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I am a newbie in computer graphics and I am trying to develop a special case of path tracing really slowly! But first: I came up studying the Mitsuba renderer and one of its uses in the so-called GDPT (Gradient Domain Path Tracer). I am trying to build a Cornell Box in this framework and my silly problem arises in realizing which kind of material is a "mirror". In simpler words: I want a mirroring sphere in my scene but I don't manage to create it. According to the documentation that you can find here (http://www.mitsuba-renderer.org/releases/current/documentation.pdf) we can have all the different surfaces explained in section 8.2, which are:

  • Smooth Diffuse material (diffuse)
  • Rough diffuse material (roughdiffuse)
  • Smooth dielectric material (dielectric)
  • Thin dielectric material (thindielectric)
  • Rough dielectric material (roughdielectric)
  • Smooth conductor (conductor)
  • Rough conductor material (roughconductor)
  • Smooth plastic material (plastic)
  • Rough plastic material (roughplastic)
  • Smooth dielectric coating (coating)
  • Rough dielectric coating (roughcoating)

Can you please help me understand what set of parameters will make a mirroring surface material?

Usually for each kind of material there is a reference XML code (which is what I am using to build the scene). Therefore, the main question remains understanding how to build a mirror, but please take those examples in considerations because the parameters in those are the only things I can tune. Thanks in advance!

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  • $\begingroup$ Did you try the smooth conductor? $\endgroup$
    – joojaa
    Aug 8, 2016 at 19:46

1 Answer 1

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You want to use the "conductor" plugin to create a smooth conductor / metal type BRDF. See section 8.2.6 in the documentation.

As far as Mitsuba is concerned, a mirror is a special instance of a metal, where the material is specified as "none" (which corresponds to using complex IOR of $ \eta = 0 $ and $ k = 1 $).

Here is an example in xml:

<shape type="...">
    <bsdf type="conductor">
        <string name="material" value="none"/>
    </bsdf>
<shape>
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  • $\begingroup$ Already tried that case unfortunately.. it's the sphere on the image you can find here: imgur.com/a/2unOE . Which seems quite metal-ish but not really a mirror unfortunately $\endgroup$
    – Tarta
    Aug 8, 2016 at 23:02
  • $\begingroup$ Hm. Weird. What kind of integrator are you using to render this image? Maybe share your hole scene xml file so I can try to reproduce it? $\endgroup$
    – tizian
    Aug 8, 2016 at 23:22
  • $\begingroup$ I am using <integrator type="path"/> . I downloaded a scene from the website of the Mitsuba renderer itself, implementing a simple cornell box. I just added there my simple sphere. You can find the whole XML here (dropbox.com/s/qzjuzyg3bont7od/cbox.xml?dl=0) and at the end of the file my simple added sphere.. thanks in advance! $\endgroup$
    – Tarta
    Aug 8, 2016 at 23:29
  • $\begingroup$ Here is a rendering using your scene: dropbox.com/s/k1s825tkus2s4yk/tarta.png?dl=0 Looks good to me. Did you render the scene? Your image looks a lot like the OpenGL preview at the start... $\endgroup$
    – tizian
    Aug 8, 2016 at 23:41
  • $\begingroup$ I am ashamed..you are totally right. I thought it was already the render itself, while it was just a preview. I am sorry.. $\endgroup$
    – Tarta
    Aug 8, 2016 at 23:44

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