Stream the scenery: a baked terrain heightfield, a logic container, and prefabs

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.

application/application.cpp

@@ -66,6 +66,8 @@ import eu07.simcore;
 import eu07.utilities.globals;
 import eu07.utilities.utilities;
 import eu07.simulation.simulation;
+import eu07.simulation.loadprofile;
+import eu07.application.shotrunner;
 import eu07.simulation.simulationsounds;
 import eu07.vehicle.train;
 import eu07.utilities.dictionary;
@@ -1171,6 +1173,9 @@ int eu07_application::init_settings(int Argc, char *Argv[])
 
 	// process command line arguments
 	auto scenerywasasked = false;
+	std::vector<shot_runner::shot> shots;
+	auto shotsettle = 3.0;
+	auto shotquit = true;
 	for (int i = 1; i < Argc; ++i)
 	{
 
@@ -1202,16 +1207,91 @@ int eu07_application::init_settings(int Argc, char *Argv[])
 		{
 			Global.editor_startup = true;
 		}
+		else if (token == "-terrain")
+		{
+			if (i + 1 < Argc)
+			{
+				// cooked heightfield produced by tools/terraincook; may be repeated
+				Global.terrain_heightfields.push_back(Argv[++i]);
+			}
+		}
+		else if (token == "-shot")
+		{
+			// unattended screenshot: "x,y,z[,yaw[,pitch]]", repeatable for a sequence
+			if (i + 1 < Argc)
+			{
+				shot_runner::shot shot;
+				if (shot_runner::parse(Argv[++i], shot))
+				{
+					shots.push_back(shot);
+				}
+				else
+				{
+					std::cout << "bad -shot viewpoint: " << Argv[i] << std::endl;
+					return -1;
+				}
+			}
+		}
+		else if (token == "-shotsettle")
+		{
+			// seconds to wait at each viewpoint before saving, so terrain tiles and
+			// models have time to stream in
+			if (i + 1 < Argc)
+			{
+				shotsettle = std::atof(Argv[++i]);
+			}
+		}
+		else if (token == "-shotstay")
+		{
+			// leave the simulation running once the sequence is done
+			shotquit = false;
+		}
+		else if (token == "-loadprofile")
+		{
+			// scenery load profiling: where the load time goes, what the scenery holds,
+			// what it costs in memory. writes to the log and to loadprofile.txt
+			loadprofile::enable(true);
+		}
+		else if (token == "-cooklogic")
+		{
+			// cook the scenery's LOGIC container once it has loaded, then read it back and
+			// check it against the events in memory
+			Global.cook_logic = true;
+		}
+		else if (token == "-nobaketerrain")
+		{
+			// load the scenery's terrain triangles as written, without baking or using a
+			// heightfield baked beside it. the way to see the original for comparison
+			Global.bake_terrain = false;
+		}
+		else if (token == "-verifylogic")
+		{
+			// read the LOGIC container that is already on disk and check it against the
+			// scenery, writing nothing
+			Global.verify_logic = true;
+		}
 		else
 		{
 			std::cout << "usage: " << std::string(Argv[0]) << " [-s sceneryfilepath]"
 			          << " [-v vehiclename]"
 			          << " [-editor]"
+			          << " [-terrain terrain.ehf]"
+			          << " [-shot x,y,z[,yaw[,pitch]]]"
+			          << " [-shotsettle seconds] [-shotstay]"
+			          << " [-loadprofile]"
+			          << " [-cooklogic]"
+			          << " [-verifylogic]"
+			          << " [-nobaketerrain]"
 			          << "  (every switch also takes a double dash: --editor)" << std::endl;
 			return -1;
 		}
 	}
 
+	if (false == shots.empty())
+	{
+		Shots.configure(shots, shotsettle, shotquit);
+	}
+
 	if (Global.editor_startup && false == scenerywasasked)
 	{
 		// the editor opens on empty ground unless a scenery was actually asked for. whatever the ini