Question about clear objects

[dmc]

OK, so I know that the color of an object is the color of light the object reflects (ex. a red apple reflects the color red). I also know that white is when an object reflects all colors or is the absence of color and black is when the object absorbs all colors. So my question is, where do clear objects like glass fit into this? Glass doesnt absorb light so its not black, yet it doesnt reflect it either, what does it do with the light? Does the light simply pass through? If so, how is this possible?

 

[tblaxland]

Visible light passes through a material (such as glass) when that object contains no energy levels in its atoms that will absorb visible light. Such a material is not transparent at all wavelengths of electromagnetic radiation.

The light that passes through changes direction slightly, known as refraction, which is dependent on the refractive index of the material. You also get some reflection which is dependent on the angle of incidence, polarisation and refractive index. Glass also typically contains some impurities which will absorb and re-radiate light (you may notice a green colour in thick glass).

EDIT: BTW, an opaque object (ie, you can't see through it) that appears red, for example, does not selectively reflect red wavelengths. It actually scatters the red wavelengths and either reflects or absorbs the other wavelengths.

 

[dmc]

Oh ok, I see now.:speakcool: Thanks for the info.

 

[Eagle]

Turn up the mesh transparency and spectacular highlights and change the roughness to make it smooth & shiny.

Of course a completely clear object is invisible except for the distortion of light that passes through it. (Orbiter won't do distortion for you)

 

[Quick_Nick]

I've got a similar question: What about silver/reflective objects? The color silver itself (how do you 'get' it?) and also mirrors.

 

[Tommy]

Silver is a shade of light gray. What makes silver look so, well, "silvery" is it's specularity and diffusion. It reflects a lot of light, but scatters it in the process.

A mirror has high specularity and extremely low diffusion. The light "bounces" off at the same angle (from vertical) as it struck, and in the same lateral direction. The lack of diffusion makes an object "reflective", not just "shiny".

Reflectivity is very difficult to render in real time. Raytracing is one way to model reflectivity, but it's far too slow for realtime simulations. Another way is an "image map", where you essentially render the reflection first, then use it as a texture.

 

[tblaxland]

What about silver/reflective objects? The color silver itself (how do you 'get' it?) and also mirrors.

Silver (the colour) is really just a light grey colour but in a material that has high specular reflectivity. This generally occurs in metals due to their large dielectric constant. The specular component of the reflection is generally high since metals tend to have smooth finishes. So silver (and similarly gold) normally describe the combination of colour and high specular reflectivity. Mirrors are normally made of very smooth metals have very high specular reflectivity. This allows the reflected image to be seen in focus and with very little "colour cast".

Glass mirrors achieve the mirror effect by applying a metal coating to the smooth rear face of a sheet of glass. This is a fairly economical method of achieving a smooth metal surface but it does introduce some inaccuracies to the image due to the glass in front of it. Telescope mirrors have the metal on the front face and it is smoothed by a combination of fine polishing and special coatings.