Specularity

[cyphyr]

I'm trying to adjust the specularity on a default shader but no matter what setting I choose the "hot spot" stays the same. Is this part of the reflection shader and therefore still in development or am I missing something?
By the way I don't understand how a reflective surface can have a refractive index. Surely refraction is a product of light passing through a transparent medium, not bouncing off it.
Richard

[Cyber-Angel]

See if these Wikipedia articles help

Refractive Index: http://en.wikipedia.org/wiki/Refractive_index

Refraction: http://en.wikipedia.org/wiki/Refraction

I hope these help.

Regards to you

Cyber-Angel

[cyphyr]

Thanks for the links but they don't answer the question, or rather they actually do. A material can be both reflective and refractive but only if that material is transparent. I still don't see what the point of an "Index of Refraction" is in a shader that offers no transparency.
Thanks
Richard
Ps I got round the spec hot spot problem

[Oshyan]

The relevant quote from the Wikipedia article is

Second, light reflects partially from surfaces that have a refractive index different from that of their surroundings.

- Oshyan

[cyphyr]

Err I still don't understand, I must be dim lol, but from the same quote

Two common properties of glass and other transparent materials are directly related to their refractive index. First, light rays change direction when they cross the interface from air to the material, an effect that is used in lenses and glasses. Second, light reflects partially from surfaces that have a refractive index different from that of their surroundings.

Your quote refers to transparent materials so ... can you explain further.

Thanks

Richard

[Oshyan]

As far as I understood it, it could apply to non-transparent (i.e. only reflective) materials, but it may be incorrect usage. I'll see if Matt can chime in.

- Oshyan

[Matt]

Reflective materials are often reflective because they are coated in a transparent material. The reflectivity of these materials depends on the index of refraction of the reflective coating. It affects how reflectivity changes with angle. The same is true of wet surfaces. The refractive index should be set to that of water. The default setting on the reflective shader is set to this. EDIT: In the Default Shader the default index of refraction is slightly higher (1.5), which I think is better for oily surfaces like leaves.

For other reflective materials that don't have a reflective/transparent coating, you can set the index of refraction to a high value. e.g. 10. That will result in nearly uniform reflectivity regardless of angle.

Matt

[cyphyr]

Ah that makes more sense now, particularly with reference to wet surfaces.
I am familiar with the Fresnel effect http://www.3drender.com/glossary/fresneleffect.htm where transparency diminishes with angle of incidence as reflectivity increases proportionally, I was however unaware that this was also linked to the refractive index.
Thanks for the fast reply.
Richard

[Njen]

Technically speaking, in the real world there is no such thing as specular. The specularity component of a light is a speed cheat to simply simulate reflections. Since most objects are not perfectly smooth, these surfaces will diffuse the true reflection which reduces any detail that can be noticed from a general standpoint. This generally leads to the illusion of specularity, as no real detail can be perceived in the real world.

The beveled corner of a desk, for example, may look like it has a line of specular on the edge, but it's really reflecting it's surroundings and sending the light into different directions because of the micro bumpiness of the surface.

In the real world common causes of reflective (specular) surfaces are glass, water and oils (and any product that is derived from oil - plastic, varnishes, etc). Pure metals technically do not have a diffuse component, but entirely consist of reflection. Any addition to the metal which degrades this reflective look is what causes the surface to appear less reflective. phenomena such as dust, dirt and rust can detract from metals reflectiveness. Also the smoothness of the surface of metal (like any other surface smoothness) also plays a part in how reflective a surface is perceived.

[Ogre]

You may also want to play with the Specular settings within the reflective shader.  I needed to reduce both specular settings to soften the hot spots I was getting.

[bigben]

Try reducing the tint as well. I usually set it to 0.5  That should make the reflection influenced more by what it is reflecting.