# What is a “Halo”?

A halo It is caused by optical effects of ice particles in suspension in the Troposphere that refract light causing a spectrum of colors around the moon or sun.(W)

The same geometry can be represented in many different ways; most of the time used to the idea of ​​an envelope surface of the graphic object for treatment; can use its constituent geometric elements, performing a selection of a reduced set them, for lighting effects.

An edge of the polygon mesh representing the object or a single vertex, can be”paint” an image synthesis. It is done in a similar way as we do with a surface.

A “halo” can be constructed from one or more effects coupled, emulating phenomena associated with light, its diffusion into the atmosphere and the production of “glitter” Special observed in different media such as movies, Fotografías etc.. that have been obtained by optical elements.

The base of the halo is based on the concepts of propagation, diffusion, reflection and refraction; light flows in each direction from a central, origen del halo.

Overall, to get the halo effect, use the vertices of geometry as small light emitting points. There are different forms of emission or propagation of light in the synthetic images that can be coupled to generate complex effects.

The vertices of the geometry seem small bulbs that give off a light that softens as we move away from the source emissive.

Halo edges fade into the background not showing “edges” separation between achieving a continuous transition.

The higher light intensity is therefore at the center of the halo.

The diffusion effect halo concentric base, can be added (or used independently) others as radio propagation.

A set of lines starting from the center and blend like spokes of a wheel, decreasing the intensity of light as they recede.

We define the number of lines and the radial distribution of the same (need not be homogeneous)

### Propagation ring

The third effect that can be added to a halo is a light propagation in rings (as shown in Figure).

The pattern shape can be varied by initial seed value or, “Seed”, that provides great variability in the creation of these rings.

Seed is known as the “seed” used to boot a system that generates numbers (pseudo) random.

A variable “Rings” determine the number of halo rings, and in conjunction with “Seed” define their final appearance.

### Propagation star

A variant of the radial propagation is the propagation in a star. The apexes thereof are positioned on the radii found earlier.

## Size

Among the variables that determine the appearance of halo we find those that affect the shape and size, well as those related to intensity, transparency, hardness etc..

The size is the most significantly influences given a concrete form, since increasing the image tends to occupy 2inundando” Same light.

## Color

The color of the point is given by the color of “Halo” Object. We will have controls to set the color of the halo, rings and straight.

If the object has a texture can also be done to influence the color, creating interesting effects of light.

### Flare (Flare)

Provides classic sparkles that occur in glass lenses. adding “vivacity” the stage.

### Rings (Rings)

Provides a number of concentric rings with different spacings (between radios) .

You can modify both the “form” rings (variable “Seed”)

as the number of rings

### Lines (Lines)

Add lines coming from the center. The number of lines can be modified and their distribution.

### Combinations of effects

As we discussed, the halo may be generated from one or more effects coupled. Look at some combinations to see variability in effect.

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Image Synthesis