Since I wrote this awhile ago, I've learned that there are other ways to set the camera X, Y, and Z position for the population(s) of models such as placing your mouse over the preview window to a spot where you might like; do a 'copy' and 'paste' this into your 'area centre'. Then, you may want to use the 'distribution shader' to control altitude and/or slope limits where you want the population to appear.
Anyhow, hope you can benefit from this tutorial I wrote for myself:
Object (.obj) and Terragen Object (.tgo) Populations; also, Single object placement
Preface
Many times, what I like to do is open up Terragen and have a look at the plant and all of its components I'll be using. You can do this without having a scene set up. Just open up Terragen; go to 'add object'; and, make your selection as a 'single object'. Now, open your mouse maneuvering tool to situate your plant close to the camera (by default, right after you add the plant, it will appear at the very corner of the terrain bounding box). You can open the shader>multishader (or, shader>Parts as is the case with some models) to see all the components such as leaf, bark, etc. It is here you can select changes of diffuse color and different .jpg images that are a part of the model file. I sometimes will use my own texture files in place of the .jpg or .tif file used with the model to get better color and texture effects. You also can adjust 'specularity' (reflectivity) of each of the components while working through all the components in the multishader. Some models will say 'Parts shader'. Not confusing; just click of the symbol next to Parts shader which will bring up the components in the 'Node view'. Then going to the Node view, just double click on them to where you can make adjustments if you like.
Tutorial
Once your scene is complete, you are now ready to add some .tgo trees, flowers, bushes; or, whatever. Also, single objects wherever you want them. You should take the following steps to create a population of vegetation:
• Click on the 'Objects' tab
• Click on 'Add Object'. A side note pops open with the choice of 'Object' (for single object placement); or, 'Population'. We'll work on populations first. Place your mouse over Population and what appears are multiple choices. Select '.tgo Reader'. You have selected this because the choices of different XFrog plants are contained in the Terragen 2 program and within an XFrog folder. You probably have other plant models in your collection you would rather use. Just go ahead and make your choice of .tgo object – this process is rather intuitive and you should be able to follow the choices. One thing to remember in the back of your mind is that there are also '.obj' models that you can use within your scene; so, when you select a 'reader' (it will be usually a '.tgo reader' or sometimes an '.obj reader). It all depends how your plant model was set up by its creator.
• Let's say you're going to use an XFrog plant (these were originally .obj models but were set up by Planetside as .tgo files for your use). After you have done this, your dialog box comes up for you to make your choice of XFrog plant. Select the plant you want for the population. Conversely, if you want something else just select something from where you file all your .tgo files and make a selection.
• Once you have done this, you will note that two things show up in the white box: Pop whatever you selected 1 tgo; and, Pop whatever you selected 1 tgo/Pop whatever you selected 1 tgo.
• Click on Pop whatever you selected 1 tgo. It is here where you will begin setting up the correct parameters such that your plants will show up on the terrain. Make sure 'Enable' is checked as well as all other items.
• After reviewing the necessary inputs, start filling in the data as follows;
Unique variations: 12 or more (your choice)
Render quality: Medium (for close up scenes where the plants need more detail, you can select higher settings (click on the down arrow for more choices).
Distribution Tab
• Area Centre: Copy X and Z numbers from 'Camera'. 'Y' should be set at '0'.
• Area length 'a': 1000
• Area length 'b': 1000 Note: These a and b numbers are a matter of choice. In an extreme close up, 200 a and 200 b may be adequate. I've used 12000 a and 10000 b in large distant scenes where these settings is what was needed in order to get plant coverage where I needed it. However, render time takes quite a bit longer.
• Object spacing: This is your choice and should depend upon object scale and how dense you want the population to be. I've worked with spacing as little as 0.05 and as large as 100 – all depends on your needs.
• Click on the small box with three dots (the latest version of Terragen shows a green cross) in it and choose to add a 'Distribution shader'. Also, a great alternative to this choice is the 'Painted shader' which allows a more selective way in which to position your plants. However, for now, let's work with the Distribution shader. Follow the inputs below.
• Coverage and breakup Tab: You can start with 0.5. This number relates to the coverage of objects in the population. Experiment with it (higher; lower?).
• Fractal breakup: This is automatically checked. Use the default numbers.
• Altitude constraints Tab: What you can do here is set the Altitude minimum constraint for what the population needs. What happens, all the plants will appear from the minimum point all the way up to the top of your terrain. Conversely, if set at maximum, then the plants will appear all over from top to bottom – this is a matter of choice. Let's check the box for maximum. Max altitude should be where you want it. Run you mouse over the area in the preview window where you want to limit your population to the maximum (look at the 'Y' coordinate which is the height). This is the number you will enter for maximum altitude. Fuzzy zone is like the old Terragen in that it softens a hard sharp line of objects – you need to play with this one. Start seeing what the default number does for you. Limit minimum altitude should be un-checked; but, fill in the numbers like you did to determine them by running your mouse over the area. The same applies for this Fuzzy zone. Note: I will typically use just either min or max for altitude – not both. Likewise the same for the slope angle applies.
• Put a check in for use 'Y' for altitude.
• Slope constraints Tab: All of the inputs here are handled the same way as you did for the Altitude constraints. A check in the box for maximum (or minimum); but, do not check both. Make sure you have made all of the number readings from your mouse/over the preview window and enter the appropriate number.
• Put a check in for use 'Y' for slope.
Terrain Tab: Make sure 'Sit on terrain ' is checked.
Object scale Tab: Minimum and Maximum is your choice based on the object, point of view and many other factors ...experiment. After you run the 'populate' button, you will see if you've made your model too large or too small.
Object rotation Tab: Stay with the default numbers.
Seed Tab: Use this like you would re-seeding for different cloud patterns only this being for your object patterns.
Now, on to the next;
• Click on Pop whatever you selected 1 tgo/Pop whatever you select 1 tgo. It is here where you will continue to set up the correct parameters such that your plants will show up on the terrain. Make sure 'Enable' is checked as well as all other items.
Transform Tab: Scale is the only input you need to work with here. Try 1 – 1 – 1. You can go smaller or larger but all three numbers need to be the same. This works together with the min/max scale you entered earlier. Experiment.
Angular Position Tab: Go with the default numbers.
Surface Shaders Tab: Unless you are working with plants from a source other than XFrog, work with the default.
Leave Heading, Elevation and Distance all at zero.
Now, go back to Pop whatever you selected 1 tgo; and, at the bottom you'll see 'Populate'. Go ahead and click on it. In a few moments it will be done. Click on check box: 'Preview Instances'. You will see cubes where the plants will set. Try a cropped render of an area where the plants are to see if they show up. I will usually quick render at full size so I can get a clear view of the objects.
Needless to say, this is a bit involved; but, when you get results, it is then you will want to go back and start tweaking your settings of size, coverage, scale and etc. The more you do, the more it will become second nature to you. Finally, when you get into the Single plant placement; and, the Painted shader, drop me a message and I'll write up some procedures for you to use.
Bob
