Specular reflection model in computer graphics


The Phong Model, Introduction to the Concepts of Shader

8.13.2018 | Sydney Jenkin
Specular reflection model in computer graphics
The Phong Model, Introduction to the Concepts of Shader

For now, let's focus on the specular function itself. Figure 2: the waves of this water surface breaks the reflection of the background scene. Bui Tuong Phong was a promising researcher in the field of computer graphics who sadly past way in 1975 soon after he published his thesis in 1973. One of the ideas he developed in.

Figure 1: the specular highlights are just a reflection of the strongest sources of light in the scene surrounding the ball. The ball is both diffuse and specular (shiny).

From there, it will become easier to generalise the technique which is what the concept of BRDF and illumination or reflection model are all about. Before we dive into the concept of BRDF and illumination model, we will introduce a technique used to simulate the appearance of glossy surface such as a plastic ball for instance.

There is an exception to this rule though with metals.

Phong reflection model

9.14.2018 | Ashley Lamberts
Specular reflection model in computer graphics
Phong reflection model

The Phong reflection model is an empirical model of the local illumination of points on a surface. In 3D computer graphics, it is sometimes ambiguously referred to as "Phong shading", in particular if the model is used in combination with the interpolation method of the same name and in the context of pixel shaders or other.

The Phong reflection model in combination with Phong shading is an approximation of shading of objects in real life. Inverse refers to the wish to estimate the surface normals given a rendered image, natural or computer-made. This means that the Phong equation can relate the shading seen in a photograph with the surface normals of the visible object.

Which can be rewritten for a line through the cylindrical object as:

Furthermore, the value λ can be approximated as λ = ( R ^ m − V ^ ) ⋅ ( R ^ m − V ^ ) / 2 {\displaystyle \lambda =({\hat }_ -{\hat })\cdot ({\hat }_ -{\hat })/2}, or as λ = ( R ^ m × V ^ ) ⋅ ( R ^ m × V ^ ) / 2.

Specular reflection

10.15.2018 | Mackenzie Young
Specular reflection model in computer graphics
Specular reflection

Specular reflection, also known as regular reflection, is the mirror-like reflection of waves, such as light, from a surface. In this process, each incident ray is reflected, with the reflected ray having the same angle to the surface normal as the incident ray.

A classic example of specular reflection is a mirror, which is specifically designed for specular reflection.

Reflectivity is the ratio of the power of the reflected wave to that of the incident wave. In regions of the electromagnetic spectrum in which absorption by the material is significant, it is related to the electronic absorption spectrum through the imaginary component of the complex refractive index. The electronic absorption spectrum of an opaque material, which is difficult or impossible to measure directly, may therefore be indirectly determined from the reflection spectrum by a Kramers-Kronig transform.

Phong Model

11.16.2018 | Ashley Lamberts
Specular reflection model in computer graphics
Phong Model

Phong Model for Specular Reflection. Specular reflection is when the reflection is stronger in one viewing direction, i.e., there is a bright spot, called a specular highlight. For an ideal reflector, such as a mirror, the angle of incidence equals the angle of specular reflection, as shown below.

For color there will be versions of the above equation for Red, Green, and Blue components. The assumption is often made that the specular highlights are determined by the color of the light source, not the material, e.g., ksR = ksG = ksB = 1.0 This is true of plastic which is why many computer graphics images appear to be plastic. The coefficient of specular reflection ks is usually not the same as the coefficient of diffuse reflection kd or the ambient reflection ka.

Reference.

Phong observed that for very shiny surfaces the specular highlight was small and the intensity fell off rapidly, while for duller surfaces it was larger and fell off more slowly.

Caustics and specular reflection models for spherical objects and

4.9.2018 | Mackenzie Young
Specular reflection model in computer graphics

Caustics and specular reflection models for spherical objects and lenses. Authors This paper proposes an algorithm to render reflected and refracted “light” rays for spherical objects and lenses. Indirect 1.3.7 Computer graphics: Three-dimensional graphics and realism-shading, shadowing General terms: algorithms.

CR Categories and subject description: 1.3.3 Computer graphics: Picture/image generation-display algorithms. 1.3.7 Computer graphics: Three-dimensional graphics and realism-shading, shadowing General terms: algorithms.

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In the case of a convex lens, light rays become extremely directional and light energy increases. The proposed algorithm is limited to a collimated light ray and does not account for the case of dispersed light. The dispersed light has low intensity which may be insignificant for the illumination calculations. The refracted light is noticeable as a focal point for a convex lens, and as dispersed light in a concave lens. Reflected light may be considered an additional light source; if it is included in the intensity calculation, indirect illumination can be rendered. This paper proposes an algorithm to render reflected and refracted “light” rays for spherical objects and lenses. Ray tracing is a most powerful and elegant rendering technique and is able to render shadows, reflections, and refractions very nicely. However, reflections and refractions in ray tracing simulate the reflected and refracted “eye” ray and not the “light” ray. Standard ray tracing techniques therefore suffer from a lack of specular interreflection and caustics. The result appears as caustics. Indirect illumination is a result of the reflection of light rays.

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December 1986, Volume 2, Issue 6, pp 379–383| Cite as.

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