13 diciembre 2013

Understanding Specularity

Understanding how surface reflectivity works in the real world is crucial for correct map authoring.
There is a way to split albedo and specular in order to get some references.
For this, all we need is a polarized light setup.

  • Camera fully manual adjusted 
  • Polarizing film for your lamp
  • Polarizer filter
  • Tripod 
  • Led lamp & remote shutter. This lamp is 6500 kelvin, producing white light.

We will take 2 photos of the subject. With and without polarizing film. Then, blend them in Photoshop with difference mode. Most of the times you will get a coloured result, so you have to desaturate the result image.




Artificial wood

Skin tests:

6 comentarios:

  1. I dont understand how the artificial wood specular map is any useful. There's no reason why it should be more specular in the middle.

    1. The wise man does not say everything he thinks, but thinks everything he says :)

    2. I can understand how it's useful in us understanding specularity, but it wouldn't be useful in practice would it?

    3. This is a method to split light and see how real world works. The result image is just a reference. If you are thinking in using these photos as texture, of course its not useful.

  2. Great stuff here once again! Tools like these and the application of them help a lot for your game rendering needs.

  3. Nice work. You could also change your setup a little and get more accurate results -

    As well as absorbing all the specular light, the filter will also absorb half of the diffuse light. That means you need to multiply the filtered image by 2 to get the full diffuse response, and subtract that from the unfiltered image to isolate the specular light.

    If you're not working with the raw images then the non-linearity of the color space needs to be taken into account too.

    It's also worth noting that the results are diffuse and specular (light), not albedo and reflectance (surface properties).