Minimal Sphere – Grid

One work on four projections, twelve metres wide, in a high hall with a gallery

VisualisationMuseumFree spatial study

Visualisation of a fictional space – not a realised project.

“Schwelle” from the Minimal Sphere series fills the end wall of a ten-metre-high hall: four projections in a two-by-two grid form an image of twelve by just under seven metres.

The work is not divided into strips but enlarged as a whole and laid across four projectors that meet seamlessly at the edges. The bottom edge is at one and a half metres, the top edge above eight metres – the image becomes architecture.

A gallery at a height of four and a half metres runs along the rear wall, reached by a staircase. From below, one stands before the sphere as before a wall; from the gallery, one sees it at eye level, together with the space beneath and its visitors.

Technical details

What it takes to build this space: dimensions, equipment, brightness.

Upper row: Two Panasonic PT-MZ882 projectors with ET-ELW22 lenses (short-throw zoom), 8,200 lumens each, hang from cross trusses. Each partial image measures 6.00 × 3.38 m with its bottom edge at 4.88 m; the throw distance is 4.80 m (throw ratio 0.80:1, lens shift -68% vertical). Calculated luminance on the wall: approx. 129 cd/m².

Lower row: Two Panasonic PT-MZ882 projectors with ET-ELW22 lenses (short-throw zoom), 8,200 lumens each, hang from cross trusses. Each partial image measures 6.00 × 3.38 m with its bottom edge at 1.50 m; the throw distance is 5.40 m (throw ratio 0.90:1, lens shift -168% vertical). Calculated luminance on the wall: approx. 129 cd/m².

Alternatives, price range and all dimensions per device are listed in the equipment list; floor plan, section and axonometric view show the projection cones.

Room

The room of the scenario and how the images are placed in it.

Room: high hall with gallery and staircase
Configuration: whole image enlarged across 2 × 2 projectors

Room	Width	Depth	Height
Hall	18 m	14 m	10 m
Gallery	18 m	4 m	5.5 m

Projection

How the images are created: equipment, image size, distance and mounting.

2 × Projector · Upper row

6 m × 3.38 m per image

Bottom edge: 4.88 m
Distance: 4.8 m
Throw ratio: 0.8 : 1
Lens shift: -68 % vertical
Mounting: on the truss

2 × Projector · Lower row

6 m × 3.38 m per image

Bottom edge: 1.5 m
Distance: 5.4 m
Throw ratio: 0.9 : 1
Lens shift: -168 % vertical
Mounting: on the truss

All partial images belong to one picture – one computer outputs them simultaneously and frame-accurately.

Real time and interaction

The film shows a recording. In the installation the work is computed live – and can respond to the space and its visitors.

Computation: live, in real time, on a high-end computer with a powerful 3D graphics card, NVIDIA RTX 4070 or higher; with many image surfaces also with several graphics cards
Output: all projectors in a room from one computer, as coordinated zones rather than separate videos
Interaction: 3D LiDAR scanners capture people and movement in the space; the work can respond to them
Fitting: mapping to the actual architecture – edges, columns, ceilings and floors

Brightness

Whether the image will be bright enough: luminance achieved against the target value. The line in the bar marks the target value.

4 × Panasonic PT-MZ882bright enough

Luminance: 129 cd/m²
Target value: 60 cd/m²
required luminous flux: 4,962 lm
Luminous flux: 8,200 lm

Equipment

The reference devices used for the calculations. Devices of the same class are equally suitable.

Panasonic PT-MZ882

Lens: ET-ELW22 (Short-Throw-Zoom)
Luminous flux: 8,200 lm
Weight: 18.6 kg

Alternatives (3)

Model	Lens	Luminous flux	Luminance
Barco G62-W9	R9801840 G lens 0.75-0.95:1 (Short Throw)	9,500 lm	149 cd/m²
Panasonic PT-REZ15	ET-C1W400 (Weitwinkel-Zoom)	15,000 lm	236 cd/m²
Panasonic PT-RQ35K2	ET-D3LEW300 (Weitwinkel-Zoom)	30,500 lm	479 cd/m²

Price range and equipment list on request.

Drawings

Axonometric view, floor plan and section show the space and the projection cones.

Minimal Sphere – Grid — Axonometric view — **Axonometric view** · not to scale

Minimal Sphere – Grid — Floor plan — **Floor plan**

Minimal Sphere – Grid — Section — **Section** · not to scale

Glossary

Real time: The image is recomputed at every moment, about 60 times per second, instead of being played back as a finished video.
3D LiDAR scanner: Scans the space with laser light and captures people and movement in three dimensions – the basis of the interaction.
High-end computer: A computer with a powerful 3D graphics card – NVIDIA RTX 4070 or higher – that computes the image live and drives all projectors at once.
Mapping: Fits the projection to the actual geometry of the space so that image and architecture meet exactly.
Throw ratio: Distance divided by image width. At 0.8 : 1, the projector for an image 6 m wide stands 4.8 m away.
Lens shift: Shifts the image within the lens without tilting the projector – so it stays rectangular.
Luminous flux: How much light the projector emits, in lumens.
Luminance: How bright the image surface appears to the eye, in candelas per square metre. In a dark room, about 60 is enough.
Bottom edge: The height of the bottom edge of the image above the floor.
Synchronised output: Several projectors show parts of the same image; one computer outputs them simultaneously – computed live or as video.