[Home]
[Edit this page]
[Recent Changes]
[Special Pages]
[Help]
Local Illumination
Local illumination models compute the color of a point on a surface by considering local properties only; the position of the point, the properties of the surface to which it belongs, and the properties of any light sources that affect it. That is, no other objects in the scene are considered - during the calculation -, neither as blocking light, nor as reflecting it. TODO-Insert-Figure-Here shows the basic data involved in the local illumination calculations.
Clearly, this is a crude approximation. For example, it will make no difference whether there is a light-blocking object between the point and the LightSource or not. In reality, the light-blocking object should produce a shadow.
However, even though the shortcomings of local illumination models are very clear, they are often used in realtime applications because they require a minimal amount of computations, and a minimal amount of data (only local data) – That is, no knowledge of other parts of the scene is required.
In the following subsections, we introduce the most commonly-used local illumination models.
Note that many of the local models here aren't ?physically-Based models. Thus, we'll loosely use the term intensity I to refer to the ?Color Intensity of a given pixel. Given that each pixel has 3 color components (red, green, and blue), there are 3 color intensities; $I_R$, $I_G$ and $I_B$. Instead of writing 3 equations – one for each component – we write a single equation with terms that are dependent on the color component subscripted with \lambda. For example, when we write
It is equivalent to the 3 equations
Next: Ambient Light
[Edit this page] [Page history] [What links here] [Discuss this topic] [Printer Friendly]
Local Illumination
Local illumination models compute the color of a point on a surface by considering local properties only; the position of the point, the properties of the surface to which it belongs, and the properties of any light sources that affect it. That is, no other objects in the scene are considered - during the calculation -, neither as blocking light, nor as reflecting it. TODO-Insert-Figure-Here shows the basic data involved in the local illumination calculations.
Basic data involved in local illumination calculation at point x:
a) Point, ?Light Source, and eye positions
b) ?Surface Normal at x
a) Point, ?Light Source, and eye positions
b) ?Surface Normal at x
Clearly, this is a crude approximation. For example, it will make no difference whether there is a light-blocking object between the point and the LightSource or not. In reality, the light-blocking object should produce a shadow.
However, even though the shortcomings of local illumination models are very clear, they are often used in realtime applications because they require a minimal amount of computations, and a minimal amount of data (only local data) – That is, no knowledge of other parts of the scene is required.
In the following subsections, we introduce the most commonly-used local illumination models.
Note that many of the local models here aren't ?physically-Based models. Thus, we'll loosely use the term intensity I to refer to the ?Color Intensity of a given pixel. Given that each pixel has 3 color components (red, green, and blue), there are 3 color intensities; $I_R$, $I_G$ and $I_B$. Instead of writing 3 equations – one for each component – we write a single equation with terms that are dependent on the color component subscripted with \lambda. For example, when we write
$I_{a\lambda} = k_{a\lambda}$
It is equivalent to the 3 equations
$I_{aR} = k_{aR}
I_{aG} = k_{aG}
I_{aB} = k_{aB}$
I_{aG} = k_{aG}
I_{aB} = k_{aB}$
Next: Ambient Light
[Edit this page] [Page history] [What links here] [Discuss this topic] [Printer Friendly]
