Physics/Science of Light (PART 5)

Physics/Science of Light

(How you could implement it + create dramatic compelling art scenes)

Specular Reflection:

Specular reflection is basically a mirror reflection, all the light that bounces off of the surface is being struck with a crisp reflection. In any reflection you're going to lose light, just like lambertian reflection, you lose a certain amount of light. Certain parts of the spectrum that are absorbed during this contact no longer appear visible to the viewer.

Most reflections however won't appear like a mirror reflection;

there will be quite a bit of light loss that prevents it from forming a mirror reflection.

The law of reflection:

Specular reflection abides by the law of reflection. What the law of reflection says is that the angle of incident is equal to the angle of reflection. What that means is :when light comes from the sun (or any given light source), it strikes and bounces unto the object in that scene then bounces back to the eye.

What determines the location of the reflected object is the law of reflection.

So if you were set a tangent on this ball,draw a line that is perpendicular to that point, essentially what we're able to see,that this angle 1 (label them with numbers) and angle 2, are equal. (the angles adjacent to one another)

This principal is always true with specular reflection.

What's different with the lambertian reflection as opposed to specular reflection is with a lambertian reflection we see the same reflection no matter where we go.

When dealing with a lambertian reflection, you want to keep the location of your light sources in mind, whereas with specular reflection, you don't have to worry about it.

Properties of specular light:

-specular colour (the same is true with a lambertian reflection occurence)

-incoming white light directed by the light source

When an object is affected by specular light reflection, what happens is the white light parts of the spectrum are being absorbed and some of them are being reflected. The colour of the reflection is dependent on the properties and the colour of the object.

Variable Reflectivity

With variable reflectivity you have various attributes on the object which can cause the surface to lack uniform reflectivity, such attributes can include: rust, dust, dirt buildup in the cracks, cracks, holes and so on. Most metals/ manufactured surfaces have some level of variable reflectivity. because it is usually harder to get a metal surface to be perfectly chrome.

Specular Highlights

Specular highlights are basically the brightest part of the specular reflection.

If we look at this example, the brightest part of the diffused reflection is at the very top point of the red ball.

You can see the terminus at the half way point.

You'll notice that the specular highlight is positioned below the top edge of the ball.

The location of the diffused reflection is dependent on the angle at which the light source strikes the object as well as the position that we're viewing it at.

If we're looking at the object straight on and the light is straight on that object then the specular highlight and the diffused highlight will line up exactly as shown above.

However if we're viewing the object at a different angle there will be a slight offset between the specular highlight and the diffused highlight.

If the light is behind the object we won't be able to see the diffused reflection however we'll be able to see some of the specular highlight slightly at the very tip along the edge of the object.

Anisotropic Reflection

If you examine closely, you can see the type of pattern that forms the anisotropic refection; small bubby patterns form the overall appearance of the surface. It's similar to what you'd see with brushed metal. What happens when you've got brushed metal or an anisotropic reflection is it spreads the reflection along the opposite axis of the grain.

So if the grain (of this ball) is running vertically you'll notice that the reflection will spread out in the horizontal direction.

This is an important reflection to study because it appears often in nature and in manufactured surfaces (ie. brushed metal.

Diffused Reflection

Texture is the only difference between Lambertian and Specular reflection.Generally, in reality there isn't really a difference between lambertian and specular reflection, as far as how the atoms interact with the light. However the determinative factor lies within the textures that create their characteristic surfaces.

So when there's no texture on the surface, you get a clean highly reflective mirror surface,but as the texture starts to increase you will get a spread-out blurred reflection; diffused in appearance.

And as the texture increases, the surface becomes more blurred causing the dominant highlight (at the top of the ball)to start to blur and spread out also.