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Thread: Double Specular Highlights?

  1. #1

    Double Specular Highlights?

    I've modeled a contact lens and set it's surface to Dielectric for a simple glass texture. It works but I am getting specular highlights on the front surface (as I should) and also the back surface of the lens where the surface normals are faced away from the camera. The surface is not double sided so this makes no sense to me. Why am I getting double highlights?
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  2. #2
    Isn't it just refracting/reflecting the light? Play with the Refraction Index as well as Angle (in Distant Light settings). In 20119 double sided is no longer needed for glass.
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  3. #3
    Curmudgeon in Training Ma3rk's Avatar
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    Quote Originally Posted by thinkcl View Post
    I've modeled a contact lens and set it's surface to Dielectric for a simple glass texture. It works but I am getting specular highlights on the front surface (as I should) and also the back surface of the lens where the surface normals are faced away from the camera. The surface is not double sided so this makes no sense to me. Why am I getting double highlights?
    Might Glossy Reflections be ON?
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    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by Ma3rk View Post
    Might Glossy Reflections be ON?
    I donīt think that is it, if you change to area light you wouldnīt have the double reflection..normally, depends on size of area light..but, refraction will determine how the light penetrates the mesh and on to the rest of the lens and itīs curvature, if you were to add more roughness on it, you would see the specs being spread over the surface and actually describing the form of the lens and where the light hits, smaller or no rougness and you would see that decreasing to spots instead, but as mentioned..this depends on the refraction index value.

    Distant sunlight will most certainly yield double specs since it is covering a larger area while an area light will be more focused if not rescaled too much, so a couple of all these elements that balances the specularity I think.

    Test this..

    with vpr active, go from 0-2 in the refraction by dragging the slider and see how the spec changes, also ...change from distant to area light, and test rougness values.

  5. #5
    Quote Originally Posted by prometheus View Post
    with vpr active, go from 0-2 in the refraction by dragging the slider and see how the spec changes, also ...change from distant to area light, and test rougness values.
    Thanks, the refraction didn't completely eliminate the specular and roughness did but at the expense of darkening the lens and transparency. Changing to area light and increasing its size did get rid of specular. I looked at some actual photos I took of the contacts a few years ago and they do show double highlights so I guess the rendering must be accurate but for this project better they are not there at all.

  6. #6
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by thinkcl View Post
    Thanks, the refraction didn't completely eliminate the specular and roughness did but at the expense of darkening the lens and transparency. Changing to area light and increasing its size did get rid of specular. I looked at some actual photos I took of the contacts a few years ago and they do show double highlights so I guess the rendering must be accurate but for this project better they are not there at all.
    Yes, I was about to say that about double highlights probably being the case in the real world, I do use lenses mysefl from time to time and have seen various reflections going on all over, so good that the render engine behaves physicly correct if possible, and if not desired..you have to resort to set it up differently with other lightīs.

  7. #7
    Goes bump in the night RebelHill's Avatar
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    Thats not a reflection on the rear side... its just the shape of the geo. Turn off transparency altogether, I'll wager you get the same result.
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