TG Particles 2

PARAMETERS

A Note About The Sample Images

These sample images are of a plane seen from overhead, rendered to a rather small image size, using Raycast mode with 2x Anti-Alias. To compensate, the Squares value was set lower to make the stars bigger, and the Brightness was turned up, to ensure that the stars remained visible. The results of the shader look rather better in larger images!

Listing :

  Star Noise Scale
  Star Noise Scale (thousands)
  Star Noise Type
  Star Noise Octaves
  Distribution Scale
  Distribution Noise Type
  Distribution Noise Octaves
  Min Distrib Brightness
  Squares
  Squares (thousands)
  Threshold
  Brightness
  Use UV Space?
  Star Colour
  Sky Colour

Star Noise Scale and Star Noise Scale (thousands)

Range : 0 to 999; 0 to 100

Together these set the scale of the noise used to generate the stars. The two parameters are used to allow very high values, as high values gives smaller stars and give more randomisation to the stars. At very high values, the Squares processing isn’t really required for the stars to look small and precise!

Star Noise Type

Range : 0, 1 or 2

0 is Perlin, 1 is Classic, 2 is Sparse.

Star Noise Octaves

Range : 0 to 10

Set the octaves used in the noise to generate the stars. Higher values give more detail to the noise. Note that sometimes a small value, such as 1, will help keep the stars more precisely defined.

Distribution Scale

Range : 0 to 1000

A second noise function is applied to the result to change the distribution of stars. This noise function dampens the stars when the noise value returned is low. The Distribution Scale parameter controls the scale of this noise - low values will give broad, large areas where there are no stars, and higher values will give smaller but more frequent areas where there are no stars.

Picture

Distrib Scale = 6

Picture

Distrib Scale = 1

Picture

Distrib Scale = 30

Distribution Noise Type

Range : 0, 1 or 2

0 is Perlin, 1 is Classic, 2 is Sparse.

Distribution Noise Octaves

Range : 0 to 10

Higher values give more detail to the noise. Note that higher values will result in more fading of the stars at the edges of the dark areas, whereas lower values will result in a more sudden change from light stars to the darkened area.

The image on the right shows the Distribution Octaves turned down to a value of 1 (from the default of 3). Notice how the darkened areas of stars are more sharply defined - there are less “faded” stars surrounding those darker areas, as the distribution noise has less detail in it.

Picture

Distrib Octaves = 1

Min Distrib Brightness

Range : 0 to 1

This controls how dark the darkened areas will be. At a value of 1, the distribution noise has no effect (and the processing is turned off for faster rendering). At a value of 0, the distribution noise will darken the stars completely, leaving only the sky colour. At vales in between 0 and 1, the distribution noise will darken the stars by a smoothly varying amount (so at a value of 0.5, the stars will be half as bright in the dark areas).

The sample images below show the effects of changing the Min Distrib Brightness. At a value of 0, the stars in the darkened areas disappear completely, at a value of 0.5, they are half as bright as the unmodified stars, and at a value of 1 the effects of the distribution noise are removed (and the processing turned off for faster rendering), so that you get only the effects of the Star Noise and Squares processing (this gives results somewhat similar to the original PixelNoise shader).

Picture

Min Distrib Brightness = 0

Picture

Min Distrib Brightness = 0.5

Picture

Min Distrib Brightness = 1

Squares and Squares (thousands)

Range : 0 to 999; 0 to 100

This divides the noise into squares, and is used to give stars which are precise points rather than “fuzzy blobs”. The two parameters are used to allow very high values, as on large sky spheres, there may need to be a large number of squares in order for the stars to render as precise dots. Higher values will give more, and smaller, squares.

Picture

Squares = 11

The image on the left shows the Squares value set to 11, making the squares much larger.

Note that for Raycast rendering, or when rendering to a smaller image, you may want to make the squares larger (lower values in these parameters), as otherwise the smoothing effects that occur can make the stars disappear!

Threshold

Range : 0 to 1

Only noise values above a certain amount are classed as being a star, and the Threshold parameter controls that value. A lower Threshold (of 0.3 or 0.4 say) will give more stars, and higher values will give less stars. If the Threshold is set to 0, then the result is straightforward noise from the Star Noise function.

The image on the right shows the Threshold lowered to a value of 0.5, which gives more visible stars.

Picture

Threshold = 0.5

Brightness

Range : 0 to 10

This acts as a multiplier to the brightness of the stars. At a value of 1, there is no change to the stars’ brightness. At values less than 1, the stars will be made less bright, and at values of greater than 1, the stars will be made brighter.

This can help when rendering in Raycast mode, or when rendering to a smaller output image, by making the stars more visible to overcome the smoothing effects that can happen.

Use UV Space

Range : Off or On

If unchecked, the shader used Object Co-ordinates; if checked, it uses  the UV space of the object.

Star Colour and Sky Colour

Range : RGB values

These set the colour of the stars and the colour of the sky. Note that Brightness values of greater than 1 will change the brightest colour of the stars.

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