The tiles moved out of the scenery's pak into an archive of their own: a
sorted index of fixed-size entries found by where a tile sits in the
quadtree rather than by a name, each entry compressed on its own so a
tile can be read without touching the rest. A name apiece would have been
seventy megabytes of index to read before the first tile could be drawn.
An entry carries what its tile's ground asks for - how far it departs
from the finest mesh, and how long its triangles are - because which
level to draw has to be settled for tiles that are not on the card yet,
and the index is the only thing about them that is read up front. Until
now the figure came from the tile's level, which is the worst tile in it,
so one steep corner spoke for every tile that shared its level.
The mesh carries a normal per vertex, octahedron-encoded into two bytes,
in place of the face normal the fragment stage worked out from how the
view position changed across a triangle. A face normal makes the ground
read as facets, and a coarser level's facets face differently from the
ones they stand for, so the light over a hillside changed as the level
did. A geometry stage hands the fragment stage the three materials of the
triangle it is in and the barycentric weights, so ground changes over a
triangle rather than along its edge; 3.3 has no gl_BaryCoordEXT.
And the level a tile is drawn at now counts the camera's height. The
distance was measured on the ground plane alone, which puts the tile
underfoot nought metres away from a camera a kilometre above it - and
nought metres asks for the finest level there is, so a view from the air
wanted the whole ground at full detail, more tiles than the buffers hold,
and what would not fit came out as holes.
Archives written under the old rules are refused at the door and baked
again.
The ground in a scenery is already an irregular mesh, so the cook keeps it: it cuts the
triangles along the tile grid, welds what coincides, and builds each coarser level by
collapsing edges. Nothing is resampled, nothing is interpolated, and a hole the scenery left
stays a hole. What was here before threw the triangles away, kept their vertices and built a
fresh Delaunay triangulation over them, which filled every hole, merged the two heights of
every retaining wall into one, and - because it never erased the super-triangle - emitted
indices three too large together with triangles reaching out to the artificial corners.
Tiles form a quadtree, as Cesium Quantized Mesh intends. A distant tile is a large one, so the
horizon costs tens of tiles rather than the thousands a fixed grid needed, and the level to
draw follows from the tile's own geometric error against what the screen can resolve - which is
what the format carries that field for. Every vertex on a tile's border survives into all of
its coarser levels, and so does every edge between two of them, so two neighbours drawn at
different levels share their border exactly: there is nothing to stitch and nothing to morph.
The file layout is the format's, with two deliberate departures, both written down in
quantizedmeshformat.h: the geodetic header fields carry scenery metres, there being no
geographic reference to convert from, and the material a vertex belongs to rides in an
extension of ours. Texture coordinates are not stored at all - ground tiles in world space, so
the coordinate follows from the position and from how many metres one repeat of the material
covers, measured off the scenery once and kept in the terrain's table.
Tiles live in one archive beside the scenery, an entry each, compressed on its own. Baltyk
cooks to 546 kB against 2.2 MB of heightfields, quark to 361 kB against 9.6 MB, tomaszewo to
375 kB against 9.9 MB.
Drawing is one call a frame: every resident tile lives in the same vertex and index buffer,
with its vertices measured from the middle of the terrain so that the whole map fits in floats,
and a frame is one glMultiDrawElementsBaseVertex over the tiles the walk chose and the frustum
kept. On baltyk that settles at 291 tiles resident, 16 MB of mesh, 85 tiles and 6k triangles
drawn.
What counts as ground is what the scenery says, not what its triangles look like. A node under
origin, rotate or scale is an object standing on the ground; a material with an alpha channel is
a tree, a bush, a fence or a catenary mast. Everything else is laid whichever way it faces, so
the side of an embankment or a cutting goes in with the rest instead of leaving a hole along
every bank. Whatever is left out is recorded per node, and the scenery goes on drawing it.
A cook is a cache: it is used again only when the archive, the note of which nodes went into it
and the manifest of what the scenery was made from all agree. A manifest listing a file the
scenery names but does not have used to fail that test for ever, since an absent file never
matches - quark has such an include, and nothing beside it could ever be reused.
tools/terraincook cooks the same way outside the engine, and meshtest beside it checks what the
cook promises: a tile reads back as written, neighbouring tiles agree on their border to the
millimetre, a hole is not filled in, a wall is laid exactly once, and a material's tiling comes
out of the source. seamcheck.py goes: it tested the morphing constants of a heightfield nothing
reads any more.
Each resident tile had a height texture and a material texture of its own, uploaded with
glTexImage2D, and was drawn once per material it held with every other material's
fragments discarded, all of them whether in view or not. Thousands of draws a frame.
Now the tiles of a level live in one pair of texture arrays (terrain_tile_pool), a layer
per tile. A pool starts at sixteen layers and doubles when full, copying what it holds on
the gpu, so a level takes only the memory its tiles need; uploads go through a pixel
buffer orphaned for each tile. The ground textures of every material are gathered into
one sRGB array with mipmaps (terrain_ground) - drawn into it layer by layer by a small
shader once the engine has each texture ready, since the scenery's textures are
compressed and cannot be blitted - with a table of placeholder colours and measured
tiling beside it.
Each frame the tiles in range are tested against the frustum by bounding sphere and
gathered per level into a buffer texture of instance data, and each level is drawn in
one instanced call. The fragment shader reads the four samples around it, drops the cell
when any of them carries no ground - exactly the rule the bake already assumed - and
blends the ground textures of their materials by distance, so material boundaries
follow the samples smoothly instead of stepping along triangle edges.
State the copy pass changes is captured and put back, and the texture unit cache is
reset after raw binds, so the rest of the renderer finds things as it left them.
On baltyk: all 30 materials land in the array, 663 of the 1120 tiles in range are drawn
after culling, and a frame is at most six terrain draws. The residency line in the log
now says how many tiles in range were drawn.
Levels changed at fixed distances - 512 m, 1 km, 2 km and on - whatever the window, the
field of view or the zoom. Now a level is used out to the distance where one of its sample
spacings covers terraindetail pixels on screen, 3 by default, which follows from the
viewport height and the vertical field of view with the zoom applied; each level doubles
the spacing, so each doubles the distance. Zooming in or a taller window pushes detail
further, a coarser setting pulls it in. The finest range never drops below four tile
sides, which the morphing needs to close the seams.
Levels and morphing both follow the finest range the last scan used, so they always agree,
and a change of more than a percent - a zoom, a resize - triggers a rescan.
tools/terraincook/seamcheck.py now also tries finest ranges of 5.7 and 11.3 tiles, and
finds no gap in any of them.
terraindetail is in the ini and on a slider in the debug panel; the panel's level table
and the residency line in the log show the resulting ranges. On baltyk the current window
works out to 484 m, so the 512 m minimum applies and nothing changes by default; a
scenery setting terraindetail 1 got 1349 m, and the samples on the gpu went from 3 MB to
10 MB with it.
Tiles drawn at the same level met exactly, but a finer tile beside a coarser one has
samples on their shared edge that the coarser one skips, and the ground between them
could open up. This closes the gap the standard way (CDLOD): each vertex slides towards
the next coarser level as its distance nears the end of its level's range, so that by the
end of the band a tile is, vertex for vertex, the coarser tile beyond it. Levels also stop
popping when they change.
The mip chain is point sampled, so the next level's grid is this level's even samples. An
odd vertex slides onto its even neighbour and takes its height, and the grid, whose
diagonals all run the same way at every level, collapses exactly into the coarser
triangulation. No second texture and no neighbour information is needed; the morph is
computed per vertex from its distance to the camera, the same distance the level is
chosen by.
Two things the geometry demands, both settled by tools/terraincook/seamcheck.py, which
walks random camera positions over 128 m, 256 m and 12.8 km tiles and counts every edge
vertex where the finer side has not finished morphing or the coarser side has started:
- the band ends a rescan's worth of travel (a quarter tile) short of the level's range.
Levels are chosen where the camera stood at the last rescan, the morph follows it every
frame, and a band ending at the range itself left gaps at every level boundary;
- the band is a fifth of the range wide, and level ranges are counted in tiles (four for
the finest level) rather than fixed metres, which keeps the coarser tile's band clear of
any edge a finer tile reaches, whatever the tile size.
The script finds no gap with these values. In the game on baltyk, a low view differs from
the unmorphed shader only in a strip of distant ground at the horizon, and nearer than
the first band the picture is identical.
The cooker's comment claimed tile seams were identical at every level; that held only
for neighbours at the same level, and now says so.
Today's work on the binary scene format plan (binary-scene-format-plan.md), from the
first measurement to a terrain that bakes itself on first run and streams from a
thread. The step-by-step history is kept on backup/scene-streaming-format-presquash-0916.
Measuring first. -loadprofile times a scenery load by stage and by node kind and reports
node counts and resident memory. On l204 terrain is 95% of the bytes and 99.8% of the
nodes; on quarkmce2007 vehicles, not models, dominate what is left. The terrain turned
out to be a heightfield in all but name, a ribbon covering 12% of its bounding box.
The heightfield. scene/heightfieldformat.h is the .ehf layout: Morton-ordered tiles
of 128 samples with one shared edge sample, a point-sampled mip chain, zstd per tile,
a nodata sentinel, a material palette with a measured tiling per material, and a stamp
of the rules that decided what counted as terrain. scene/heightfieldreader.h reads it
for the tool, the renderer and the loader alike, and scene/terraincooker.h writes it,
shared by the terraincook tool and the engine so a first-run bake is the file the tool
would have made. The cooker rasterises every triangle where it is drawn (through
scene::place_in_world, the placement the region applies too), keeps an upper surface
laid within half a metre over another and the lower of two further apart, and then
asks each triangle whether the heightfield shows it: laid, reaching a sample, keeping
nearly all it claimed, and with the ground around it drawn at every level out to 2 km.
Baking on first run. simulation/terrainbake bakes <scenario>.ehf the first time a
scenery is opened, choosing the grid step from the first 200,000 vertices, and on later
loads leaves out the triangles its node table says the heightfield shows. Everything
else - trees, grass tufts, gantries, bridge decks - is drawn as written, so a bad bake
can at worst draw something twice, and the heightfield sits 2 cm under the triangles so
the original wins there. Nodes are keyed by file, line, include parameters and
placement; an edited file changes its keys and those nodes are drawn again. A bake under
older rules, or without its table, is thrown away and redone. A launcher copy named
$scenario shares the scenario's files. -nobaketerrain shows the triangles as written.
A scenery can still name hand-cooked fields, several at different steps.
Drawing and streaming. rendering/terrainclipmap draws resident tiles at the mip level
their distance earns, deriving the grid from gl_VertexID and texturing in world space
with the scenery's own materials. rendering/terraintileloader reads and decodes tiles on
a thread of its own; the renderer rescans what is in range only after moving a quarter
of a tile, asks for what is missing nearest first, uploads at most 32 tiles a frame,
drops arrivals the camera has moved past, and keeps drawing a tile at the level it has
until the right one arrives. The terrain has its own range, terrainrange in the ini and
a slider in the debug panel, 20 km by default and independent of basedrawrange; the far
plane of an ordinary view is pushed out to it. The debug panel shows the range, tiles in
view, on the gpu, wanted and queued, and how many sit at each level.
Events. The event queue moved out of the events into a binary heap with a deterministic
tie-break, and an event is handed its activator instead of storing it, so basic_event
is a definition and nothing else.
The logic container. scene/logicformat.h and scene/logiccontainer write a scenery's
events, their targets and sibling chains as flat, deterministic arrays with a schema
hash that refuses a mismatched build. simulation/logiccook cooks it from the loaded
state whenever it is missing, stale or unreadable, reads it straight back to check it,
and resolves each target to a position in the registry its event kind searches.
-cooklogic forces a cook, -verifylogic only checks. Nothing reads it at load yet.
Prefabs. scene/prefab describes a signal by the aspects it can show - lights, speeds,
animation channels, a sound - instead of pasting an .inc per variant, and expands an
instance to ordinary scenery text. Tried on a light signal and a shape signal.
Screenshots without a person present: -shot x,y,z[,yaw[,pitch]], -shotsettle, -shotstay.
A template defined in a module interface is instantiated in the importing
unit, where its body's types must be complete. A declaration reaching the
importer only through the interface's global module fragment is not
enough for MSVC: cParser::operator>> uses std::stringstream, and every
unit that parsed a float got an incomplete type.
526 headers across 161 units, derived from what each interface's template
bodies actually name.
Every module unit now includes the standard headers it uses. Declarations
reaching a unit only through an imported module's global module fragment
are reachable but not visible, so ADL misses the free operators older
libstdc++ declares beside a type - reproduced on ubuntu 24.04 (libstdc++
13), where gl/vao.cpp could not compare vector iterators.
Also drops a stale editor/editorSettings.hpp from the MSVC source list,
which broke the Windows configure step, silences the deliberate
include-in-purview warning in the glm wrapper, and removes GCC support:
clang or MSVC only.
- The warning signal is no longer going to be played for an obnoxiously long amount of time by AI drivers when driving vehicles with a manual warning signal switch, most notably EN57.
- A new `moveDepartureWarned` driving flag has been created to accomodate this behavior.
- Added the action time counter and the missing driving flags to the Vehicle AI section.
