An SOPack - Strata Tutorial

This tutorial covers all the necessary steps to apply and understand SOPack Strata - a plugin for Terragen by Sean O'Malley.

Before we continue, make sure  SOPack is installed.

Next, save the texture images below  into a single directory.  The images must be saved as bitmaps. 

To save the image as .bmp using Internet Explorer, right click on the image and select "Save Picture As...".  After selecting your directory, select "Save as type:  Bitmap (*.bmp)" at the bottom and save.

Lastly, download and unzip the World File into the same directory.

Images:
images - visit this page and save all 3 strata images, the rock texture and the height map into the same directory.  These images must be saved as or converted to bitmaps.

World File:
The Wall world file - save and unzip the world file into the same directory as the texture images.

Step 1:  World file and Terrain

We will be creating our own Terrain for this tutorial.

First though, load the world file and go to the Landscape window.  Change the terrain size to 513x513.

Next, select the large terrain creation button.  Then, draw a solid line at the top of the Terrain window.  Make it as smooth or as varied as you like.  Just make sure the line is mostly straight across.

The idea is to create a large wall that can be viewed from far away to see the entire strata effect along it.

Now that we have our terrain created, we are going to adjust the bound vertical in order to make the wall high enough to display the strata effect properly from a distance.

Click Modify Terrain and then type in the the lower value of 0 and upper value of 300 as seen on the left.  Then click Bound Vertical.   We now have a wall 300 Terragen units tall by 513 across - perfect for viewing strata.

Step 2:  Adding Strata

Lets add some strata.  We only have one surface layer - highlight it and click edit. 

Notice that under Advanced Distribution the coverage slider is all the way right and Fractal Noise is all the way left.  This is because we want the strata applied evenly to the entire terrain.  If we were using masks, this would be different.

Strata effects should always be applied using the "Tex" button found under Base Surface (the top Tex button).

Click the top "Tex" button, then click the "+" button and select "SO Strata".

You will get a window asking you to enter the minimum altitude.  We want to cover our entire Terrain which goes from 0 to 300 (from Bound Vertical above) so leave the min. altitude at 0.

Notice that the figure is in Terragen Units, not meters.

Click OK

Next is a window asking for the maximum altitude.  Type 300 so that the strata goes to the top of the terrain. 

Click OK and browse to the directory where you stored the texture bitmaps and the world file.  Select "Strata.bmp" and click OK.

When asked if you want to use a strata height map, select No for now.

Just a note - Strata bitmaps only need to be 1 pixel wide.  When SO Pack reads the bitmap to apply the strata, it uses the left most column of pixels in the bitmap. 

The taller the column, the more detail you will see in your strata.  The bitmaps I have provided are wider than 1 pixel only because that makes them easier to right click on and save.  :-)

If you render your image now, you should see something similar to the image on the left.

Not real interesting, or realistic.

Lets fix that.  First, lets add a strata height map.

Step 3:  Adding a Strata Height Map

A strata height map tells SOPack how to vary the height of the strata.  Since strata in nature are seldom straight, a subtle height map can really increase the realism of your strata. 

White parts are where the strata will be higher, dark parts are where it will be lower.  Kind of like looking at a Terragen terrain.

The height map at left is a simple one that will only vary the strata height from left to right.  This is so you can see the effect on our wall easier.

So, lets get rid of our previous strata and add a new one using a height map.

Click the top "Tex" button.  You should see SO Strata listed.  Select this and click the "X" button to get rid of our previous strata.
Repeat the previous process of adding strata, including setting the min and max at 0 and 300.  Also, still use "Strata.bmp"
This time however, select "Yes" when asked if you want to use a strata height map.  Browse to and select "Height-Map.bmp".

The next window will look something like the image on the left.

Strata deviation tells SOPack how high the strata will vary. 
In other words, the number entered will be the number of Terragen units difference between the highest and lowest points on your height map.

We have a tall wall, so lets enter 50 so we can clearly see the effect.  Click OK.

Lastly, select the size of the terrain (in this case - 513x513) and click OK.
 

If you render now, you will get something similar to the image at left.

Notice the gray area at the bottom?  This is because SOPack adds the value of the height map to the value of the strata to achieve the deviation.

To fix this, we need to subtract the maximum strata deviation from the minimum altitude.

What does all that mean?  It means we start lower.

Lets redo our Strata again.  Remove the existing strata and add a new one.
This time the Min. Altitude will be -50 (0 - 50).  Max Altitude is still 300.

Use "Strata.bmp", select Yes to use "Height-Map.bmp" as the height map, enter 50 as the max. deviation, and 513 as terrain size.

Now when you render your image, it looks like this.

We've covered the basics - next step: realism

Step 4: Adding Realism to Strata

There are 2 things that I've found help make Strata more realistic - Using the right Strata texture and adding an Overlay.

First, lets work on the strata texture.  The best way I've found to get strata colors right is to create the bitmap from a picture of whatever I'm trying to imitate.  For instance, if I'm wanting to do a picture of a desert canyon, I try to find a free picture or texture of a desert canyon wall and use a cross-section to create my strata texture. 

There are thousands of free textures on the internet created and shared for the 3D graphics community.  For this example, I am using 2 textures I found a bit ago from a free textures site (the link I had for them seems to be broken though).

The bigger (taller) the texture you use, the more detailed your strata will be.  You can cheat and stack cross sections on top of each other if you want.  Remember it only has to be 1 pixel wide.

Start by removing the previous Strata and then adding a new one.

Use a minimum altitude of -20 (this is to compensate for a deviation of 20 below)
Use a maximum altitude of 300
Select "RealStrata.bmp" as your strata texture
Click Yes you do want to use a height map
Select "Height-Map.bmp" as your height map
Use a maximum deviation of 20 - a little more subtle on our very tall wall (on real terrains I seldom use more than 15)
Select 513x513 terrain size

If you render your image, you will see something similar to this.

Not bad, but the strata lines seem a bit sharp.  I've found that typically, I get better results if I lower the contrast of the bitmap image using a paint program.

I did this to "RealStrata.bmp" and saved it as RealStrata-LC.bmp.

Remove the Strata and add a new one.  Use the exact same settings as above, but select "RealStrata-LC.bmp" as the strata texture this time.

 

Now when you render your image, it should look similar to this.

The strata is complete, but the wall needs something to break it up, to draw the eye away from the perfectly parallel lines.  This is one of the downfalls of strata, no matter how well you do it.

One solution is to add an overlay on top of the strata.

For details on adding overlays, see my Overlay Essentials tutorial.

Click on the top "Tex" button.  SO Strata should already be listed. 
(Whenever you add an overlay, make sure your strata is added first)
Click the "+" button.  Select SO Image Overlay (RGB Texture Version)
Select Overlay Type "Subtractive" and terrain size 513x513.
Tiles in X and Tiles in Y should both be set to 2.  Click OK
Select "Rock-Texture.bmp" for the texture.  Click OK.

Now, render your image. The strata effect is now complete.

A couple of notes about adding the overlay:
I used a tiling of 2 because of the size and perspective.  More just made it seem too busy and too repetitive.  Normally I use larger tiling numbers.
Subtractive was used because of the colors in the overlay.  The lighter parts of the texture correspond to the darker parts of the image.  My biggest challenge is usually in getting the strata colors and the overlay colors to work together and not be too dark or light.  Fading (lowering the contrast) of the strata and darkening of the overlay seem to work best for me.

Good luck!

Final Note

Currently, SOPack does not save any settings inside the Terragen World file.  Make sure you write down all your Strata and Texture settings before you close Terragen.  You will need to reapply SOPack each time you open Terragen.

The good news is that SOPack is currently being re-written and will be able to save (and edit) its settings very soon.

questions or comments?
email me