Design custom gobos for façade mapping

Introduction

The purpose of this article is to explain some general concepts about the design of outdoor light scenarios using the gobo mapping technique, that is, the projection of custom-made images that align perfectly with the target façades to be illuminated.

PROLIGHTS has a complete range of outdoor image projectors, entirely LED and available in different sizes under the MOSAICO brand, which offers a wide set of features to enable designers and architects to create dynamic scenarios on buildings and exterior façades with great flexibility.

The Projectors of the Mosaico range stand out for their high efficiency, low maintenance cost and durable solutions, representing a winning choice also in terms of sustainability when compared to classic luminous, light or video projection signs.

Select the appropriate projector

First of all, you have to select the right projector for the application, and the choice will have to be evaluated according to some features, which can be summarised as follows: projection distance, projection angle opening, light flow emitted, available effects, complexity and degrees of detail of the images to be projected, weight and size of the device.

The summary table below summarises some of the main features and differences between the models of the Mosaico range.   

To accurately select the ideal projector, we also recommend viewing the following documentation available among the downloads of each product:

• the photometric tables in PDF format summarise, for different angles and different operating modes, the light intensity expressed in lux and the diameter of the opening beam for distances from 1m to 50m
• the photometric .ies and .ldt files, which contain the photometric data of the projectors, enable the import into software dedicated to the lighting calculation
• Use of the Dialux software (free) and the official PROLIGHTS libraries to simulate in a three-dimensional environment the coverage and intensity of the projectors on the model of the building to be illuminated. 

Gobos: standard equipment, available libraries and technical specifications

Each projector in the Mosaico range comes with a set of Gobos and standard colours pre-installed onboard the devices, ready to use to project textures and patterns.

The onboard equipment of each model can be consulted among the downloads of the website on the specific product page among the “Tech Docs” resources.

PROLIGHTS also offers a gobos & animation wheel in-house production service, with images that can be selected from a library of standard images, as well as customised images on request, for all its projectors of the Mosaico range and other families of projectors.

In order to simplify the installation by the user, PROLIGHTS provides all the gobos and animation wheels ordered separately as accessories for the Mosaico projectors already installed inside its magnetised holder.

In the event that you wish to commission a third party to produce your own custom gobos, the following table shows the specifications of the dimensions, thicknesses and materials for all the projectors of the Mosaico range.

The use of the gobo “Mapping” accessory

In order to be able to create customised images of the façades more easily, it is necessary to be able to have references in the space with reference to:

• The image of the gobos inside the projector
• The projection of it on the façade according to the desired pointing, distance and projection angle

PROLIGHTS offers – as a standard accessory for all projectors of the Mosaico range – a Gobo image called “mapping”, which, through a grid and coordinate design on X & Y axes of the projection, enables users to have references both for the image of the gobo and its projection in a relative space.

Procedure for drawing a custom gobo according to the surface mapping technique

To create a custom gobo and map it on a surface, just follow the following procedure:

1. Install the “Mapping” gobo in the projector
2. Place the projector in the exact mounting position with the chosen projection angle with respect to the façade
3. Project the “mapping” gobo on the façade
4. Take a photo of the projection site, from a point of view similar to that of the projector towards the surface to be illuminated
5. Import the photo taken in a graphic editing software (Illustrator or Photoshop) and on a new level, build the design that you intend to create
6. Import the “Mapping” graphics (.ai or .png) into a dedicated layer.
7. Prepare the file for export: use black where you don’t want lighting, use transparent where you want source light, export a vector file making only the design level visible. Send us the customised design to produce the required gobo

The download of the “Mapping Gobo” graphic in vector PDF format can be accessed among the downloads associated with each projector on the website www.prolights.it , as a file name “Mosaico_GOBO-MAPPING-DESIGN.pdf“.

A complete technical guide of the process of creating custom gobos for image mapping can be accessed among the downloads associated with each projector on the website www.prolights.it , as a file name “Mosaico_A4_GOBOS_CUSTOM_GUIDELINES(EN).pdf“.

This procedure will be more effective when the device projects with a perpendicular trajectory with respect to the projection surface, i.e. the point of light emission is central both on the X axis and on the Y axis (height) with respect to the centre of the desired projection. Under these conditions, projection distortion phenomena are negligible, and no trapezoidal (or Keystone) correction of the image design will be necessary.

Combine multiple projectors into a single image

For mapping on façades or large surfaces, it is possible to combine the projection of multiple projectors in a single image.

The procedure will be similar to the one indicated above, with the addition that the areas of intersection of projectors that overlap in projection must be taken into account.

The unique image will then have to be sectioned and divided into portions, one for each individual projector you want to employ.

Image keystone correction in angled projections

If the projector is installed in a decentralised position with respect to the projection centre (on the vertical and/or horizontal axis), to obtain a flat image, it will then be necessary to apply a trapezoidal image correction (Keystone) during the graphic development of the image to correct distortion due to angled projection.

To process the image in Keystone, the procedure indicated in the previous section must be adapted as follows:

1. On a dedicated layer within the custom graphics created, draw a vector grid using that of the photo as a reference.
2. In a new file, Import the “Mapping” graphics (.ai or .png) into a dedicated layer.
3. Overlap the custom graphics following the instructions in point 6. with the image of the “Mapping” gobo in point 7.
4. Modify the design of the custom graphics with the traced grid created in point 6. Ensure that the grid traced according to the photo overlaps with the one of the graphics of the “Mapping” gobo in point 7.
5. Prepare the file for export as indicated in the previous section.

This procedure will correct the projected image, but will not be able to correct the adjustment of the focus, as well as the different levels of intensity within the projection surface, since the points of the projection will have a non-homogeneous distance with respect to the source and its emission focus. Therefore, if possible, to obtain the best result, it is always preferable to attempt to install the projectors with a projection as perpendicular as possible to the target position.

We thank you for taking the time to read this and, as always, we do appreciate your support. For further questions on Gobo mapping technique or further information about the PROLIGHTS Mosaico range of fixtures, please feel free to contact us.