From September 5 to 6, a summit of leaders of the G20 member countries was held in St. Petersburg; on the first day, participants were presented with a laser show, the “screen” for which was the Grand Palace and the Grand Cascade of Peterhof fountains. In order for all kinds of visual effects to look as realistic as possible, the developers needed to calculate each step with extreme precision. To perform high-precision calculations, a detailed 3D model of the building of the Grand Palace and the Grand Cascade was required.
The G20 organizers chose Trimetari to implement the laser scanning and 3D modeling project. During field work, the company’s specialists used a ScanStation P20 laser scanner from the Swiss company Leica Geosystems.
The device has a number of technical features:
– Accuracy. The scanner allows you to take measurements at a distance of up to 120 m (with a reflection of 18%) with high accuracy (1 mm) and speed (1,000,000 t/s)
— Resistant to weather conditions. Leica ScanStation P20 has a high level of dust and moisture protection (IP 54) and is the only high-precision scanner that allows you to work at temperatures down to -20°C.
— Self-calibration function. Leica ScanStation P20 has the ability to calibrate the device without the intervention of a service center.
Work on the project consisted of two stages: field and office.
1. Field stage – laser scanning of part of the facade of the Grand Palace, overlooking the Lower Park, the Grand Cascade. The shooting was carried out in a conventional system of coordinates and heights. The field stage was completed in 1 day. Peterhof is a popular tourist destination; the large number of visitors to the museum has resulted in some difficulties. Dense flows of people not only limited the visibility of the building’s facade, but also blocked the marks that were used to stitch the scans into a single coordinate system. For this reason, the stamps were posted with greater density and, if possible, taller than human height; the total number of stamps was about 100 pieces. At the stage of field work, the stamps were not scanned separately in the field, but were recognized in desk mode using the Leica Cyclone software.
A total of 16 positions of the device were made. This quantity made it possible to cover the entire necessary shooting area. At each point, 360° scanning with a resolution of 3 mm at 10 m and panoramic photography were performed. As a result of field work, a point cloud and panoramic photographs were obtained, from which point clouds can be colored in real colors. With a scan detail of at least 1 point per 1 cm2, the resulting accuracy was estimated at 1 cm (SKP).
2. Office processing. At the processing stage, scans were registered and a 3D model of the facade and cascade was built. The result of the work was presented in the form of a point cloud in ASCII TEXT (XYZIRGB) format and a 3D triangulation polygonal model. In accordance with the technical specifications, the facade walls, projections, the visible part of the roof, pediments, and a fragment of the 3D model were modeled.
pilasters, window, doorways, external part of window fillings. The modeling process itself consisted of inscribing geometric primitives into a point cloud. Sculptures and other elements of complex shapes were modeled using tools that covered the point cloud with TIN surfaces. The result of the modeling was a 3D triangulation model in OBJ format.
The 3D model was used to create a laser show that was unique in its scale. For video mapping, 18 powerful projectors were used, which displayed the image on a façade 293 meters long.