Releases 0.12 and 0.13: sandbox city and explosions

Releases 0.12 and 0.13 both shipped on October 2. Release 0.12 turned the game’s sandbox into a seeded city of about 200 m with roads running out past its edge, and release 0.13 reworked explosions. We cut both down to keep the long tail manageable, so height, highways, the 300 m city, paved roads and respawn moved to a later release.

Engine

• The camera now collides with the world. It is a 0.4 m sphere swept through the physics world each frame, so it slides along walls and cannot pass through terrain at any speed, including a 400 m drop in one frame. A sweep costs 6.5 µs at p50. We built this early because it would be harder to add later.
• Blasts throw what they reach outward, where craters and broken structures had lacked outward momentum. The push now travels as a shock front at 500 m/s, so a 40 m charge ripples out over a quarter of a second. For a 12 m charge at energy 8, pieces one to two reaches out move at 5.9 m/s on average, up from 2.3 m/s.
• Charges set off together no longer fling debris into the sky. A replay of twenty 40 m charges had left about 11,000 pieces climbing past 1.6 km at 370 m/s. A blast now raises a body’s speed only up to its own.
• A big blast sends a warping shockwave outward at 300 m/s, a little under the speed of sound, and the picture bends along its outline. Blasts with a reach under 4 m make none. The effect scales with the size of the explosion. The tone-mapping pass that draws it takes 0.47 ms with no shell, about 0.7 ms with one on screen and 1.07 ms with four.

Game

• The sandbox city has towers at the core, offices falling to low ones outward, a ring of Romanesque blocks, half-timbered houses on the outer streets, two parks and 14 billboards. Its edge wanders. It holds 78,000 to 87,000 members on three seeds, under the body cap of 131,072. On the low tier in Low Power Mode (a macOS setting that lowers clock speeds), seed 7 measured 5.9 ms p50 and 8.3 ms p95 per frame.
• The Sandbox menu takes a size, 150 m or 200 m, a district mix such as mixed, downtown or old town, and a seed typed as a number or a word.
• Billboards break into panels. The printed ad tears like paper along the seams, and a printed face is twelve panels of about 1.2 m.
• LED boards are 4 rows of 14 square cabinets. A cabinet that falls away goes dark, and the ones still up glitch more as more are gone. The app carries 44 ads, and one board in three is LED.
• Fireballs are staged. A white-hot core is gone in about a second, billows swell and darken to near-black soot over half a second, small pops burst inside the cloud, and a big blast adds a dark column that rises for 5 to 10 s. The first version was too uniform. With the same number of puffs, the worst case (twenty 40 m charges, camera inside the cloud) costs 31.0 ms GPU p95 against 30.5 ms.
• The ground stays hot after a blast, with glowing cracks that cool over 10 to 30 s. Craters throw clods of what they were cut from, and blasts shake the view.
• Gas pumps explode when broken, as large dark fuel fireballs with low pressure. We wanted heat and little concussive force from them. One broken pump sets off its neighbor and brings down 12 of the canopy’s 14 pieces.
• A gas station has a canopy on six columns, two pump islands, a brick shop and a price sign, and the sandbox places two. Four roads run out past the city’s edge.

Tools

• LED boards had been stuck on their first frame, and water ripples had stood still since the dam. Both read a time value the renderer never set. Both move now.