I just received these two pictures from the glass studio Debongnie – my partner in stained-glass. A prototype-window that will be presented next week for the final of a competition.
Variations of the visual appearance of a stained glass window during the course of the sun in the sky.
[Document in French] A timeline of the visual appreance of a stained-glass, in parallel the colors of the Sunlight and the colors of the Sky, during a sunny summer day.
(PC : click-droit > “ouvrir l’image dans un nouvel onglet” pour voir l’image en grand)
(right-click > “open image in a new tab” to zoom)
Simulation of the changing visual appearance of an East-oriented Stained-glass window depending on the daylight color and orientation:
7:30 AM: before the sun rises, the sky illuminates the window
7:45 AM: a yellow Sunlight reaches the window
8:00 AM: the Sunlight is already whiter
12:00 AM: the Sunlight is white
12:30 AM: the Sunlight disappears, only the sky illuminates the window
4:00 PM: idem
6:00 & 8:00 PM: the sky’s color changes slightly
All this has been simulated using physical data about the light of the Sun and the Sky in the south of France, and physical data acquired by scanning colored glass with a spectrophotometer.
This gives you an idea of how I work. Every operation is the result of hundreds lines of code, but the logic is pretty simple. We have a quasiperiodic cristal made of triangles and we detect regular shapes (squares, diamonds, octogons, 6-gons, etc.). This creates a pattern that’s later gonna be made of little glass pieces.
With the studio Debongnie (http://vitraux-debongnie.be), we are working on a Stained-Glass prototype to be installed in a 13th Century Cistercian Abbey in the south of France. My project passed the pre-selection and we are in the final of the competition against 2 other duos artist/glass-studio.
Cistercians didn’t put colors, pictures or crosses on their windows. Their windows were supposedly « albae fiant, et sine crucibus et pricturis » (white – or colorless(?) -, and without cross and representations). Very few original 12 & 13th Century Cistercian windows survived and we know little about how they interpreted this rule.
My proposal is to produce “white light” in the Abbey, by a combination of different optical types and colors: transparent light greenish blue, light blue and light reddish blue mostly, and opalescent whites that diffuse light and are less transparent.
During the course of a sunny day, the light will vary. The visual appearance of the window will be changing a lot because of this variation.
Behind the window is a yellowish-white stone-wall. Before noon the window and the wall behind it are in the shadow. Around noon, the sun illuminates the window directly and the opal glass are becoming very bright. During the afternoon the wall behind becomes illuminated, allowing the transparent colors to appear. Finally around 4-5PM the shadow moves on the window and the opal glass stops being so bright.
GOLD + BLUE = WHITE LIGHT
Interestingly, opal glass will appear white but will project amber light on the walls or the floor of the building. The average color of the light passing through the window has been computed to be white. The glass selected last month in the factory Lamberts in Waldsassen were chosen to produce this effect, and the situation has been simulated with the light spectrum as measured last summer in the south of France.
BLUE SKY REVEALS THE COLORS
Finally, there’s the possibility of seeing the sky from an angle in the Abbey. When people will look at the window with the sky behind, it will reveal new colors again. What looked almost colorless will appear as different shades of blue and yellowish whites.
Finally, the glass version !
This is a stained glass element made with a traditional technique. The black lines are a combination of hand painted “grisaille” and lead.
I’ll soon describe the entire project in a longer post, stay tuned ;)
Next week we’ll finally be able to judge the result.
probably not accurate, but it gives a first idea.
Each unique shape that makes the map from the previous post. Total 173 unique shapes, 299 glass pieces.
This is really the result of intense work during 4 1/2 months. More news soon.
A paper model with “scanned” and calculated colors for the blue sky behind…
Below, the left one simulates a cloudy sky, the right one the blue sky
This is the design made by something like 5000 lines of code in Python 2.7 ;)
The first result of the algorithm
A & B & C : the raw material, pictures and glass transmission spectra (blue for different densities of the sheet, black for a reference white glass of the same factory)
In the previous post I showed some pictures produced by my technique of background removal for making “as accurate as possible” photos of glass sheets.
The photos were taken on a TL back-lighted, which is highly irregular. What you have to do is basically to multiply the picture A by the inverse of the picture B, after calibrating the pictures A & B together by making sure that their background has the same lightness. Of course you should do this in RAW linear 16bit!
This simple operation removes: the optical artefacts (the lens of the camera filters more light in the picture’s borders) the electronic ones (the CCD is slightly non-linear). It also automatically generates a “perfect” white balance, whatever your light source is… The only pity is that it adds some noise, but for our application this is fine.
I developed a method for selecting parts of the glass sheets based on their spectral transmission, by combining spectrophotometric measurements, math, and the corrected pictures :
The 3 zones A, B, C have an average difference of 14% in luminance when Blue-sky light passes through them.
other glass sheets characterized in the same way: