Render Subdiv Settings
These are considered advanced settings. Usually you should not need to change them.
All of the settings on this page affect the rendering of subdivisible, displaceable surfaces, such as terrains (planets), spheres, lakes and planes. They also affect any objects where the render method has been changed to "Force Displacement". When these types of surfaces are rendered they are subdivided into micropolygons. The following settings are advanced tweaks to this micropolygon subdivision system.
Fully adaptive: This causes micropolygons to be more heavily subdivided when the surface is stretched by displacements, but reduces the amount of subdivision where the surface is compressed in screen space due to the angle of view or due to displacements. For still images this is usually a good idea, but it can lead to sudden changes between frames in an animation. Turning this OFF means that the amount of subdivision is quite regular according to the undisplaced surface, and therefore stable in animations, but doesn't give the best image quality when studying each frame separately. Big displacements will look quite faceted when this is turned off.
Force all edges: This fixes one of the problems that causes gaps between micropolygons. If two neighbouring micropolygons A and B are subdivided to different levels along a shared edge, this can cause gaps. Force all edges causes the shared edges to be subdivided to the same level. This helps in both animations and stills. However, the default is OFF because this feature has been seen to slightly increases render times. For animations, though, it's probably worth the cost to remove artefacts. The Animation Check button (on the render node's Advanced tab) will check this setting and offer to turn it ON.
Microvertex jittering: This setting is important to reduce the appearance of straight lines in some displaced surfaces. For still images we recommend you keep this turned ON. For animations, OFF seems to produce a more stable animation, but ON sometimes reduces render times by a small amount.
Detail jittering: For still images you should keep this turned ON. However, there is a mistake in the renderer that causes this to change from one frame to the next in an animation, so for animations you should switch it OFF. The Animation Check button (on the render node's Advanced tab) will check this setting and offer to turn it OFF.
Detail blending: This controls how much blending occurs between levels of detail as the distance between camera and surface changes. Blending also softens the appearance of surfaces. Higher blending values increase render time. For still images we recommend that you set this to 0 for the fastest render times. For animations we recommend values between 0.5 and 1. The Animation Check button (on the render node's Advanced tab) will check this setting and offer to set it to at least 0.5.
Displacement filter: Allows displacements to blend between levels of detail. The effect also depends on detail blending. We recommend that you keep this value at 1.
Jitter shading points: Jitter shading points chooses a random point on each micropolygon as the point where lighting and shaders are calculated. The results of those calculations are used to colour the whole micropolygon. Jittering provides a more natural image, but because of a mistake in current versions the jitter is different on each frame so it is a source of unwanted noise in animations. The Animation Check button (on the render node's Advanced tab) will check this setting and offer to turn it OFF.
Ray detail multiplier: Affects the detail of the micropolygons when they are seen by rays from the ray tracer. Those rays include reflections, refractions, GI rays, shadow rays, and everything in the GI prepass. It does not affect the detail of anything that is seen by the camera directly, except in the GI prepass. For example, if you are looking down at the bottom of a lake or river through a water surface, the lake bed or river bed is rendered using the ray tracer (rays cast from the water surface) and is affected by the ray detail multiplier, whereas the surface of the water itself is seen by directly by the camera so is not affected. Ray detail multiplier can be anything between 0 and 1. Higher values are allowed but should not be needed. "Detail" affects the size of the micropolygons. Lower detail means larger micropolygons and faster renders. If the ray detail multiplier is 1, then the micropolygons seen by the ray tracer will be at the same detail level as those seen by the camera directly. If the ray detail multiplier is 0.5, the detail will be reduced to 50% (and the size of the micropolygons will double). This settings can have a big effect on render times, so the default is 0.25. In most scenes this works very well to reduce the render time without making much noticeable difference to the image. However, sometimes you may notice a lack of detail in reflections or refractions, particularly in the lakedbed/riverbed example, and in these cases you might want to increase this number slightly. It also affects reflections, shadow rays and GI rays, but these differences are usually more difficult to see. How it affects render times: With shadows, it only affects the shadows cast by terrain or other displaceable primitives (sphere, lake, plane), but those shadows may be cast onto (received by) many other things in the scene so it may affect render times all round. With reflections and refractions it should only affect the parts of the scene where reflections or refractions are seen, but the difference in render times can be significant. It also affects the time taken to render the GI prepass, not only because many GI rays are cast during the prepass but also because that pass is entirely ray traced.
Stabilise ray detail in motion: This feature's purpose is to blend between levels of detail when calculating shadows and reflections. It aims to provide 2 benefits. First, it changes the appearance of shadows crawling across surfaces as the distance from camera changes. The crawling motion is instead replaced by a gradual blend between different shadow positions. (Unfortunately it's impossible to completely stop the shadows from changing shape, because the terrain that casts the shadows needs to change levels of detail as the camera moves.) Second, because the shadow positions are now blended instead of moving from frame to frame, this should prevent popping that occurs when shadow-casting micropolygons change their shape very close to the shadow-receiving point. Unfortunately, this feature produces artefacts of its own: sometimes a kind of cross-hatching pattern is visible. Therefore it may not be suitable for some scenes. It may also change render times.
Override size of subdiv cache:
The following applies to Terragen 4. In Terragen 2 and 3 the equivalent settings are on the Advanced tab of the Render Node
As micropolygons are generated for the ray tracer for things like shadows, reflections and GI rays, these micropolygons are stored in a subdivision cache so that they don't have to be recalculated so often. This is essential for the speed of the renderer.
Normally Terragen will automatically decide how much memory to use for the subdiv cache. It automatically chooses an upper limit based on the number of threads used to render, since more threads work better with more RAM.
If you want, you can override this upper limit. You can set the maximum size of the subdiv cache using the Size of subdiv cache in MB parameter. This controls the maximum amount of memory Terragen can dedicate to the subdiv cache.
The subdiv cache is divided up between render threads. If you set the subdiv cache so small that less than 50 MB would be used per render thread Terragen will automatically increase the subdiv cache size to the minimum of 50 MB per thread.
Since this parameter is an upper limit, most of the time Terragen will use less than this amount. However, there may be times when you want the subdiv cache to be created in it's entirety when rendering starts. You can use the Preallocate subdiv cache checkbox for this.
Setting the subdiv cache size too large can unnecessarily use up memory, taking it away from other needs such as objects, populations, and other programs on your computer. This may cause rendering to become slow or cause errors to occur. Remember that this controls only the subdiv cache, not the whole renderer.
A single object or device in the node network which generates or modifies data and may accept input data or create output data or both, depending on its function. Nodes usually have their own settings which control the data they create or how they modify data passing through them. Nodes are connected together in a network to perform work in a network-based user interface. In Terragen 2 nodes are connected together to describe a scene.
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