Release 0.15: city depth

Release 0.15 adds depth to the cities: water, cars, trees, more building types and furnished interiors. The release closed on October 7 with what had been built, and the tight city keeps both of its street-front mixes. The second half of the release is performance work on large cities, driven by freezes we hit in play.

Game

• The larger parks have ponds. A pond’s water is a simulated grid, so a crater dug beside it drains it and the water runs in. A pond holds about 2.15 m of water at the middle. A blast pushes a cavity and a ring of waves through the water, and a car or ship that goes in splashes, sends out a ring and sinks.
• The first splashes looked like steam and chunks of paper, so splashes are now drawn as streaks of spray and whitewater.
• A broken hydrant jets water about 5 m up for 20 s, tapers, and stops at 32 s, and the water wets the ground around it. We wanted the hydrants to stop on their own.
• A community pool, a 25-yard tank of six lanes with a bathhouse, stands in every city. We made it a building type so a map holds at most two bodies of water.
• Trees stand in parks, along streets and in yards, 181 in seed 7’s mixed city.
• About 250 cars are left in each city’s streets, parked at curbs and in knots at crossings as if everyone had fled. About 14 rounds set one burning, and 3 to 7 s later its fuel goes up and sets the cars beside it burning. A car is crushed when something ten or more times heavier lands on it.
• Cities have two parking garages where there is room. Cars fill 12% of the stalls, down from 30%, after chain reactions overwhelmed the game in large maps.
• A hotel with a balcony for every room stands in each city. Cities of 250 m and up give part of their outskirts to warehouses and sheds.
• Heavy industry joined the stock in this order: a cooling tower 114 m tall, a tank farm that burns down tank by tank, and a chimney.
• Every furnishable building and every house has a door at ground level on its street face. Shops are furnished by trade, in eight kinds. A fifth of the offices stand vacant with leasing posters.
• Six suburban house types were built as scenes: ranch, Cape Cod, Colonial, split-level, Craftsman bungalow and a modern two-story.
• Close, Far and Nose camera positions join the chase view, with a field-of-view slider. We made tight handling the default after flying both.

Engine

• Stalls of 0.2 to 1.4 s after blasts in large cities came from several causes found by replaying our logged sessions. The worst simulation frame in one replay fell from 202 ms to 31.5 ms.
• The renderer now skips buildings outside the view for the depth and shadow passes. In our large cities the live shadow pass had taken 5.8 to 7.9 ms against 2.8 ms in a still benchmark.
• The Large sandbox city is 250 m, and the physics body cap doubled to 262,144 to hold it.
• Buildings differ by member and by age, with darker, grayer walls, grime and rain streaks. Dust settles on surfaces after a collapse. Walls take bounce light from the street in front of them, and the grade warms as the sun lowers.

Tools

• A gameplay recorder writes a movie with the HUD and an events file beside it. A tool cuts the newest recording into a reel of about 75 s, since a plain screen capture ran long and dull. The first reel was short on dogfights, so a kill now counts as much as a big blast.
• Pressing a marker key in play writes the 20 s of frames before it into the session log, to point to the moments of a freeze.