Frontend Interaction

For debugging purposes, the following key events are implemented in the QUARREE100 example project:

One can alos interact witht eh frontend using the mouse with keys L,M,R.

Grid & Tiles

image of grid representations: photo of acrylic tiles, webcam stream from underneath, software representation in frontend

The grid objects are initialized in q100viz/ They are software representations of the physical grids’ configuration and define how elements shown on the aerial map are to be displayed.
for grid_, grid_udp in [[session.grid_1, grid_udp_1], [session.grid_2, grid_udp_2]]:
  udp_server = udp.UDPServer(*grid_udp, 4096)
  udp_thread = threading.Thread(target=udp_server.listen,

In the frontend code of our example, there are two grid objects, each representing a grid on one of the physical tables. Each of them starts a new thread to receive UDP messages with information on the grid cells’ ids and their (absolute and relative) rotation

All cells have an ID that can be any number ranging from 0 (corresponding a tangible with a white underside) through 5 (codes on the underside). Once a cell gets an ID that is not 5 (white), it is considered to be “selected”. As a result, a broader frame will be drawn around it (see image above). Then it can be addressed via one of the sliders, information on the object will be displayed on the infoscreen, certain functions can be triggered upon selections, such as mode switching.


The cell’s IDs will be allocated by the tag decoder software according to a list of possible tags. The index of the corresponding tag in that list will become the cell’s ID.

Some cells can be programmed to trigger additional events, like leaving the current game mode. This is done via tables in q100viz/settings/. Read more on how to program link functions to cells here.


The grid display can be toggled using the g key. In the upper left corner of each cell, the cell’s ID is displayed. The number in the upper right corner represents the cell’s current rotation.

Grid Setup

The grid objects contain lists of cells, which can be addressed using enumeration routines:

access cells by iterating the grids
# iterate grid:
for grid in [session.grid_1, session.grid_2]:
    for y, row in enumerate(grid.grid):
        for x, cell in enumerate(row):
          # do cell operation

grid coordinates:

The positions of the cells are stored in grid.rects_transformed. This variable contains coordinates of the absolute pixel positions after their keystone-transformation on the canvas.

for i, (cell, coords) in enumerate(session.grid_1.rects_transformed):
    print("{0}: ({1}|{2}): {3}".format(i, cell.x, cell.y, coords))

# returns:
0: (0|0): [[134.9009246826172, 4.38118839263916], [134.4179229736328, 37.4811897277832], [167.75010681152344, 38.0572509765625], [168.22642517089844, 4.963389873504639]]
1: (1|0): [[168.22642517089844, 4.963389873504639], [167.75010681152344, 38.0572509765625], [201.06971740722656, 38.633094787597656], [201.53933715820312, 5.545371055603027]]
2: (2|0): [[201.53933715820312, 5.545371055603027], [201.06971740722656, 38.633094787597656], [234.37672424316406, 39.20872497558594], [234.8396759033203, 6.127132415771484]]
3: (3|0): [[234.8396759033203, 6.127132415771484], [234.37672424316406, 39.20872497558594], [267.6711730957031, 39.78413391113281], [268.12744140625, 6.708674430847168]]
4: (4|0): [[268.12744140625, 6.708674430847168], [267.6711730957031, 39.78413391113281], [300.9530334472656, 40.35932922363281], [301.4026184082031, 7.28999662399292]]
5: (5|0): [[301.4026184082031, 7.28999662399292], [300.9530334472656, 40.35932922363281], [334.2223205566406, 40.934303283691406], [334.6652526855469, 7.871099472045898]]


Grid Interaction

The grid is either updated when interacting with a computer mouse (left- right- or middle-click on the cells) or if the tag decoder detects a change in the physical grid. In the latter case, a json-formatted string is sent to the frontend via UDP and decoded in the according grid. Take a look at the code here In either case, the function gis.get_intersection_indexer is called from grid.get_intersection, checking for overlapping polygons with the selected cell.


A ModeSelector is a specific cell on the grid, which, when selected via token, activates a certain Mode.

Image of mode selectors positioned on the right side of the frontend interface.

On the right side there are four cells dedicated for the swichting of the game stages. If a non-white token is placed here, a countdown will start, after which the selected stage is entered. The countdown is implemented in order to avoid modes to be entered accidentally. As explained below, specific cell functions can be programmed using csv tables in q100viz/settings.

Programming Cell Functions

In order to create a new game mode or make a cell “do something” upon selection/interaction, functions can be allocated to cells by adjusting the tables in q100viz/settings/. All .csv files are used to assign functionality to grid cells by combining the cell’s coordinates with a certain handle and color.

A table can look like this:

grid initialization - q100viz/settings/buildings_interaction_grid_1.csv





























The handles for game mode switching have to match one of the strings defined in session.MODE_SELECTOR_HANDLES.: 'start_individual_data_view', 'start_total_data_view', 'start_buildings_interaction', 'start_simulation'. You can find more on how these “Mode Selectors” work in the according section.

valid handles are:

household-individual handles: are set in session.VALID_DECISION_HANDLES: 'connection_to_heat_grid', 'refurbished', 'save_energy'

mode selection handles: 'start_individual_data_view', 'start_total_data_view', 'start_buildings_interaction', 'start_simulation'

colors can be set using strings from this list:


The Sliders are interactive objects at the user-side of the projection. They comprise the slider itself and associated “slider handles” that define, what the slider actually does - in our use case the users can allocate one of the following functions to the slider: * the selected house will apply energy-saving measures (Yes/No bool) * the selected house will be connected to the heat grid in the year X (int) * the selected house will be refurbished in the year X (int)

The position of the physical slider is read by the tag decoder software, which sends a float between 0 (slider at left margin) and 1 (slider at right margin) to the frontend. For more details on how the camera backend processes the slider, go to the cspy section.

There is a dedicated Slider lass in q100viz/interaction/ that can be used to create slider objects. Slider objects can store information on the active slider handle and the current slider value, corresponding the phyiscal slider on the table. There are variables to define the position of the slider on the projection area. This is important for the accurate projection of features on the very position of the slider. For this, physical_diff_L and physical_diff_R are variables describing the distance FROM the left margin of the area used for slider detection in cpsy, and the distance TO the right margin of the focused area in cspy (in cm), respectively. These are set in and adapted to the sliders upon initialization.

Slider Functions


  • The Slider’s draw_controls() function will render slider handle texts and icons, as well as tool tips.

  • draw_area() draws option-specific layout onto the slider area. According to the use case, the area can either be a red/green field for binary yes/no option or show a timeline with the selection of specific year.

  • process_value(): processes incoming slider values and sets the value for the variable previously selected via the slider handles. The function is regularly executed in the grid.read_scanner_data function, which is called whenever new UDP messages are coming in from the backend. #. Check if the slider value has changed (if yes, continue) #. According to the currently active handle, change the value of the active variable using the slider’s value (and multiplicators for integers or thresholds for bools)


You can get an overview on the UDP messaging system in the frontend API section.