Level of Detail
Dense grooms can be slow to evaluate and to draw. Level of detail is how Ornatrix App keeps the viewport responsive: it generates and draws fewer strands, and fewer points per strand, when the viewport needs the speed or when the groom is too small on screen for the difference to show. Rendering and export always use the full groom.
It has two complementary parts. The strand quality thins the hair a groom generates, so editing and display get faster without changing the groom. The LOD Switch operator lets a groom carry several versions of its hair, such as full strands and a lighter version, and passes on the one that suits the groom's size on screen.
Strand quality
The strand quality is the share of its viewport strands the Hair from Guides Operator generates. It works on top of the operator's own preview fraction: at a quality of 50%, a preview fraction of 20% shows 10% of the hair. The Detail Operator follows it too, with fewer viewport points per strand. Hair roots are generated in a progressive order, so a lower quality always shows a subset of the strands of a higher one, and the groom keeps its look as the quality changes.
The strands that remain are drawn wider, so the hair keeps its coverage. This only makes up for what the level of detail removes: hair you thinned yourself with a preview fraction is drawn at its normal width.
The quality is set from View > Strand Level of Detail:
- Strand Quality - a factor on the strands every groom generates in the viewport.
- Adaptive Strand Quality (shortcut D) - lowers the quality on its own while you make a continuous run of edits that each take longer than the Time Budget, such as dragging a slider of a heavy groom, and restores the full quality a moment after you stop. A single edit, such as one brush stroke, keeps its quality, and the groom is never refined while a mouse button is held down. Current Quality shows where it stands.
- Output Level - shows the chosen level of every LOD Switch operator instead of the one picked from the groom's size on screen. Groom Screen Size shows that size.
Render Mode (F10) and rendering always show the full groom.
Groom level of detail settings
Every groom carries its own level of detail settings, saved with it. View > Strand Level of Detail > Groom Level of Detail... opens them in the Level of Detail section of the groom properties panel. Changing them can be undone with Ctrl+Z.
- Detail Bias - a factor on the quality of this groom, for example lower for a groom that is only ever seen from afar.
- Reduce With Distance - when on, the quality is lowered as the groom gets smaller on screen, to about the share of the view it covers, in halving steps. Off by default.
- Reference Screen Size - the size on screen, as a fraction of the view height, from which the groom is shown at its full quality when Reduce With Distance is on.
- Minimum Quality - the lowest quality Reduce With Distance lowers the groom to.
- Width Compensation - how much wider the remaining strands are drawn to cover the area of those left out: 0 draws them as they are, 1 covers it all.
A groom that keeps the default settings saves exactly as before. From Python, scene.get_groom_level_of_detail_settings() reads the settings and scene.set_groom_level_of_detail_setting(name, value) changes one, undoably.
The LOD Switch operator
The LOD Switch operator passes on one of several versions of the hair, its levels of detail. Level 0 is the hair of the stack the operator sits in, the most detailed one; each hair connected to its Level Hairs input adds a coarser level, such as fewer strands, simplified strands or hair cards. Which level is passed on depends on the groom's size on screen: level 1 below Screen Size, and each further level once the size has dropped by another Screen Size Factor. Display Level pins one level whatever the size. A level whose input is not connected passes on the next more detailed one, and rendering always uses level 0.
Related
- Hair from Guides Operator - the preview fraction the strand quality works on.
- Detail Operator - viewport and render point counts.
- Hair and Guide Viewport Display - other ways to keep the viewport fast.
- Editing Groom Properties - where the groom's level of detail settings are edited.