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"Devlog: Curves"

Posted: 23 September, 2017

I’m in the process of packing up my life for the move back to Tampere, so this will be the last catch-up blog until I’m setup again. Meh.

Neutrino

I’ve done a fair bit more work on this, due to travel, downtime waiting for estate agents and the start of the new Semester at University. The “big” new item is the curve editor.

I want the enemies to have pretty varied attack patterns, and although a lot of this could be done with the judicious use of Sine, you can’t beat having a decent spline to hand.

There’re a few ways you can do this, but I’ve opted for chaining cubic Bézier curves together, as the maths is about my level.

Or, in code:

{% highlight c %}

glm::vec2 CalculateBezierPoint(const float t, const glm::vec2* p0, const glm::vec2* p1, const glm::vec2* p2, const glm::vec2* p3) { float fT = clamp(t, 0.0f, 1.0f); float u = 1 — fT; float tt = fTfT; float uu = uu; float uuu = uu * u; float ttt = tt * fT; glm::vec2 p = glm::vec2(uuu * *p0); p += 3 * uu * t * *p1; p += 3 * u * tt * *p2; p += ttt * *p3; return p; }

{% endhighlight %}

ImGui has been a lifesaver, again, as it took very little time to put together enough UI to load, save and edit curves. There’s no real limit to the number of curves I can chain together, but in practice, two or three is more than enough. It’s simple, but it works.

The other nice addition to Neutrino, as you can see above, is embedded .GIF output. Totally stole this idea from Philip Bak, but it makes perfect sense; in a world where you need to fire out screenshots on social media as often as possible, what could be better than pressing a button and getting an animated .GIF, resized for Twitter?

We both opted to use this single header lib from Charlie Tangora. 3 function calls and Bob’s your mother’s brother. Perfect.

Other stuff that’s been done:

• Simple timer based callbacks, so single entities don’t need to constantly poll their state, they can just ask to do something in the future.
• Start of a level sequencer… This is based off the camera position, and will be responsible for doing all the spawning and in-game events. I’ll probably do a ImGui editor for this and talk about it in a future post
• Roughly sketched out how enemy entities will work. I’m trying to do existence based processing using a table layout — I’m high on Data Oriented Design kool-aid — so I’ll talk about this in a future post, once I’ve worked out how I’m doing it.
• Ran the codebase through Valgrind and removed a bunch of silly little memory leaks. One problem with the stop/start nature of the way I work on this is that, sometimes, if I have to stop in the middle of something, I forget to go back and clean-up after myself. I’ve got into the habit of just checking periodically in-case I’ve done something stupid. Normally I have ;D

Anyway, I better get back to packing boxes ;D

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