How to use Aluminum Foil Bump Mapping Technique

This is a technique my nephew inspired while playing around with aluminum foil. In February of 2006, at the age of 16, he came over to our house and showed us how he could copy wall patterns onto aluminum foil by rubbing it on the wall with a wash rag. I said "Cool. Now can you wash the aluminum foil residue of our wall?" Being the budding Computer Scientist, he asked, "Do you think this might have a use in computer graphics?" I replied, "Well, hmmm, give my that wash rag so I can wipe the rest of that residue off our wall," and slept on it.
The next morning I awoke thinking, "Huuuhhh???, I think that little squirt might have something!!!" What follows is a technique my nephew and I developed in the early morning hours of February 24th 2006.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Aluminum Foil
• Washrag
• Flatbed Scannar
• Personal Computer
• 3D Rendering Software

1. 

   Grab some aluminum foil!

2. 

   Pull out more than enough aluminum foil to cover desired texture subject.

3. 

   Before applying aluminum foil to texture subject, take notice of matte and glossy sides of aluminum foil.

4. 

   Place aluminum foil with matte side up and glossy side down.

5. 

   Firmly rub aluminum foil with washrag over texture subject.

6. 

   Inspect quality of aluminum foil texture.

7. 

   Place aluminum foil texture on scanner window with glossy side up and matte side down.

8. 

   Scan matte side of aluminum foil texture into computer.

9. 

   Transform Foil Scan to Bump Map:
   
   In a nut shell, the bump map (normal map) is constructed utilizing vector mathematics applied to neighboring pixels from the foil map. The foil map pixel values are treated as three dimensional coordinates: (x,y,z). This is achieved by simply using the horizontal location of the pixel as the x value, the vertical location of the pixel as the y value, and the negative, normalized pixel-intensity as the z value. For example, to calculate the normal at location (x,y) in the foil map, calculate the 3D coordinates of (x,y), (x+1,y) and (x,y+1), resulting in A,B & C; convert to 2 vectors by taking the difference of the 3D coordinate pairs: V1 = B – A, V2 = C – A; take the negative, normalized cross-product of V1 and V2, resulting in N, the normal. Below is an example of the process written in C++:
   
   for (y = 0; y < FoilScan.GetHeight()-1; y++)
   {
   for (x = 0; x < FoilScan.GetWidth()-1; x++)
   {
   A = MakeVector(x,y,-GetNormalizedIntensity(FoilScan.GetRGB(x,y)));
   B = MakeVector(x+1,y,-GetNormalizedIntensity(FoilScan.GetRGB(x+1,y)));
   C = MakeVector(x,y+1,-GetNormalizedIntensity(FoilScan.GetRGB(x,y+1)));
   V1 = DifferenceVector(B,A);
   V2 = DifferenceVector(C,A);
   N = NormalizedVector(CrossProductVector(V1,V2));
   BumpMap.PutNormal(x,y,N);
   }
   }

10. 

    Once aluminum foil scan has been converted to bump map, apply bump map to 3D object(s) using 3D rendering software.

Resources

• Wavebyte Foil Mapping of Guitar Amp Surface used as Website Background
• Wikipedia on Bump Mapping
• NVIDIA on Bump Map Compression
• Wikipedia on 3D Computer Graphics Software

[sbdesign]

on 2/28/2009 Pretty cool and interesting subject. I wasn't aware of this. Thanks

[jillarieee]

on 6/10/2008 This is so cool! I can use this to imput all sorts of textures for backgrounds and details on objects.