Hanif Koh
415b17f271
The solid model is one answer to a preview that cannot keep up with a drag; a reviewer asked for the two that keep the drag view made of toolpaths. The checkbox is now a combobox, "Simplify preview while dragging", with Off, Solid model, Skip layers and Outer walls, and a spin, "Draw one layer in every N", for the toolpath modes. Off is the default, and with it nothing is built. Skip layers keeps one layer in every N. Outer walls keeps the outer and overhang perimeters of those layers, so the prime tower and supports, whose segments have other roles, drop out of it. Both keep the bottom and top layers of the visible range whole, as the solid model does, so the faces the range cuts open stay what was printed there. libvgcode takes the choice as EReducedDetailMode and a stride; the sets are rebuilt when either changes, and drawing from the reduced one is still a buffer binding. A mode change reaches the loaded preview at once, as the checkbox did.
4.6 KiB
G-code preview while dragging
The sliced preview draws every toolpath segment of the plate as an instanced box. On a large
plate that is tens of millions of segments, and the frame is GPU-bound: the cost is the number of
instances drawn, not anything the CPU does per frame. Dragging the camera over such a plate cannot
keep up. The preview_reduced_detail_mode preference (Graphics > G-code Preview, off by
default) lets the preview draw less while the user drags and put the full toolpaths back when they
let go.
| Preference | Values | Effect |
|---|---|---|
preview_reduced_detail_mode |
off, solid, layers, outer_walls |
what is drawn while dragging |
preview_reduced_detail_layer_stride |
1–20 | one layer in every N is kept by the toolpath modes |
libvgcode (src/libvgcode) builds and binds the reduced toolpath set, GCodeViewer maps the
preferences onto it and draws the solid model, and GLCanvas3D decides when the user is dragging.
The OpenGL ES path keeps a single set and ignores the preference.
Two sets, one walk
ViewerImpl::update_enabled_entities() walks the visible vertex range once and fills two segment
index buffers side by side: the full set and the reduced set (segments and options).
Building them together is what makes switching free: starting or ending a drag is a buffer
binding, never a rebuild. A change of mode or stride does rebuild. Nothing is built while the mode
is off, and the reduced buffers are then uploaded empty so that the last set does not stay
allocated.
Whatever the mode leaves out, the bottom and top layers of the visible range are kept whole: they are the faces the range cuts open, and the top is what the user is looking at.
Modes
EndLayersOnly(solidin the preference) keeps only the two end layers.GCodeViewerthen draws the sliced objects and the prime tower as opaque solids, see below.LayersOnly(layers) keeps every role of one layer in every stride.OuterWallsOnly(outer_walls) keeps the outer and overhang perimeters of one layer in every stride. The prime tower and supports have other roles and are left out.
The solid model
The preview already loads the sliced objects as shells for its translucent ghost.
GCodeViewer::render_solid_model() draws those shells opaque, in their filament colors, with the
gouraud shader, whose z range cuts them to the visible layer range. The two toolpath layers of
the reduced set are drawn afterwards and cap the cut with what was really printed there. The
shells hold only the objects, so while this mode is on the prime tower is added from its sliced
mesh, positioned as the print placed it. It is added or removed on its own when the mode changes,
without reloading the objects, keeps its opaque color so that it never appears among the
translucent shells, and stays out of their bounding box. Supports have no mesh and are not shown,
and load_shells() drops every non-model-part volume, so a negative volume is not cut out.
A plate whose shells are not loaded keeps drawing toolpaths, since the solid model would leave only the end layers.
Deciding that the user is dragging
GLCanvas3D::_update_preview_interaction() runs at the top of every preview frame, before the
canvas decides whether to reuse its cached scene, so that the switch lands in that frame. Dragging
is GLCanvas3D::is_user_interacting(), the same answer the scene cache reads: the camera, the
navigator, a gizmo, the rectangle selection or either slider being held. A slider reports this from
ImGui's active id rather than its dirty flag, which is raised and consumed inside one frame. A
wheel step has no duration, so it holds the reduced set for a 150 ms settle time instead, and the
frame that restores the toolpaths is scheduled for when that time runs out, since the render timer
only wakes the idle loop. A drag cut short by focus or capture loss is ended explicitly, and a
button release wakes the idle loop, because on some platforms nothing else would until the next
input.
Reused scene frames
GLCanvas3D keeps its last scene pass for frames that only rebuild the overlay (SceneCache). Its
key covers the canvas size, the camera and hover state, not what the toolpath sets draw, so a frame
that reuses the scene must never be one on which the set is switched.
_update_preview_interaction() therefore reports whether the bound set changed, and a frame on
which it did redraws the scene. The canvas neither captures nor reuses the scene while the user
drags, so no reduced frame outlives a drag, and the frame that ends a wheel's settle time is
requested as a full frame.