# blur

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## Description

The blur variation generates a filled-in circle. Unlike most variations, which transform the plane by mapping input points to output points, blur completely ignores the input. The variations blur_circle, circleblur, and sineblur also generate filled-in circles. They differ in how the density is distributed across the disk. Blur has high density in the center, gradually decreasing towards the edge. Blur_circle and circleblur have even density across the disk; they use different math, but produce identical results. Sineblur has a moderately dense center that decreases in density toward the edge.

Name: blur
Type: 2D blur

Name: blur_circle
Type: 2D blur
Author: Joel and Michael Faber

Name: circleblur
Type: 2D blur
Author: Anton Liasotskiy (zy0rg)

Name: sineblur
Type: 2D blur
Author: Anton Liasotskiy (zy0rg)

The blur variation lends its name to a whole class of variations that, like blur, ignore their input. Some of these have “blur” in their name, such as nBlur and radial_blur. But most do not; some popular ones are crackle, dc_perlin, and parplot2d_wf. Somewhat confusing, several variations that have “blur” in their name transform their input to make it blurry, so are not in the class of blur variations; examples are blur_linear and farblur.

Most blur variations have sharp edges and are not “blurry” by themselves. However they do add blur when added to a transform with normal variations. For example, the top image is a simple spherical gasket. In the bottom image, a tiny amount (0.001) of blur was added to one of the transforms. This technique is often used to soften sharp edges in fractal flames.

Blur variations are often used to fill in holes in a flame. For example, the gasket above has lots of circular holes that are just waiting to be filled. In this case, just one hole needs to be filled; the fractal structure will replicate the filling to all the other holes. Here we put a sineblur in the hole just to the left of the center.

When working with blurs it’s important to realize that since the input points are ignored, the pre-affine transform will have no effect. To move the blur, as we did the sineblur above, the post transform must be used.

Blur variations can also add design elements to a flame. Here, blur_circle creates circles that add interest. Other blurs create different shapes; for example, starblur creates stylized stars and radial_blur creates starbursts.

Blur variations are essential for many styles of flames. They provide a basic shape that is then repeated and distorted by other transforms. For example, the plastic style uses blur to create a circle on one transform, then spherical with just a touch of linear on another transform to form the plastic style. The bright spot from blur is typical of this style; replacing it with sineblur gives the plastic shapes a matte appearance. Using other blur variations gives different results (some pleasing, some not so much).

Another useful technique is to duplicate the blur and change the variation in the copy to a normal variation, preferably one with the same shape, such as bubble or eyefish for blur. This adds some texture taken from the rest of the flame to the circles. Adjust the pre-affine transforms, which work for non-blur variations. Here is what happens when the duplicate is replaced with hemisphere. Alternatively, the blur can be simply replaced with a normal variation; here, that would eliminate the bright spots at the centers of the circles, which add to this flame. But every flame is different; there are no hard rules. Experiment!