brompton | 3D 2D 3D

today i placed my brompton bike in its folded position into a living room. with my DSLR camera i shot 130 photos from different angles. see the image above.

i then loaded the images into autodesk reCap Photo, a program for creating 3D objects from ordinary photographs. the last experiment with a telephone went well, so i wanted to try the same process with a much more complex object.

the result was sort of a shock: instead on concentrating on the folded bike, recap had measured the whole room:

autodesk recap interpretation of 130 photos

the scene looks so real because the textures were stitched in high resolution. the photo below is no photo, it’s a 3D computer scene. the black elements are parts of the wall, seen from the outside.

[all images on this page are (c) copyrighted!]

i exported the 3D scene and loaded it into autodesk maya. it arrives with yet another surprise: we see lots of camera icons, 130 in total!

here’s a closer look at the brompton. the whole scene consists of about 5 million polygons:

once the scene is in a 3D app such as maya you are free to move around. here is a view from the top:

back in recap photo you can pre-render the scene as xray:

or in a wireframe mode; it looks almost like a pencil sketch:

using arnold as the default maya render engine, you can get results like these:

and with the scene reduced to the geometry of the bike, you can build your own environments, for example by introducing a smooth light and a reflective surface for the bike:

here you see the problems: the spokes on the rear wheel are missing, the spokes on the front wheel are visible, but they are pieces of texture, not real geometry.

from a distance like in the image above, the bike looks convincing. not so with a very close look:

computer animation, especially for gaming, is about mesh reduction. that means you don’t want so many polygons. in the screenshot below you see three bikes which look almost the same. but the left one consists of 700,000 polygons, the middle one of 140,000 and the right one of 9,000 polygon “faces”.

the wireframe visualisation tells the technical truth:

and when you remove the complex texture from the 3D structure, the poly count becomes even more obvious. in other words: you don’t need that much geometry when you have excellent textures.

if you want to get serious about modeling and animating a bicycle in 3D, the 3D scan is a good starting point. and even if you use the geometry only as a reference for modeling, you might actually appreciate the rich texture which comes with the scanning process.

i stick to the bike as it is for now. but i’ll give it a face lift ;-)

humboldt | revisited

jetzt in der wikipedia
jetzt in der wikipedia

ich hatte vor zwei jahren das kölner humboldt-gymnasium von oben fotografiert. weil es bei der geringen, dort erlaubten flughöhe unmöglich war, das ganze gelände auf ein bild zu bekommen, musste ich der drohne einen flugplan verpassen, den sie ordentlich ausführte. weil sich aber das licht während der 10 flugminuten drastisch änderte (harte schatten von der schräg stehenden abendsonne, dann wieder bewölkt mit völlig harmonisch-diffusem licht) waren die ergebnisse beim anschließenden zusammenrechnen so schlecht, dass sie für die wikipedia unbrauchbar waren. siehe → dieses klagelied.

dank verbesserter stitching-software gelang das nun, und zwar mit den 2 jahre alten fotos. entscheidend war, dass die software (in diesem fall pix4D) aus den metadaten der aufnahmen GPS- und zeitmarken herauszieht und deswegen schon vom prinzip her keine fotos an stellen legt, die geometrisch unsinnig sind, auch wenn sie optisch zu passen scheinen.

das bild oben enthält noch einige detailfehler, die man in der 8000 pixel breiten wikimedia commons-version suchen kann, aber die architektur ist völlig intakt, man kann die inspektion des dachs vornehmen, wenn man will.

inzwischen wird an der schule heftig gebaut. es sieht bald ganz und gar nicht mehr so aus, wie hier.

2D to 3D | telephone

i rendered this telephone in autodesk maya, my preferred 3D computer animation program. the phone needs a lot of cleaning up. the cable is only partly visible, there are artifacts all over the place, including that odd object in the air.

the process was this: i put the real phone on a stool which i could rotate. i shot 129 images from different angles.

129 images

then i fed the photographs into the autodesk app “recap photo” and got this result:

3D model made from photographs
side view
rear view
rotation, by autodesk recap

recap offers several export options, for example obj. here is a rendering using a standard shader in maya, the same as in the image at the very top.

rendering in arnold with two light sources

a so called “playblast” of the maya scene

in maya, when you apply the complex texture image which comes with the 2D/3D process, the mapping is perfect, but details are missing:

rendering in arnold, textured fbx

finally, i exported the 3D data as STL, which is compatible with wikipedia. you find it there now.