Solaris is a Lighting Accessory plugin for Terragen, an excellent near photorealistic landscape generator and renderer. Solaris lets you set the sun position based on a location on the Earth, in latitude and longitude, and a date and time. Solaris requires the TGPGuiLib to run, you can find out more about it here.

Please note : Solaris currently has some pretty bad bugs in it's calculations. I debated whether I should remove it, but decided to leave it up and add a warning. The general elevation of the sun should be alright, but the direction may be incorrect depending on the location you enter. I apologise for not mentioning this earlier, and improved version should be available in a month or two.

How to use Solaris

Solaris is very easy to use. To access Solaris, click on the "Accessories" button in the Lighting Conditions window. A menu will pop up, and you select Solaris from that. Here are some screenshots of Solaris' interface. The images below are half size, click on them to see the full size version in a new window.

Mac version	Windows version

Here's a guide to the settings. Solaris verifies them and updates the final sun position in realtime as you change the settings.

• File Menu
  The File menu allows you to open and save your Solaris settings. The settings are saved in files with a .sol extension. All of the commands in the File menu should work pretty much as you expect them to, however there is a File Menu page here if you would like it explained.
  

  Solaris files are cross platform, and can be exchanged between the Mac and Windows versions.
  

• Location settings
  This is where you enter the location of interest on the Earth's surface via latitude and longitude. You enter these coordinates in degrees ( d ), minutes ( m ) and seconds ( s ) and use the popup menus to choose the appropriate directions. If your coordinate source does not specify the directions, for longitude East is positive and for latitude North is positive. You can also give the location a name.
  

• Time settings
  Hopefully this should all be self explanatory. Time is specified in hours, minutes and seconds. You do need to take into account Daylight Savings or Summer Time, and if you know that the location entered is using Daylight Savings, you should remove the amount of time you set the clock forward from the time you enter in Solaris. The GMT is the Greenwich Mean Time offset of the time zone your location is in. You must enter the correct GMT offset for your location or you will not get correct results. There is a further explanation of GMT below. The Day/Month/Year settings should be self explanatory. Leap years are handled appropriately. At this time the Year setting can not go before 0 CE ( Common Era, AD to some ). Strictly speaking the sun position algorithm is not accurate outside of a range 100 or so years either side of 1950, but in testing it has been found to be accurate enough across the entire range of allowable values ( 0 to 1,000,000 CE ) for reasonable use.
  

• Results
  This area displays the sun position according to the settings you've entered. These are the values that the sun position will be set to when you click the OK button.
  

• Cancel button
  Clicking this button closes the Solaris dialog and does not apply the sun position calculated by Solaris.
  

• OK button
  Clicking this button close the Solaris dialog and applies the new sun position calculated by Solaris.
  

Where can I find some latitude and longitude coordinates ?

There are many sites on the internet which list the latitudes and longitudes of cities and prominent places. A good place to get started is Latitude & Longitude - Look Up. A Google search for latitude and longitude should turn up many more sites.

What is the GMT setting for ?

Here's some background information on what GMT means. You don't need to know all of this, but it does help to understand what the GMT setting represents.

GMT stands for Greenwich Mean Time. It is also known as UTC, which stands for Universal Time Coordinate. The Greenwich part of GMT comes from the Royal Observatory in Greenwich, England. Many years ago, the English decided that the Greenwich Meridian ( also know as the Prime Meridian ), or 0 degrees longitude, ran through the Royal Observatory. The Greenwich Meridian essentially cuts the world in half. Due to the fact that for a long time the English were the worlds preeminent naval superpower, and longitude is crucial to marine navigation, it became a standard. As an aside, for a long time the French, who have largely had a fairly acrimonious relationship with the English over the course of history, also had their own meridian line which was supposed to represent 0 degrees longitude.

The world is divided up into 24 time zones. Each time zone has a positive or negative GMT offset from the Greenwich Meridian, depending on whether the time zone is to the East or West of the Prime Meridian. Time zones to the East of the Greenwich Meridian have a positive value, and time zones to West have a negative value. As an example, New Zealand happens to be more or less half way round the world from the UK, and so New Zealand has a GMT offset of +12 ( half of 24 is 12 ). This means that the time in New Zealand is always 12 hours ahead of the time in the UK, which is in the GMT 0 timezone ( because the Greenwich Meridian runs right through it ). For example, when it is 2 o'clock in the afternoon in New Zealand, it's 2 o'clock in the morning of the same day in the UK.

Unfortunately the timezones do not coincide with how the world would ideally be divided up into 24 slices ( imagine an orange cut into 24 "smiles" ). Some countries don't want to be divided in two by a timezone, as it would mean that one half of the country would have a different time to the other half. The USA is divided up into 4 main timezones ( Pacific, Mountain, Central and Eastern time ) which bear little relation to the ideal divisions and all of which have different GMT offsets. I imagine the divisions are along state boundaries. This is why you need to enter a specific GMT offset for your timezone, because there is no easy way for Solaris to calculate this itself based on the longitude and latitude you enter. I do hope to add this to future versions though.

In the meantime, it is important to enter the correct GMT offset for the location you're using or you will get incorrect results. If you do not know the correct GMT offset, then you should be able to find it at timeanddate.com. There are undoubtedly other places on the internet where you can find this information.

What's planned for the the future ?

Solaris is presently in it's most basic form. At this stage it is anticipated that the next version will allow you to choose from preset locations on the Earth, such as cities and other prominent places. The version after that will be what Solaris has been intended to be all along. That will let you select locations from a map of the Earth and automatically calculate time zone offsets. It is also hoped to add automatic calculation of the GMT offset.

Requirements

Mac version
When released, Solaris will run on all versions of the MacOS supported by the Mac version of Terragen. The Mac version of Solaris will be released in a month or so.

Windows version
Solaris works on Windows 95 and up. Only Terragen v0.8.44 or newer is supported. Solaris requires the TGPGuiLib v1.2, to download the latest version please visit the TGPGuiLib website.

Installation

For Mac users - Depending on which OS you are using, there are several options :

• Mac OS 8.6/9.x
  Terragen Mac loads plugins from your Application Support folder, which is inside the System Folder. To install Solaris, create a folder called "Terragen" ( no quotes ) inside your Application Support folder, if there isn't one there already. Then just place Solaris inside the "Terragen" folder and restart Terragen.
  
• Mac OS X
  Terragen Mac loads plugins from your Application Support folder. In your Home folder ( the one you go to when you click the Home button in the Finder toolbar ) there is a Library folder, and the Application Support folder is inside that. To install Solaris, create a folder called "Terragen" ( no quotes ) inside your Application Support folder, if there isn't one there already. Then just place Solaris inside the "Terragen" folder and restart Terragen. For the more Unixly inclined, the path is "~/Library/Application Support/Terragen"
  If you have sufficient permissions, you could also install Solaris inside the root level Application Support folder ( "/Library/Application Support" ), using the same steps as above
  
• Mac OS X and Mac OS 9.x
  If you happen to be using Terragen on both OS 9.x and OS X on the same machine, and the OS 9.x System Folder you use is also your Classic System Folder on OS X, then you can set things up so you only need install Solaris once. Follow the instructions above for OS 8.6/9.x. Now, next time you are using Terragen on OS X, go the Preferences and select the Plugins panel. Check the "Current Classic System folder" checkbox and restart Terragen. Your plugins will now be loaded from the same place when you are using OS X and OS 9.
  

  In all cases, if you don't mind having any other plugins you are using in the current scene removed from the scene, you can load Solaris without quitting and restarting Terragen by going to the Plugins panel of the Preferences dialog and clicking the "Reload Plugins" button.
  

For Windows users - There are two options for installing Solaris on Windows :

• If you are not already using WaterWorks or For Export Only, my two other plugins, then you need to place Solaris in the same folder your Terragen application is in. Restart Terragen and Solaris will be loaded.
  
• If you are already using one of my other plugins, then you can either place Solaris in the same folder as your Terragen application, or inside a folder called "Plugins" ( no quotes ) which is in that same folder. Restart Terragen and Solaris will be loaded.
  

  If you get an error message along the lines of "Cannot load plugin : Solaris.tgp" when you restart Terragen, then chances are you have not installed the TGPGuiLib, which Solaris requires. You can find out more about the TGPGuiLib at it's website.
  

Download

Solaris is freeware. I would appreciate it if you didn't mirror the download, at least not without asking me. I'd much prefer it if you'd link to this webpage, as it has everything a new user needs to get started. Please be aware that although Solaris is freeware, I retain all rights to it.

Solaris for Windows
Version 1.0. Released 25/4/02

Solaris for MacOS
The Mac version of Solaris will be released in a month or two.

Please note that in order to run Solaris requires the TGPGuiLib. If you do not already have this, it can be downloaded from it's website.

Support

If you have any problems, questions, feature requests or anything of that kind, feel free to contact me at jomeder@xtra.co.nz

I would like to thank Elwood Downey for developing the excellent XEphem astronomical software and making it freely available. I used XEphem to validate the results of Solaris. I used XEphem on OS X via rootless XFree86, all made so much easier by the excellent fink package manager. Thanks also to the people on the Terragen mailing list that gave me coordinates to test with.

© Jo Meder 2002, all rights reserved