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This option allows objects that are outside the camera frustum (i.e. objects that are not directly visible to the camera) to be tessellated to a lesser degree. The larger this valuethe factor, the lesser the this out-of-frustum tessellation will be. This setting can help save a lot of memory by tessellating "unimportant" objects less. However, sometimes an object might be outside the camera frustum but still very clearly visible through reflections or shadows. Or it might be casting a well-defined shadow within the camera frustum. For these key such objects, smaller numbers factors should be used. A setting factor of 0.0 disables this optimization. For a more detailed discussion on this, please see the relevant section below.

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In the images below, we rendered once from the camera, then we froze tessellation in the RenderView and then we "pulled the camera back" so we could see the effect of polygon tessellation for polygons outside the camera frustum. As you can see, the polygons that are inside the camera frustum are tessellated the most. The polygons Polygons that are away from the camera frustum are tesselated less and depending on the "out-of-frustum tessellation factor". The farther away a polygon is from the camera frustum, the less it gets tessellated!.


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Out-of-frustum tessellation factor: 8

16
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This setting should be used carefully! Even though a polygon is outside the camera frustum, there it might be visible through a mirror or it might be casting a very defined shadow inside the camera frustum! So, in these cases, making it tessellate very little less might make it look blocky/angular and generally too-low-poly in the reflections or the shadows!


While "out-of-frustum tessellation factor" allows us to get tessellation under control and save on Redshift's memory usage and rendering speed, there does exist one case where it might prove ineffective: scenes with large displacements and the camera being close to the displaced geometry.

To explain: When you set up displacement in Redshift, you have to declare a "maximum displacement" setting. This setting tells Redshift that displacement can go up to a certain distance. This setting is also used by Redshift when it determines whether tries to determine if a polygon is inside the frustum or outside it. The reasoning behind that is that, if a polygon is going to be displaced ("moved") by a lot, it might actually be moved inside the camera frustum, even though it was originally outside the camera frustum! . In other words, Redshift is a bit too applies "conservative" tessellation when it comes to displaced polygons that might end up being inside the camera frustum.

When this happens, Redshift might incorrectly "think" that too many polygons are inside the camera frustum and it might, therefore, tessellates tessellate these polygons a lot!

To show this, we'll edit our scene and make "max displacement" several times larger. Notice how there is much more tessellation because Redshift now thinks that all the polygons outside the frustum could possibly end up inside the frustum!

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