Creative Barriers

Some weeks, it's hard to think of what to build next.

You catch up on email, start a new todo list, watch twenty-two vaguely relevant Youtube videos, fantasize about a total rewrite - and somehow you're still not inspired.

But, this week wasn't like that! I knew I needed a Barrier spell, and I just needed to build it.

The Concept

Continuing the theme of, err, being inspired by Magicka, I wanted summoning Earth + Shield to create an impassable barrier: ¹

Idea: a barrier spike thrusts upwards from the earth to ward off melee attackers and projectiles.
(Concept art? No problem, I can do concept art!)

Conceptually, this is pretty straightforward, right? Just make a bunch of atoms slide up from the earth and we're done!

Moving Atoms

But... in my homegrown game engine, to move atoms as a group, they have to be in a moving body - linked to the rigid body physics engine.

And as far as the physics engine is concerned, a body must be one of two types: ²

• Dynamic, like barrels and rockets - these are moved by the physics engine in response to collisions (and forces I apply).
• Kinematic, like bullets and characters - these are moved by my logic directly.

I figured dynamic bodies wouldn't work well for this because rock barriers shouldn't be moveable by any other objects, but maybe we just try it?

But kinematic bodies come with a big caveat: they will do whatever I tell them to do.

• Move through a wall? No problem.
• Push a barrel through a wall too, making it glitch out? Sure!
• Pin a player's character so they can't move? With pleasure!

So you're meant to use them very carefully: moving platforms in a level editor, or bullets that disappear when they hit things - that sort of thing.

Letting a player place a moving kinematic body pretty much wherever they want? In the presence of other (dynamic) physics objects?

That's asking for trouble.

Handling Dynamic Bodies

Luckily, I realized that in this game there are only two types of dynamic physics objects: ³

1. Physics objects that explode.
2. Physics objects that don't matter.

So, I figured out an easy fix: spikes make explosive things explode instantly.

And for things that don't matter, like corpse ragdolls, well, I just turn off collisions between spikes and those things.

Will I ever need a physics object that can't explode but still matters? Hopefully not!

Handling Characters

Characters, like players and enemies, are supposed to be blocked by the spike.

But since you can place a spike anywhere, you can also trap players and enemies inside spikes, so they try to stop that:

As a bonus, it makes characters unable to stand still on the edge of the spikes, which makes enemies less adept at jumping over them.

Destroying Spikes

One thing I got "for free" from my engine was that the spikes were destructible from the get-go:

Except, well, spike pieces are not meant to float in mid-air like that. ⁴

Some really tedious coding later, it worked a bit better:

It might be cool to have those other spike pieces dissolve into sand once the spell ends,⁵ but I haven't implemented that.

Spiking Spots

Spikes slide upwards as intended, but in some spots the sliding looks horrible:

A neater solution might be to grow the spike as it slides up, and stop sliding when it hits a ceiling. ⁶

Lastly, the logic for where to place the spike also needs a bit of work still - it finds the lowest point in front of you, but sometimes that's on a platform way below you. ⁷

Elemental Effects

As always, each element you mix into (or repeat in) your spell adds an effect:

But I'm still deciding what mixing more Earth elements into a spike spell should do:

• Create more spikes?
• Make the spike tougher or last longer? (like Magicka)
• Change the size of spikes?

(...all of the above?)

Spiky web build‎

Go summon some spiky barriers: press E, 3, then some more keys of your choice, then left click: