Sun through terrain
Description: You see the sun through your terrain.
Solution: Enable "Receive shadows from surfaces" in the Quality tab of the Atmosphere node.
Grainy atmosphere/clouds
Description: Sometimes you can end up with a render with grainy clouds and/or grainy atmosphere.
Solution: Generally speaking you need to determine whether you need to improve settings for clouds or for atmosphere, then adjust accordingly.
Atmosphere: If there is noise in the shadows of your terrain, whether or not there is noise elsewhere in the image, then you likely need to raise the number of samples for rendering your atmosphere.
You can find this settings in the atmosphere node under the "Quality" tab.
It defaults to 16 samples. It's best to render crops of the problem area to see when your new settings resolve the issue and to use increments of 8 samples to increase the setting.
This way you'll avoid over-usage of samples.
Clouds: If your clouds are noisy, especially in the shadowed parts or the edges, then it's likely you need more cloud samples.
You can also find this setting in the "Quality" tab of the cloud node.
It's not possible to predict how many samples you can use best, since cloud depth and density control the number of samples needed to reach a certain "detail level" which is called "Quality" in the Quality tab of the cloud node.
This quality level indicator is somewhat similar to the detail slider in the main render node, so generally speaking you can expect good results with quality at 0.8 or higher.
This is an example of the relation between cloud depth/density and the number of samples:
A cloud at a depth of 300 + density at 0.1 needs 72 samples for Quality 1.
A cloud at a depth of 3000 + density at 1 needs 664 samples for Quality 1.
You see that it makes more sense to look at the quality level rather than samples because with every project/scene your clouds will likely be different.
Conclusion: increase quality setting with ~0.2 increments until amount of grain is acceptable.
Planet-wide sea level
Description: I'd like to render a planet from orbit but I can't get full coverage of water, because the lake object doesn't match the planet's curvature.
Solution:
1) Click on the "Objects" bookmark of the network view.
2) Select node "Planet 01" which usually is your (default) planet's node name.
3) Press "CTRL+D" to duplicate your planet. You'll now see a second planet node created called "Planet 01_1".
4) Double click on the new node and find the "Surface Shader" field at the bottom.
5) At the right of the "Surface Shader" field you can see a button with a green + symbol, click on it and choose "Create New Shader -> Other Surface Shader -> Water Shader".
5) Find the radius setting in the same node, it's in the middle.
The default radius setting = 6.378e+006 metres which means 6378000 metres.
Basically you just created a spherical water surfaces with the exact same size as your "Planet 01".
You can consider this exact same size as altitude = 0 metres.
6) If you need a greater water altitude, say 100m, then set the radius of "Planet 01_1" to 6378100 metres.
If you need a lower water altitude, say -100m, then set the radius of "Planet 01_1" to 6377900 metres.
Adjust according to your needs.
Floating/non-fitting populations
Description: My populations aren't following my terrain exactly or they float.
Solution:
Upon creation of a population TG2 creates an object reader node which loads the model and a populator node which instances the objects on the terrain.
For example, if you have a rock population:
In the object tab the populator is named "/Pop Rock 01".
The object maker is named "/Pop Rock 01/Rock 01".
In the node network click on the objects bookmark.
The populator is named "Pop Rock 01"
You can find the object maker by double clicking on the populator's "+" sign at the right side of the node.
You'll go one level down the network and you'll see a new node, this is the object maker. Double click on it and you're inside the object maker.
1) Navigate to your populator node either by using the node network or the object tab at the top of the main TG2 window.
2) Open the populator node and go to the second tab called "Terrain".
3) In the "Terrain" tab check if the defined planet is matching the planet you're applying your population to.
4) In the "Terrain" tab check whether the defined "sit on terrain" shader is enabled and is not placed before your last "compute terrain" in the network. If so, set the "sit on terrain" shader to the name of the last "compute terrain" node in your network.
5) Sometimes there is displacement after the last compute terrain node. If so, then define the very last shader of your network as "sit on terrain" shader.
You can also decide to compute the terrain again and choose that as "sit on terrain" shader, but beware that it will increase rendertime and might even result in changes in your terrain/shading.
6) If none of the above helped then go to the "object maker" of your population.
7) Inside the "object maker" you'll see a "Transform" tab. Make sure that the values inside this tab are all 0 for "translate".
Values in the "translate" function will offset each instance at that value.
It is rare but possible that the object/model's "origin" is not set correctly and you'll need to (re)define the origin in another app.
For example: if the origin of the model is 1m below the basis of your tree then all your trees will float 1m above the surface. Resetting the origin to the proper position allows for correct positioning.
If you know this precise offset before-hand then you can also use TG2's "translate" values to correct this manually.
According to the previous example that would be a Y-value of -1 to move each instance 1 meter down
Restricting populations by altitude/slope
Description: I have a population that I want to restrict to specific slope and/or height of the terrain. For example, how do I prevent trees in the water and make them "stop" at the water's edge?
Solution:
It's recommended to read the section on "Floating/non-fitting populations" first to learn how to access the population's nodes.
Inside the populator you see an option "use density shader" and a button with a + symbol in to the right. Click on it and choose "create new shader -> colour shader -> distribution shader V4".
The distribution shader V4 is by default white and thus all trees will remain at the same position since the mask (mask = distribution shader = density shader) is white everywhere.
Since you want to have the population "stop" at the edge of the water you need to define a minimum altitude.
Go to the distribution shader by clicking again on that "+ button" and in the 2nd tab called "altitude restriction" you can set restrictions for altitude.
Check the altitude setting of your water object and take that value as minimum altitude value and don't forget to enable the restriction.
If your water object is at 100m altitude (default) then you need to keep an eye on the "altitude fuzzy zone" which defaults to 200m and would still allow trees to go in the water since the gradient will be from 0 to 200 metres.
For instance, set fuzzy zone to 20m and your minumum altitude to 110m and you'll end up with trees above the waterline and some pretty near it (gradient from 100 to 120 metres).
If they're still to close increase minimum altitude accordingly.
These same principles apply for restricting by slope.
Lighting/color differences in skyboxes
Description: When I render a skybox I get different lighting/exposure or visible seams among some of my rendered faces/sides of skybox.
Solution:
This problem is almost always due to use of Global Illumination (GI). GI takes samples from the scene and tries to use the contributions of all elements of the scene to render accurate lighting. For optimization reasons it only samples what is currently in view for a given render, so sometimes the calculations differ between different views of the same area since another view may show other elements which contribute to lighting.
If you persist in using GI for your clouds (as this gives best results):
1) Render at better GI settings.
If you use a GI relative detail of 1 then increase GI sample quality to 4-6.
2) Otherwise increase GI relative detail from 1 to 2 and keep sample quality 4-6.
3) It's possible there are big differences in cloud-coverage and other lighting conditions among skybox faces/sides.
Improving GI settings might not be the solution then as we need to find a way to "average" the contribution of the other faces/sides of the skybox.
If you use relatively simple clouds then it's possible you can use lower GI settings than GI relative detail 2 and GI sample quality 4-6.
In any case try the following steps with different GI settings.
In the render settings go to the "Advanced" tab.
3) You'll find a setting called "GI prepass padding" and it defaults at 0.
This setting extends the camera's frustum where in GI calculations are done.
4) Increase it's setting to 0.25. In a 1000x1000 render this means 0.25 x 1000 = 250 pixels are calculated extra outside the camera's frustum.
This way out of frustum lighting contributions are sampled too and if you do this for each face/side you'll create overlap.
5) Increase this setting with ~0.25 increments.
6) You can also try increasing GI Blur Radius from the default of 8 to something higher like 20 or 50.
If you don't care too much about GI:
Use a fill light setup.
You can find a basic fill light setup here: http://forums.planetside.co.uk/index.php?topic=580.0
When using a fill light setup make sure to disable the "Enviro Light" node and to set both GI relative detail and sample quality to 0 to completely disable GI.
There will be no visible seams when using a fill light setup!