TaleSpire Dev Log 224

Hi everyone, last week was intense but productive. I’ve been down at Ree & Heckbo’s place, working on the engine. We had hoped to start integrating our branches, but my stuff still was not ready, so instead, we just kept working, making use of the collaboration advantages that being in the same room gives.

As there has been a bunch of stuff happening, I’m gonna spread it over a few posts.

Let’s start with something random: line-of-sight.

Line of sight checks came up in conversation in the community recently. The issue was that people have issues because one creature can block the line of sight to other creatures behind it. This is one of those things that sounds like it makes sense but just doesn’t feel right in-game. Any gaming using miniatures is always an approximation of the fantasy setting, and so sticking to it like it represented reality often doesn’t make sense.

Let’s take a concrete example. A giant is blocking the view to a goblin behind its leg. This sounds fine, but imagine the scene as it would play out in ‘real-life’. The giant would be towering above you, and as it walks, you catch glimpses of the goblin as it darts about trying to get a shot on your comrades. This fidelity is lost if we treat the table as ground truth.

Instead, it’s better to ignore iter-creature relationships when checking line-of-sight.

This poses a minor implementation issue that is worth exploring. Back in the alpha, we checked line-of-sight using collision rays. This worked, but it was inaccurate as you can only perform so many checks per frame. Back then, we checked less than 10 positions per creature, and both false positives and negatives were common. People rightly asked for a more accurate line of sight.

In response, we changed the approach to rendering the whole scene from the creature in question’s perspective. We rendered tiles and creatures into a cubemap using colors as IDs. We then used compute shaders to gather the results and report back what colors (and thus creatures) we visible. As you can see, this introduces the issue that any creature that is entirely obscured by another creature will be considered invisible.

To fix this limitation, we are going to need something new. The idea is to render the scene without creatures into the cubemap, then we will render all the creatures, but they will not write their depths (in-fact, we will probably discard all their fragments). This means that we should get a fragment shader call for every fragment in each creature that isn’t discarded by depth. We can then write the visibility info from the fragment shader into the result buffer, hopefully giving us the data we need.

This will also help fog-of-war, which uses the same visibility cubemap. (more on fog-of-war another day).

I’m gonna jump back into code now, more dev-logs coming when I take breaks!


Published: September 14 2020

  • category:
blog comments powered by Disqus