Alliances of Solypsus 9

Posted on by tjkopena

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The third event of our Solypsus 9 campaign was yesterday. Eight teams comprising sixteen players total competed in the doubles format, each player fielding 1000 points. The Legions of Discord joined the battle, working to carve out a beachhead on the planet from the Spoiler Horde already invading and the Forces of Order defending:

  • Forces of Order: White Scars, two contingents of Imperial Guard, Adepta Sororitas, Kingbreakers Space Marines, and some surprisingly friendly Orks
  • Legions of Discord: Four contingents of Chaos Daemons, Chaos Marines, and Dark Eldar
  • Spoiler Horde: Tyranids, Dark Eldar, and two contingents of Necrons

More photos are in the gallery. Full results and missions are on the event webpage. Core campaign mechanics are in the Solypsus 9 outline.

Chaos arrives, on the wings of plague!

Chaos arrives, on the wings of plague!

Solypsus 9

The last two months of fighting began with a Tyranid and Ork horde dropping on the forgotten Imperial outpost of Solypsus 9. The horde quickly overran the Hab Blocks, but Imperium armies successfully shored up the Mine, Lab, Comms Tower, and Starport. In subsequent fighting the Spoilers took the Laboratory but the displaced Order troops reestablished themselves at the Generator. No doubt delayed in The Warp, this month the Legions of Discord finally arrived, hungry for battle.

Battle

Fighting renewed focused around the Lab and Hab Blocks.

  • First Round: Dark Eldar and Necron Spoilers correctly anticipated the primary threat on the Laboratory, making a move against the center of the settlement just as Imperial Guard and Sororitas troops attacked from there. The Spoiler attack though was disrupted by Chaos Daemons and the remaining Necron and Tyranid defenders in the Lab overrun. Meanwhile, yet more Daemons also clawed out of The Warp into the heart of the Hab Blocks, overwhelming the defenders and terrorizing the populance.
  • Second Round: Chaos Daemons and Imperial Guard both moved on the Necrons and Tyranids regrouping on open ground, but the Order was soundly rebuffed even as the Spoilers were crushed. On the hunt for fresh victims to buff up their strength, Dark Eldar supported by Necrons also successfully raided the Hab Blocks.
  • Third Round: Fighting spilled out all over the settlement, with Daemons and Kingbreakers making attacks on open ground to scour fleeing troops. Dark Eldar were routed from the Hab Blocks in the closing moments by Chaos Marines working in tandem with other denizens of Commoragh to betray their kind.
Tyranid harry Sororitas forces.

Tyranid harry Sororitas forces.

Dark Eldar swoop in from the skies.

Dark Eldar swoop in from the skies.

Captain Angholan faces off against the wormlord.

Captain Angholan faces off against the wormlord.

Outcome

Discord handily won each of the three rounds, for a total of 114 points versus Order’s 76 and Spoilers’ 66. Spoilers were routed from all the installations, with Discord taking up control of the Hab Blocks while Order regained the Lab while retaining the Mine, Starport, Generator, and Comms Tower. With both Discord and Spoilers targeting the Hab for control in this session but Discord winning out, the latter gained 6 campaign points in its first appearance. By gaining the Lab order achieved its target and, combined with the other installations, earned 12 campaign points. That puts the current standings at:

  • Order: 5 + 5 + 12 = 22 campaign points; 123 + 179 + 76 = 378 victory points
  • Spoilers: 1 + 4 + 0 = 5 campaign points; 110 + 140 + 66 = 316 victory points
  • Discord: 6 campaign points; 114 victory points

It was very clear very early on that all of the games would be extremely pressed for time in the doubles format, so I left out some of the narrative campaign elements originally planned. They’ll just have to make an appearance in next month’s finale.

Final disposition of armies and territories after the third event.

Final disposition of armies and territories after the third event.

Kingbreakers

An Ork player did not have a partner, so I wound up playing two matches with him and then a third on my own after he left.

Round 1: The opening deployment setup split up each team, and already not having a ton of obvious synergy with the Ork Green Tide we basically wound up playing two separate games on opposite flanks of the table. Facing oncoming Chaos Marines, I managed to sacrifice a Rhino and some Marines to draw their beast pack into combat with my Terminators. Otherwise I was concerned that the beasts would literally just run around them, the Kingbreakers never being able to tag them before they could swoop around to my home objectives. Unfortunately though the Terminators all failed their 2+/3++ saves and were swept off the field en masse. That left nothing with a realistic chance of stopping the Juggernaut lord from sweeping through all of my rear infantry. The Orks meanwhile were largely contained by opposing Dark Eldar, and the whole thing went down to a loss.

Split deployment zone setup for round 1.

Split deployment zone setup for round 1.

Round 2: Next, the opposing Dark Eldar + Necron team did a good job on mutual target priority and support in this Maelstrom battle. They wound up fighting as a real combined force, first primarily whittling away the Kingbreakers and then shifting focus to the Orks, still operating largely as distinct armies. In the early going though we established control over most of the board and leapt ahead. At one point we drew the Commander tactical objective (1 VP per objective) and were easily able to claim a whopping 5 of 6 objectives that turn. Several other objectives cards were also easy pickings. After that though the Kingbreakers were spread all over and picked apart, while the Ork blob couldn’t effectively claim new tactical objectives. The Spoilers slowly clawed their way back from a substantial deficit and eventually won by a few points.

The mob swarms through the rocks.

The mob swarms through the rocks.

In the first two rounds we were a bit disadvantaged as it just wasn’t clear how my Marines could work well with the Ork mob. With over 100 Orks crammed into 1000 points, they simply filled an entire sector of the board. Mixing the armies together evenly or putting the mob forward would have limited the more mobile Kingbreakers from moving about or engaging in longer range shooting. Conversely, putting the mob on rear defense would have forced the Kingbreakers’ defensive units into an awkward role. So, we wound up essentially splitting the board into two flanks.

That would be fine as such a mass of Orks could hold down an entire side, but they were grouped up into a Green Tide formation, making the vast majority of the army a single unit. That made them near impossible to dislodge, but rendered that huge points percentage only able to hold a single objective. Combined with being on foot, the blob just wasn’t able to effectively hold down all the objectives on its side, particularly in the more dynamic Maelstrom mission. We spent as much time trying to figure out how to move the other units of Gretchin and so forth through our own troops to actually claim objectives as we did working out offensive tactics.

Overall then, we had an awkward mix. Kingbreakers could take objectives easily, but needed support from a longer lasting force. Orks were longer lasting, but couldn’t really move to support or take objectives themselves.

Necrons and Kingbreakers pile in.

Necrons and Kingbreakers pile in.

Round 3: The final round was an old school matchup of 2000 points of Kingbreakers versus Chaos Daemons. I gave myself little odds of winning on the primary objective of annihilation, so from the start I focused on the secondary objective of holding markers. In addition, given that every match had been pressed on time and the opposing Chaos army particularly slow-playing with all its spells, Warp Storms, and other trickery, I strongly assumed the game would make it at most to Turn 4. This was born out when we only made it through Turn 3 and my army had taken heavy losses but few units been broken, while also claiming two of the markers and Linebreaker as well as First Blood. That eked out a win and nothing substantial would have changed in a turn, but a full five or six turn game would have swung hard the other way as units were wiped and markers forfeited.

Key here was that I had exactly what I needed to quickly grab the three secondary objectives and start off having to be dislodged, rather than fighting my way in: A bunker to put on home base, tanks to roll onto the midfield, and Drop Pods to go after the opposing marker. In general Marines can also just take a fair bit of abuse before they crumple. Terminators did a good job tying up several incoming units long enough that they had no chance to slaughter my squishier rear units. Captain Angholan (Vulkan) , Master Sauvon (Harath Shen), and Squad Scolirus similarly hung tough to draw out combat with both a Greater Daemon and a Soulgrinder in order to claim the far objective. Meanwhile, the other units did their best to not die and to make what contributions they could, like Sternguard in a single volley taking down a Nurgle Beast skulking about on the far flanks, for First Blood.

Placement of the three secondary markers.

Placement of the three secondary markers.

Finale

Next month will be the conclusion of our Solypsus 9 campaign. We’ll be running a 1000 -> 1500 -> 1850 point escalation format, with each list having to contain the previous list, as the armies and alliances hurtle into the endgame for control of the planet. Don’t miss out!

In the second round.

In the second round.

Asteroids: Moving Objects

Posted on by tjkopena

Recently I’ve started mentoring a local high school student a bit on implementing a video game, and this is a technical note toward that.

How objects move in simple arcade and action games is usually fairly straightforward, nothing more at the core than basic trigonometry and physics.

Game Loop

Most action games are a kind of real-time simulation, the core of which is a loop that updates essentially the entire world, all the objects and environmental effects in it, each cycle. That cycle is usually driven directly or indirectly by the frame rate, how many times a second the video display can or should be updated. Modern action games generally target 30 or 60 frames per second (FPS).

The relationship between frames and updates can get complex, but here we’ll assume we simply want to draw frames as frequently as possible and will update the world each time. A key detail even in this simple setup though is that a variable amount of time may pass between each update: The program will execute at different speeds on different computers, may slowdown if many other programs are open, and so on. We therefore need to account for that time in the update, so that the game plays basically the same in different environments.

The core of a typical action game program is then a loop that looks something like:

  While playing
    Calculate elapsed time since last update
    Update each object in the world by the elapsed time
    Render the current world

Calculating the elapsed time is a simple task of polling the computer’s clock. At the start of the program, the variable is set to the current time. Each update cycle, that variable is subtracted from the current time to give the elapsed time. The variable is then set to the time for this update cycle.

Rendering the world can use a wide variety of techniques, e.g., looping over all the game objects and applying a polygon drawing technique as discussed last time.

This rest of this post addresses moving objects in the world update.

Straight Line Movement

Moving in a straight line is a simple matter of displacing an object, shifting its x and y position.

ship-move

In practice, game updates may happen at slightly different intervals each frame, so it’s not quite as simple as merely adding a fixed value each cycle. Instead, the object is given a velocity which is multiplied by the time interval since the last frame to calculate the object’s displacement over that period.

x' = x + xvel*time
y' = y + yvel*time

Here x and y are the current position of the object, xvel and yvel the two axis-components of its velocity, and x',y'is the updated position of the object.

To set the object moving in a given direction, we simply set xvel as the cosine of that angle times the speed we desire, and yvel as the sine times the speed.

xvel = cos(angle) * speed
yvel = sin(angle) * speed

As discussed previously, keep in mind that most computer trigonometry functions operate on radians rather than degrees, and because the y-axis points downward, counter to typical conventions in mathematics, 90 degrees actually points down-screen.

Inertia

For objects that don’t change direction, the above is all that’s needed. Others, like the player’s ship in Asteroids, need to change velocity, e.g., in response to player input. In most games the player doesn’t change direction immediately but instead has some inertia, slowly moving from one direction to the next rather than just jumping to a new direction immediately. This is yet another reason to base movement around velocities and simple physics rather than fixed displacements or other schemes. Many games will additionally model acceleration to easily incorporate concepts like the drag of moving on a surface eventually slowing an object to a halt, or gravity speeding an object down to the ground when it falls.

The precise implementation and numbers used are some of the key elements defining how a game feels to play, and entire tomes have been written about these primitive physics in classic games, e.g., for Sonic or Mario. In many games inertia is fairly subtle. In Asteroids though it’s an overt, characteristic feature. The player’s ship moves as though it’s in space, gliding along endlessly with no friction to stop it, simply rotating in place until thrust is applied to change course. A simple way to do this is to track which direction the ship is currently facing, and manipulate that whenever the player hits the keys to turn. The keys to thrust forward and backward then simply trigger computing a velocity for the current direction, which is added to the current velocity.

xvel' = xvel + cos(angle) * thrust
yvel' = yvel + sin(angle) * thrust

Where thrust is the acceleration to apply. This is effectively taking the current vector of the ship, the new vector the player wants to move in, and adding them together to produce an updated vector reflecting the thrust applied to the ship’s inertia.

ship-inertia

Regulate Velocity

To keep the gameplay sane we need to cap the ship’s speed at some amount. Unfortunately we can’t just check to see if either velocity component has gone beyond a bound, because then the ship’s movement will be fixed in just that axis and it will move very oddly. Instead, we need to check if its speed—the magnitude of the velocity vector—is too high, and adjust its velocity accordingly. We do the latter by normalizing it, identifying the fraction of its speed contributed by the velocity’s x and y components, and multiplying that by the maximum speed we want to produce new, reduced x and y components that together fall within the bounds.

len = xvel^2 + yvel^2         // Compute length of the vector squared;
if len > max^2 then           // If we're moving too fast;
  len = sqrt(len)             // Compute the length;
  xvel' = (xvel / len) * max  // Normalize the components and multiply
  yvel' = (yvel / len) * max  // by our target max speed.
end

Note that we compare against the square of the maximum speed because computing a square root, to get the actual length, is traditionally a time-consuming calculation, though for this example it doesn’t matter. We therefore only want to compute it if necessary, and compare instead against the square of the bound we want to impose, a computationally cheap calculation to make.

Screen Wrap-Around

Finally, a critical part of basic movement is how objects interact with the boundaries of the world, which are often simply the screen itself. That in and of itself is a major question: Is the game world bigger than a single screen? Related questions further define critical basic behavior: Does the object stop at a world edge? Bounce? Wrap around to the other side? Does it have different reactions at different edges? As one small example of the latter, my little arcade game Gold Leader gives the player more tactical options, makes the screen feel bigger, and gives gameplay an interesting twist by wrapping the player around the x-axis but bounding them along the y-axis, whereas most similar games stop them at the edge of both.

In Asteroids, objects wrap around both edges of the single-screen world. This is handled through a simple series of checks and shifts in position.

if x < 0 then
  x += screenwidth
else if x > screenwidth
  x -= screenwidth

if y < 0 then
  y += screenheight
else if y > screenheight
  y -= screenheight

Note the additions and substractions. It can be jarring to just set the ship to the opposite side once it crosses over an edge. Hardly ever will the ship land exactly on an edge within a frame, instead it will typically have moved several pixels beyond. Adding and subtracting the dimensions preserves that slight difference and helps ensure the movement is visibly smooth.

Implementation

All of the above has been implemented in this little demo. Click on the game below to give it focus or follow that link, and then drive the ship with the arrow keys.

You can view the source to see the elements above implemented.

Shift on Solypsus 9

Posted on by tjkopena

bannerYesterday our Solypsus 9 campaign continued. Tyranids settled down to munch on biomass, Orks brawled with anybody they could, and some Necrons decided to help out the Space Marines and Guard, while Chaos finally descended in force. Ten players made it through the snowy streets:

  • Forces of Order: Swords of Dorn+Legion of the Damned, fascist Guardsmen, White Scars, Space Marines, and Necrons
  • Spoiler Horde: The Flying Swarm, Ork Mob, Death Guard, Traitor Marines, Rotted Daemons

More photos are in the gallery. Full results and missions are on the event webpage. Core campaign mechanics are in the Solypsus 9 outline.

Chaos Marines ride to the assault on Solypsus 9!

Chaos Marines ride to the assault on Solypsus 9!

Mechanics

The core of the campaign is based around a map of the sole settlement on Solypsus 9. The alliances are working to control one of the major installations on the planet—the Laboratory, Hab Blocks, or Mine—as well as the supporting sites—the Starport, Generator, or Comms Tower. Each round the alliances simultaneously place secret orders on their active armies. Those orders are then revealed and the alliances alternate assigning a player and a target to a chosen order, with the other alliance(s) responding with a defending player. Cumulative mission results then determine the outcome and control of each territory. Full details are in the draft writeup. The system continues to seem to be working really well, especially as more players get a better handle on it.

commands

map

Drop on Solypsus 9

In last month’s fighting, a massive Tyranid horde descended on Solypsus 9 with new Orkoid hybrid morphs. Caught off guard, the Imperium was forced to drop assault their own planet to shore up defenses as fast as possible. Lead by the Swords of Dorn, they successfully established positions in the Laboratory, Mine, Comms Tower, and Starport. The invaders though occupied the Hab Blocks and began feasting.

Battle

This stage of the campaign started off focused on the mine, and then swung onto the Laboratory.

  • Round 1: The Tyranid settled down in the Hab Blocks to gorge on biomass after their long journey through the stars, while the Orks mob continued to roll throughout the settlement in their jalopy battlewagons. Finally awoken to the major conflict on Solypsus 9, Chaos Daemons and traitors descended from orbit against the Imperial forces. Death Guard and their cultists attacked the Astra Militarum guarding the Mine and won the tactical battle but were rebuffed by supporting forces. Traitor Marines dropped on the undefended Generator and were surprised but not deterred to find Necrons phasing onto Solypsus 9. Rotted daemons meanwhile were intercepted by a collection of Space Marines. Swords of Dorn engaged the Ork Mob at the center of the colony but could not overcome their sheer mass. Finally sated, a Tyranid Harridan led a sortie of flying beasts that cut through the White Scars defenders and entered the Laboratory complex.
  • Round 2: The Swords of Dorn rushed to retake the Laboratory, crushing a Chaos beast pack on the way. Orks, Death Guard, and Tyranid made a combined assault on the Mine, with Space Marines, Imperial Guard, and White Scars defenders suffering a major defeat. Necrons meanwhile successfully took the central pathway of the settlement from the rotted daemons.
  • Round 3: Death Guard could not repel an onslaught on the Generator from the Swords of Dorn. Traitor Marines again assaulted the Laboratory and almost lost to White Scars defenders, but the Ork Mob arrived hot on the heels of Necrons moving on the facility and rolled over the entire complex. Daemons guarding the Mine were dispelled by the exhortations of Astra Militarum Priests and Psykers even as their Space Marines outriders were mulched by the Tyranid swarm.
Swords of Dorn advance through the slum shacks surrounding the Hab Blocks.

Swords of Dorn advance through the slum shacks surrounding the Hab Blocks.

Orks and White Scars engage in a frenzy of speed and close combat.

Orks and White Scars engage in a frenzy of speed and close combat.

Imperial Guard roustabouts take up arms under the banner of psykers and priests.

Imperial Guard roustabouts take up arms under the banner of psykers and priests.

Outcome

Although the individual rounds were closely fought, Order took the day with 179 victory points to 140 largely due to successfully claiming a number of covert missions in the second round. Spoilers advanced their position slightly, maintaining control of the Hab Blocks and gaining the Laboratory. Order meanwhile entrenched their position on each of the other installations. Neither side though claimed their chosen primary objective for the day, leaving Order slightly ahead on campaign points earned, 5 to 4.

Again, more photos are in the gallery, and full results on the event webpage.

Final campaign positioning at the end of the second event.

Final campaign positioning at the end of the second event.

Design Notes

One of the challenges in the campaign structure is that we don’t have a fixed group size or composition. The underlying mechanics seem to support this well, but some narrative sleight-of-hand is required. In this case, a bunch of last month’s Spoilers couldn’t make it but some new Chaos players did. The number of players though came just short of warranting a third faction. Absent that, I erred toward simplicity and narrative continuity and kept the factions as Order and Spoilers.

The highly modified and fairly original Maelstrom mission seemed to work well. I did though notice a preference to use the standard cards to draw and track objective numbers, rather than marking our sheet, then consulting our sheet to read the actual text in play. That’s not a really problem, but clearly people prefer the physicality of cards over checkboxes. There are logistical hassles though to rolling our own cards that I’m not sure how to work around, and I can’t see just switching to using the standard deck (more on that its many flaws in a later post).

A rotted Plague Drone roams the battlefield.

A rotted Plague Drone roams the battlefield.

On a similar logistical note, almost every table played the last round decidedly slow. I would guess some part of it was the extra complexity of the Maelstrom bookkeeping, though everybody I polled seemed to think it was mostly just being tired. In general I continue to think 1850 points is just a touch high for 2.5 hours for a group mostly on the more casual end of the spectrum.

For this event I started introducing a few narrative aspects to the actual gameplay itself. One of the rounds included Apparations, little entities scattering around scaring everybody. I forgot though one of my cardinal rules of game design for 40k: If a narrative mechanic doesn’t clearly benefit somebody or directly determine the game outcome, most people will forget or purposefully ignore it. I do exactly the same thing with Mysterious Objectives, for example. To avoid unbalancing games I gave people the option to simply ignore this—Patrick, with his low-leadership Orks, in particular looked terrified. Several did, but the rest mostly forgot about them anyway. Reinforcing that design lemma though, people continue to be pretty excited about the covert missions giving to the trailing alliance. So, for next month the narrative aspects will be reworked into the covert missions, which will also provide some more inspiration and direction for the latter.

Stormtroopers search the burning crash site of their downed flyer for fellow survivors.

Stormtroopers search the burning crash site of their downed flyer for fellow survivors.

Onward!

Next month is going to be a doubles format, players competing in teams of two with each fielding 1000 points. Doubles are by far the best attended 40k events at Redcap’s, and attendance has been a bit higher for our events recently than the previous trend, so I’m hopeful for really good turnout. Should be a blast!

The Swords of Dorn stand firm at the center of Order's campaign to defend Solypsus 9.

The Swords of Dorn stand firm at the center of Order’s campaign to defend Solypsus 9.