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.

Equipment:
  • 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.

Examples:

Cardboard:


Plastic-Rubber

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.

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

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

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    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.

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

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  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).

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