At the close of my earlier update I mentioned wanting to try 'Tracer-style' time travel where only the player moves backwards and everything else stays in place. I gave it a go and got it working, but it wasn't particularly interesting. It was basically just the player moving in the opposite direction. Animation could probably jazz that up, but a more fun idea came to me in the middle of a sleepless night:
Seeing the future.
Trivially, if everything in the world rewinds and the player can make different decisions, that's basically seeing the future. And that's what I built:
It's not perfect. You'll notice that the dynamic cubes retain their velocity after the time rewind happens, but that's solvable.
Here's how it works: there's a global time keeper which records the current tick. The base class has three methods (_process, get_state, and set_state), and two variables (start_tick and history).
The global time keeper sends a signal when time starts to rewind. During the rewind process, each tick is a step backwards instead of a step forward. The _process method of the base class checks to see if a rewind is active and, if so, calls set_state(history[global_tick]). If rewind is not active, we append or update the history. There's some nuance to tracking deltas and despawning, but really that's about it. Simple, eh?
And so the brain storming begins. I feel like anything that doesn't explicitly involve time-travel of some sort will get dinged by the Theme-Adherence police, and besides, time travel is fun.
I've never made a game with time travel before, but it presents plenty of opportunities to do novel things. At the very least, even if the mechanics aren't original, I can do things like make the player character switch from replay to AI-driven if the player interacts with his/her previous self or force players to avoid interacting with their previous selves by avoiding line-of-sight and such. All of this is predicated on Terminator-style time travel, where the player goes back into a previous timeframe and can never return to their original. Minute Physics calls this "new/changed history" time travel and I'd call it 'forked history' time travel. The other form would be self-influencing time travel, where you happen to see yourself from the future coming in to your present.
I tried a lot of architectures. It began with the simplest thing I thought would work: A controller component would record keypresses and emit signals. The parent object would listen for signals on the child component and act as though it were receiving input. This worked, but it was hard to jump to a specific point in time.
The next thing I tried was a 'global manager'. Each actor had a 'get state' and 'set state' method. In record mode, actors would append to their history. In replay mode, they'd pull from history and set state. Things got complicated when it came to handling travelling backwards in time and then interacting differently. It was easy to go back to a time and replay, but it wasn't easy to go back, replay, and record at the same time. That part was necessary if we wanted to see ourselves and interact in tandem.
The third thing I tried was similar to the first. Each actor would be a deterministic function of time. We 'set time' which consists of taking the time and setting state accordingly. Functions are determined as only a function of the current timestamp. That works fine. After playing with it, however, it's really hard to make puzzles for it.
I'm going to try the Tracer-style time travel thing where the player can go back 60-Seconds into their previous state while the world stays as it is. This is closer to the self-consistent/non-branching timeline.
Thematically, I really want to rip off Zero-Wing and do a terrible translation of the plot. Character has a time-travel device that sends him/her back 30 seconds, but it has a 60-second recharge. The player got a lethal dose of radiation and needs to go back to save him/herself. The goal is to get past unity and into the net-time-gain territory. Either a recharge of 29 seconds or a jump of 61 seconds.
I put together this halftone shader effect in Blender earlier today:
The key realization for me was that Blender's shader nodes allow you to use Diffuse BSDF or other shaders as inputs to your setup. This means we can take the lightness of our mesh and use that as an input to a color ramp with a step function in it. In more detail, here's the shader setup:
I'd wager a more skilled artist could replace the dot-pattern generator with something that gives more consistent result and doesn't have that semi-circular banding issue. Give it a try and let me know if it works out for you.
Cameras are hard. If you've ever found yourself fighting against a camera that would really like to pivot in a direction you don't want it to, you've been on the receiving side of this technical difficulty. The reason behind your struggle is simple: spiteful developers.
Not really. Or at least probably not. The fact of the matter is that making a camera which balances the atmosphere of a game, moves quickly enough to keep up with the player, moves slowly enough to not move around with the player's jitters, and accounts for the corner cases like a player getting teleported -- it's not a simple thing.
I'd like to talk about the different methods I've been experimenting with in Clearing Skies. This is as much a journal entry for me to see what I've tried and why it works or doesn't work as anything else. I hope that someone may find some insight in it.
Approach 0: Strap the camera to the player.
This is the simplest and most straightforward approach to moving the camera. Wherever the player moves, the camera follows.
Simple! Easy to implement and understand.
Basically no corner cases where movement will be odd.
There are some drawbacks, and they're not too hard to see. When the player shakes or moves about drastically (like if she shakes after a shock or hit), the camera is liable to jitter along with her. Shaking the camera is a good way to induce nausea or eye strain in the player. Additionally, you lose the sense of level depth. The entire space is continuous. This is fine, generally, but for the first dungeon in particular, this felt to me like it shrank the space considerably.
Can cause eyestrain for sudden movements.
No way to add 'cinematic' elements on transitions between rooms.
Maybe there's an easy solution to the rapid movement problem? Indeed, we can try...
Approach 1: Smoothed Camera Movement.
The camera smoothly transitions between where it is and where the player is located. This solves a lot of the issues with the player shaking rapidly. It's like attaching a spring to a camera gimbal.
Still easy to implement.
Reduces eye strain from rapid motion.
The downsides are visible in the gif above. The biggest issue we run in to is the rapid movement of the player between rooms. The camera has to spend a few frames catching up to the player location on transport to a distant location. This can be solved by snapping the camera (disabling smooth on transition), on setting a max threshold before the camera teleports, or a few other tricks. No matter what, it's a bit more involved than simply assigning a location, and it still doesn't give us the cinematic room sweeping we want.
Camera has to catch up on long moves.
No cinematic controls.
Approach 2: Camera Zones
When the player character enters an area, the camera's bounds are set to match the region. This means the camera moves smoothly inside the zone, sliding to follow the player and 'transitioning' when the player moves between regions. I like the way this looks -- it divides the map in such a way that it makes things appear larger than they are.
Looks good. Cinematic.
High degree of control over where the camera moves. Can cut off areas outside of the map to avoid wasting screen real estate.
It's not perfect, though. Transitions are very abrupt and might cause issues with visual tracking of the player. It's also very cumbersome to implement, as the zones need to be defined manually:
Furthermore, troubles come in the way of overlapping rectangles. Not the region on the bottom where it may be necessary for two zones to overlap. Plus, when we finally leave the map, the bounds for the camera will need to change. Lastly, when we change the camera bounds, we lose the ability to smoothly transition between states.
Possibility of weird edge cases when moving between zones.
Time consuming to put together regions.
Not clear how to restore full camera zone when leaving dungeon.
No smooth transitions.
Visual tracking is hard on screen switches.
In a more perfect world, I'd love to be able to define small pins which act as boundary keepers for the camera, then, if a distance is exceeded, have the camera quickly tween to the player location and return to tracking. I don't have a solution for that worked out yet, however. Time will tell if I get it solved.
Bucky Isotope recently made mention of building the US-Mexico border wall entirely out of LEGO, following it with an inquiry on how much such a wall would cost. Twitter, even with the newly increased comment size, still did not provide ample room for the calculation with sources. This short piece will serve that purpose.
We will assume that the wall will be comprised of 2x4 LEGO brand building blocks for the sake of simplicity. It is possible that a more cost effective wall be made if a different piece is chosen as the basis, but it will suffice for our purposes.
A 2x4 LEGO brand building block has dimensions 16mm by 32mm by 9.6mm.
If we simplify the surrounding border (heh) and remove the cap insets, shifting the volume instead to the perimeter by increasing the thickness to 1mm from 0.8mm, we can sum the four walls and 'ceiling' thusly:
Left: 15.8mm * 9.6mm * 1mm = 151.68mm^3 Right: Matches left. Front: (31.8mm - 2mm) * 9.6mm * 1mm = 286.08mm^3 // We subtract 2mm for the thickness of the left and right walls. Back: Matches front. Top: (31.8mm - 2mm) * (15.8mm - 2mm) * 1mm. = 411.24mm^3 // Subtracting for the front, back, and side walls.
Total volume: 849mm^3 = 0.849cm^3.
At the time of writing, LEGO blocks are manufactured from acrylonitrile butadiene styrene (ABS), having a density of 1.05g/cc. A 2x4 LEGO brand building block then weighs approximately 0.89145g, giving us 1121 blocks per kg.
We can convert an average eBay cost of approximately $50/lb to $110.23/kg, or approximately $0.0893 per block.
The US-Mexico border is 3,145km long from the Gulf of Mexico to the Pacific ocean. Assuming blocks were stacked using the long side, it would take approximately 98,900,000 blocks for a grand total of $8,831,770.
The wall would stretch an impressive 9.6mm into the air and would weigh 88.16 metric tons.
If a taller or wider wall is required for some reason, one can calculate this by multiplying for every additional ~10mm of height desired and again for every 16mm of width desired. For example, doubling our wall from 9.6mm to 19.2mm would double the cost to $17,663,540. Doubling the width to 31.6mm would double the cost again to $35,327,080.
The average adult male from Mexico is 172 cm. To construct a wall with this height at a thickness of 15.8mm would cost approximately $1,582,358,791. It would require a human to be moving at least several centimeters per hour to breach.