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69 lines
2.8 KiB
Markdown
69 lines
2.8 KiB
Markdown
# Visibility Ranges (HLOD)
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This demo showcases how to set up a hierarchical LOD system using visibility ranges.
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This can improve performance significantly in 3D scenes by reducing the number of
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draw calls and polygons that have to be drawn every frame.
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Use WASD or arrow keys to move, and use the mouse to look around. Press
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<kbd>L</kbd> to toggle the use of visibility ranges. Press <kbd>F</kbd> to
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toggle the fade mode between *transparency* (the default in this demo) and
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*hysteresis* (which is slightly faster, but results in more jarring
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transitions).
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> **Note**
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>
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> Performance is expected to decrease significantly after disabling visibility ranges,
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> as all trees will be drawn with full detail regardless of distance.
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Language: GDScript
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Renderer: Forward Plus
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## How does it work?
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There are 2 goals when using visibility ranges to improve performance:
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- Reduce the number of polygons that need to be drawn.
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- Reduce the number of draw calls, while also preserving culling opportunities when up close.
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To achieve this, the demo contains four levels of LOD for each cluster of 16 trees.
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These are the levels displayed from closest to furthest away:
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- Individual tree, with high geometric detail.
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- Individual tree, with low geometric detail.
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- Tree cluster, with high geoemtric detail.
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- Tree cluster, with low geometric detail.
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When the distance between the camera and the tree's origin is greater than 20
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units, the high-detail tree blends into a low-detail tree (transition period
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lasts 5 units).
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When the distance between the camera and the tree's origin is greater than 150
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units, all low-detail trees in the cluster are hidden, and the trees blend into
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a high-detail tree cluster. This transition period lasts for a longer distance
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(50 units) as the visual difference between these LOD levels is greater.
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When the distance between the camera and the cluster's origin is greater than
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450 units, the high-detail tree cluster blends into a low-detail tree cluster
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(also with a transition period of 50 units).
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When the distance between the camera and the cluster's origin is greater than
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1,900 units, the low-detail tree cluster fades away with a transition period of
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100 units. At this distance, the fog present in the scene makes this transition
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harder to notice.
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There are several ways to further improve this LOD system:
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- Use MultiMeshInstance3D to draw clusters of geometry in a single draw call.
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However, individual meshes will not benefit from frustum or occlusion culling
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(only the entire cluster is culled at once). Therefore, this must be done
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carefully to balance the number of draw calls with culling efficiency.
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- Use impostor sprites in the distance. These can be drawn with Sprite3D, or
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using MeshInstance3D + QuadMesh with a StandardMaterial3D that has
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billboarding enabled.
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## Screenshots
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