Rough Guide to the Atmopshere Editor – Part 2 – Sun Tab

This second part of the Rough Guide to the Atmosphere Editor will cover the first tab – “Sun” which is used for the standard, volumetric and spectral model.

The settings are pretty much identical in each of the models so this will be a relatively short episode.

Each section on the above menu will be discussed and various examples of what happens when each one is changed are given below in the hope that they will become more obvious what happens when they are changed.

Sun Colour
For the spectral and volumetric models this option is unavailable and is replaced with “Automatic Sun Colour”, this is defined by other settings which will be covered in later chapters. (Light colour and Decay of Sunlight on the “Light” tab)

The manual describes the sun colour setting as

the color map that will be used to color the sun, from outside to inside as values increase. This option enables you to create a luminous halo effect around the sun, for example.

The current setting (in the standard model is a solid yellow stripe which offers us a solid yellow sun when it is rendered.

The format for changing the sun colour is by a colour map, a gradient that decides which colour will be used based on its position within the map. To edit the colour double click or right click and select “edit colour map”. Double clicking will present you with the colour map presets,

Where as right clicking and editing the map will result in the following..

In this example I am going to use the edited colour map and create a mad sun that is red, purple and blue. This is achieved by clicking on the colour map where I want to add a colour and choosing the colour from the swatch. The end result looks as follows.

This results in a sun that looks as follows.

Almost photorealistic… but anyway, the point of this is that we can see that the colour to the right of the colour tab is in the centre of the sun and the colour at the left is on the outside.

Position Of Sun

The position of the sun relates to where the sun is positioned in the sky, the angles etc. The position that the sun is in the sky also determines how much light is present is in the scene, i.e. if the sun is low, the light is low, if the sun is high, expect highly saturated midday sun light. There are three options in this section, Azimuth, Pitch and the option to attach the sun to he camera direction.

Azimuth

An azimuth is isan angular measurement in spherical coordinates. In this case it relates to where the sun is in the sky in terms of rotation.

The starting azimuth of this scene is 0.00 degrees.

When the azimuth is increased to 90 degrees, it rotates in a anti – clockwise fashion,

right the way round to 360 degrees, the starting point.

Pitch
Relates to the position that the sun has in the sky in terms of height, from -90…

…to +90…

Attach Sun to camera direction
This option allows you to rotate the sun when the camera is rotated, for example.

With this as a starting point, if the camera is rotated 90 degrees with the option turned off the result is as follows.

Whereas with the option turned on the result is as follows.

Thanks to Bruno Memain (Of renderosity forum), Artur Rosa and Shawn Driscoll for the heads up on this.

Size of Sun
The size of the sun refers to the size of the sun, shocking really… Below are the examples of the changes made by changing the sun size in the three different models. The scaling of the sun is a little strange in that the first 30% is the only realistic times you might want to use this on the standard model as after that it is larger than the picture itself.

Standard – 0%

Standard – 5%

Standard – 10%

Standard – 25%

Standard – 40%

Volumetric – 0%

Volumetric – 5%

Volumetric – 10%

Volumetric – 25%

Volumetric – 40%

Spectral – 0%

Spectral – 5%

Spectral – 10%

Spectral – 25%

Spectral – 40%

Size of Corona
The size of the corona is an option that relates to the size of the “fuzz” around the outside ofhte sun light, a larger corona would implie that there is a greater level of haze in the sky causing the light to dissipate. This option is only availiable within the Spectral model of atmospheres.

The sun looks a little odd with no corona, but perhaps can be used to a sun a late night over the sahara or some such.

In this series of images I am using a spectral model with the size of the sun at 5% so that the changes can be seen best.

Corona Size – 0%

Corona Size – 10%

Corona Size – 25%

Corona Size – 40%

Corona Size – 60%

Corona Size – 80%

Corona Size – 100%

Sunlight masked by clouds
This is a value that relates to the amount of light that is allowed to pass through the clouds in volumetric and standard models. In order to test this model, we will have to introduce some clouds into our scene.

The manual describes this setting as..

Sunlight masked by clouds, activates the masking of sunlight by low altitude clouds. The larger the value, the more the light is masked by clouds high in the sky. Because clouds diffuse light, high altitude clouds never get to mask sunlight. This effect is automatically catered for in the more advanced Spectral model

I have used the following volumetric atmosphere and low clouds.

The results are as below.


0% Mask


25% Mask


50% Mask


75% Mask


100% Mask

Initially i was confused as to why the sunlight was not blocked by the clouds, it is important to make sure that the sun is higher than the clouds otherwise there will be no difference noticeable. The effect in this setting is only minimal, if anyone is aware of a better example please feel free to send it in and I will amend it.

Any comments or suggestions im more than happy to include them!

Part 3 is ready.