Accurate metallic car paints

Created from real world references

These are not generic car paints with changing hues – each one was created using a real world reference:

  1. Using speed shape models I had them painted in a car paint shop using real car paints, including the top coat.
  2. I photographed each painted speed shape in my own “Cornell box”, from different angles.
  3. I 3D scanned the speed shape to have the most accurate 3D reference possible.
  4. Made the virtual Cornell and inserted the 3D speed shape in the same position and angle as it was in the photograph.
  5. Started recreating each paint taking into account the hues, the strength of the topcoat, the amount and look of the metal flakes for each car paint.

The most difficult proved to be creating individual flake maps for each car paint, as the amount and spread of flakes in each paint varied considerably. Some paints have very fine flakes, others, like the Renault 926 are much rougher. It is also these flakes that give metallic car paints that distinctive look – there is a particular glow around the highlights, which depends on the amount and size of metallic flakes suspended in the paint.

The first five are: BMW 475, Citroen KMF, Fiat 611, Renault 926, VW LA7N. They can be purchased individually or as a bundle for a 25% discount.

The effect of flakes, without the flake maps

To see the individual flakes, the camera will have to be really close to the vehicle, which will not be the case in most renders. For this reason, each car paint also has a “no-flakes” version, which was carefully derived from the flakes version so they have the same type and amount of glow. The no-flakes versions look almost identical to the flakes versions, and also render clean faster. Another advantage is that you don’t have to worry about setting the right tiling on the material (see the following paragraph).

How to set the correct Global tiling based on the UVs of your geometry

Because the size of the UVs may vary from object to object, each material that uses the flake maps has a “Sizecheck” layer at the top, which simply uses a checker pattern where each checker is supposed to be 1cm big on your object.

So to determine what global tiling you should use (found in the “Override map” texture checker under the Global Properties of the material), set the checker texture in the “Sizecheck” layer to be the active viewport texture, and change the tiling of it in the texture picker until each square appears as approx. 1cm in size on your particular object. It doesn’t have to be super precise, just as long as 1 checker isn’t much bigger or much smaller than 1cm. After that, just enter the same tiling in the Override map properties.

Now the flakes will appear in the proper size on your particular object. There is also another map used as the bump for the car paint – it is found in the Topcoat and/or Grazing layers. This map uses it’s own tiling because the bump usually needs to be tiled less than the flakes map. You can also make this map visible in the viewport to see how large it will be on your object. If you find the bump to be too large, just increase the tiling of it.

Happy rendering!

Model by “Rex Fu” from Grabcad.com

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