Can someone please explain what are the 3 types of light reflection from surfaces in the Phong Lighting Model?

Maybe possibly using a diagram to help me understand it better?


1 Answer 1


The three types you are referring to are specular, diffuse and ambient reflection. I find the example image on wikipedia to show the individual parts quite nicely:

enter image description here

First the ambient light is showing. This is not really a reflection, but more of a way to make up for global illumination in a cheap way. You simply assume that a small portion of light is always reaching every point on your object, no matter where that object is or how its positioned. Even when standing on the ground, the parts that touch the ground are lighted here. Because the light is the same everywhere, you can't even tell if it is a 3D object or just a drawing.

Next is the diffuse reflection. This is an approximation of light that enters your object, bounces around a bit and leaves the object again. Naturally, more light reaches surfaces that are angled "towards" the light, this is why in the image you can see shadows in the left pointing parts but increasingly more light on the right pointing parts. Due to the bouncing within the object, the exit direction of the light is somewhat random, therefore no concentrated highlights are created.

Highlights you can see are the specular reflection in the third image. Specular reflection is that part of light, that reaches the object and immedeately bounces of it again. Thereby it keeps most of the light (from the same light source) directed into more or less the same direction, thus the highlights.

The last part of the image is everything combined, giving you a nice and cheap approximation of real light.


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