Texture displacement: animations that play on their own, and art for the

rest of the panel

The animations advanced one frame per mouse movement and stood still
whenever the mouse did. schedule_extra_frame() only guarantees an idle
event at the moment the next frame is due; GLCanvas3D::on_idle() returns
without rendering anything unless something marked the canvas dirty by
then, and nothing had. set_dirty() on the gizmo is what on_idle reads,
through GLGizmoBase::update_items_state(), to find out there are frames
still to draw.

Thirty-odd more pictures, covering the paint tools, brush size, the
connected-area fill, the five views, the five projections, subdivision,
feature-adaptive refinement, remeshing, hard edges, slivers, geometry
smoothing, filament mixing and denoise.

The generator grew three more drawing languages beside the shaded relief,
each picked by what the setting is rather than by taste: a flat mesh of
triangles where the subject is the mesh or a tool, a section where the
subject is where the surface sits relative to where it was, and a flat ramp
of greys where the subject is which filament a spot ends up as. Lighting a
colour illustration or looking down on a vertical change would both add a
second thing moving between two pictures meant to differ in one.

Mapping is one ball with the checker laid on it five ways, which is the
whole of what choosing a projection does - except Unwrap, which is not a
projection onto the model and so is drawn as the flat layout it produces.

docs/HLSD/tooltip-illustrations.md

@@ -55,25 +55,45 @@ so an animation authored against that plays at the speed it was authored at.
 
 The animation restarts when its tooltip opens, rather than running off a free-running clock: these are
 short loops of one setting going from one value to another, and joining one halfway through shows the
-end of a change the user never saw the start of. The canvas only redraws on demand, so each frame asks
-for the next through `GLCanvas3D::schedule_extra_frame()`, timed to when that frame is actually due.
+end of a change the user never saw the start of.
+
+Driving the frames takes two calls, not one. `GLCanvas3D::schedule_extra_frame()` only guarantees an
+idle event at the moment the next frame is due; `GLCanvas3D::on_idle()` returns without rendering
+anything unless something has marked the canvas dirty by then, so an animation left to the timer alone
+advances one frame per mouse movement and stands still whenever the mouse does. `set_dirty()` on the
+gizmo is what on_idle reads, through `GLGizmoBase::update_items_state()`, to find out there are frames
+still to draw. The pair of them is what makes an animation play at its own speed and stop costing
+anything the moment its tooltip closes.
 
 ## Making one
 
-Captures of the real tool are the first choice for anything involving the model, the mesh or colour.
-Settings whose meaning is a shape are drawn from the same arithmetic instead, by
-`scripts/gen_texture_displacement_tips.py`: it shades a height field as a relief catching the light,
-and covers Depth, Tile, Tile size, Rotation, Repeat/Mirror, Midlevel, Smoothing, Edge fade, Invert and
-Blend that way.
+`scripts/gen_texture_displacement_tips.py` draws the lot, in four languages, picked by what the
+setting actually is:
 
-One motif - a ring inside a square frame - runs through nearly all of them, because using one shape
-everywhere is what lets two pictures be compared: whatever differs between them is the setting, since
-nothing else is.
+- **A shaded relief**, for the settings that are about a pattern: Depth, Tile, Tile size, Rotation,
+  Repeat/Mirror, Smoothing, Edge fade, Invert, Blend and the Normal, Fast, Checker and Distortion
+  views. One motif - a ring inside a square frame - runs through all of them, because using one shape
+  everywhere is what lets two pictures be compared: whatever differs between them is the setting,
+  since nothing else is.
+- **A flat mesh of triangles**, for the settings that are about the mesh or about a tool: the paint
+  tools, brush size, the connected-area fill, subdivision, feature-adaptive refinement, remeshing,
+  hard edges, slivers and the wireframe view. These carry the one accent colour in the set, meaning
+  "painted", because that is the only thing in such a picture that is not geometry.
+- **A section**, for Midlevel and for smoothing the geometry. The reason generalises: shading reads
+  slopes, so a height field moved up or down as a whole shades identically to where it started, and
+  any setting whose meaning is *where the surface sits relative to where it was* is invisible from
+  above and has to be drawn from the side.
+- **A flat ramp of greys**, for Mix filaments, Mixed colors and Denoise. Those are about which
+  filament a spot ends up as; lighting one would only add a second thing changing between two
+  pictures meant to differ in one.
 
-Midlevel is drawn in section rather than as a relief, and the reason generalises. Shading reads
-slopes, so a height field moved up or down as a whole shades identically to where it started; any
-setting whose meaning is *where the relief sits relative to the surface* is invisible in a top view
-and has to be drawn from the side, against the bare surface as a reference.
+The five Mapping pictures are one ball with a checker laid on it five ways, which is the whole of what
+choosing a projection does - except Unwrap, which is not a projection onto the model at all and so is
+drawn as the flat layout it produces.
+
+Captures of the real tool are still the first choice for anything involving a real model or real
+filament colour: Bake, the mixed-colour count on a photograph, Adjust placement, the frame window and
+the UV editor's seam tool have no picture yet for that reason.
 
 Either way: