifier can later be used to define a calculations. When evaluating the calculation, each identifier will be replaced by the actual value.

### Identifier
Each object function must have an identifier. Together with calculation identifier, it can be used when defining metric to identify results needed to compute given metric.


## Metrics
Metric provide a  way how to keep important metric of the project under control. Metric can be:
- Floor area ratio (FAR)
- Building Coverage Ratio (BCR)
- Parking spots demand
- and many more

Each metric is calculated for each sector in Rhino scene and also for the whole project.

### Expression
Metric is defined in similar way as calculation by mathematical expression. It is again composed from various variables but in this case, variables available for evaluating of the expression come from different source. They represent aggregated results for each calculation of every defined object function. To use such variable, it's necessary to tell the plug-in identifier of object function and identifier of this function's calculation separated by a dot. It can look like this.
OBJECT_FUNCTION_IDENTIFIER.calculation_identifier

Similar like in case evaluating object functions' calculations, the plug-in also provides couple of variables that is possible to use. It is:
SECTOR.area - area of given sector
BUILDINGS.area - aggregated footprint area of each building
BUILDINGS.floor_area - aggregated floor area of each building

To give couple of examples, Floor area ratio (FAR) can be calculated as total floor area / sector are. In this example, it is possible to get the result for FAR only by depending on variables provided by the plug-in so the expression can be defined as
BUILDINGS.floor_area / SECTOR.area

### Goal type
To have visual control over defined metrics, users can define the goal for each metric. If goal is not met, there will be an error displayed for given sector in Metrics tab. 
When defining a metric, users can choose out of three options. There can be:
- Constant goal - This option is important for metric like FAR or BCR, where a single value will determine whether the goal is met or not. If this option is selected, it is also possible to enter default value for the goal. It can be later overridden directly in the plug-in. Either for the whole section or for each of the sectors specifically to uphold local regulatory framework.
- Calculated goal - Calculated goal can come in handy for calculating parking spots demand where both sides of the equation are calculated. If this section is selected, it is necessary to also input expression for given metric's goal.
- None

### Goal criteria
This option will tell the plug-in whether the value of the metric is supposed to be higher or lower than its goal. This option is only available if calculated or constant goal is selected.

## Projects
Project is a set of information that the plug-in needs to start working and calculating all the defined outputs. Each project consists of saved set of categories that are relevant for areas with same or similar object functions' variable values.

Each category from the project can be assigned to a layer in Rhino project. That is the effective link that helps plug-in to determine purpose of objects located on the same layer and calculations that need to be evaluated for them.
There are two types of categories:

Category represents specific setting of selected object function that can be later assigned to a layer in Rhino document. That is the effective link that helps plug-in to determine purpose of objects on the same layer and calculations that need to be evaluated for them. There are two types of categories

### Simple categories
Simple category is a specific instance of an object function. To create one, it is necessary to select one and then provide values for each of its variables. If the variable has default value defined, it will be prefilled.
For building categories it is also needed to provide floor height (that can also be prefilled if object function provided default floor height)

### Mixed-use buildings
Chameleon.tools plug-in supports mixed-use building. These categories are composed from simple categories of the same project.
The building composition is defined from 'sections' with the same purpose. Each section tells the plug-in how many floors there is in the blog, what is its category (so also what things to calculate) and it is also possible to overwrite floor height of selected category. 
Building composition is defined from bottom to the top to resemble actual building and has exactly one special 'filling' section. Good example could be a building representing residential building located in a city center. There can be two floors of underground, ground floor for services and rest of the building offices. Composition for this building could look like this:
| Category       | Floor height | Floor count |
|----------------|--------------|-------------|
| Offices        | **           | *           |
| Services       | **           | 2           |
| Garage parking | 4            | 2           |

\* Filling section (no floor count)
\** Floors with height defined by the selected category
Filling section will simply fill the remaining height of the Rhino object with floors of given category. That way this category will work for building of any size.

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