Veil – Cathedral

A sphere of light 20 metres high in the apse of a church nave

VisualisationMuseumFree spatial study

Visualisation of a fictional space – not a realised project.

A church nave 100 metres long and 45 metres high. In the apse, “Spalten” from the Veil series hovers – two projections one above the other, 18 × 20 metres, a sphere of light in the darkness of the vault.

Two rows of piers lead the eye to the apse wall, transverse arches articulate the vault, and tall clerestory windows remain dark at night. The work is shown in portrait format: two landscape images one above the other, with the bottom edge at four metres. Because the work stands on a black ground, one reads not a screen but an object hanging freely in space.

Visitors stand in the central nave and between the piers; the pews remain at the back. The cool light of the sphere grazes the piers and floor and hints at the depth of the nave – a work that does not fill the space but condenses it.

Technical details

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

Upper row: One Barco QDX-4K45 projector with R9862001 TLD+ 90° ST lens (0.65-0.85), 0.67-0.88 on the QDX-4K, 45,000 lumens, hangs from a cross truss. The image measures 18.00 × 10.13 m with its bottom edge at 14.13 m; the throw distance is 15.00 m (throw ratio 0.83:1, lens shift -56% vertical). Calculated luminance on the wall: approx. 79 cd/m².

Lower row: One Barco QDX-4K45 projector with R9801414 TLD+ lens (0.8-1.16), 0.86-1.25 on the QDX-4K, 45,000 lumens, stands on a floor stand. The image measures 18.00 × 10.13 m with its bottom edge at 4.00 m; the throw distance is 18.06 m (throw ratio 1.00:1, lens shift 84% vertical). Calculated luminance on the wall: approx. 79 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: church nave with two rows of piers, transverse arches and clerestory windows
Configuration: two landscape images one above the other (portrait format)
Visitors (approx.): 150

Room	Width	Depth	Height
Nave	30 m	100 m	45 m

Projection

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

1 × Projector · Upper row

18 m × 10.13 m per image

Bottom edge: 14.13 m
Distance: 15 m
Throw ratio: 0.83 : 1
Lens shift: -56 % vertical
Mounting: on the truss

1 × Projector · Lower row

18 m × 10.13 m per image

Bottom edge: 4 m
Distance: 18.06 m
Throw ratio: 1 : 1
Lens shift: 84 % vertical
Mounting: on a stand

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.

2 × Barco QDX-4K45bright enough

Luminance: 79 cd/m²
Target value: 60 cd/m²
required luminous flux: 44,659 lm
Luminous flux: 45,000 lm

Equipment

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

Barco QDX-4K45

Lens: R9862001 TLD+ 90 Grad ST (0.65-0.85), am QDX-4K 0,67-0,88
Luminous flux: 45,000 lm
Weight: 77.5 kg

Alternatives (3)

Model	Lens	Luminous flux	Luminance
Barco UDX-4K40 FLEX	R9862001 TLD+ 90 Grad ST (0.65-0.85), am UDX-4K 0,72-0,94	2 × 40,000 lm	140 cd/m²
Panasonic PT-RQ35K2	ET-D3LEW300 (Weitwinkel-Zoom)	2 × 30,500 lm	107 cd/m²
Panasonic PT-RQ35K2	ET-D3LEW200 / ET-D3LEW201 (Kurzdistanz-Zoom)	2 × 30,500 lm	107 cd/m²

Barco QDX-4K45

Lens: R9801414 TLD+ (0.8-1.16), am QDX-4K 0,86-1,25
Luminous flux: 45,000 lm
Weight: 77.5 kg

Alternatives (3)

Model	Lens	Luminous flux	Luminance
Barco UDX-4K40 FLEX	R9801414 TLD+ (0.8-1.16), am UDX-4K 0,92-1,33	2 × 40,000 lm	140 cd/m²
Panasonic PT-RQ35K2	ET-D3LEW600 (Weitwinkel-Zoom)	2 × 30,500 lm	107 cd/m²
Panasonic PT-RQ35K2	ET-D3LEW60 / ET-D75LE6 (Weitwinkel-Zoom)	2 × 30,500 lm	107 cd/m²

Price range and equipment list on request.

Drawings

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

Veil – Cathedral — Axonometric view — **Axonometric view** · not to scale

Veil – Cathedral — Floor plan — **Floor plan**

Veil – Cathedral — 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.