Well, I didn't want to do this whole thing over again, but I suppose I ought to.
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I'll now lay out how the lighting engine in Planet Coaster functions, which will become important in exploiting it.
So there's a lot of fuss about the new NVIDIA 'real time ray tracing' graphics cards. Why are these so cool? Well, typically a game will 'rasterize' your scene, meaning that all your lighting is fixed. Real time ray tracing allows you to bounce light rays all around the scene in realtime, creating a much more realistic scene.
In the case of Planet Coaster, light rays don't bounce. The light created by the light fixtures instead goes through this sequence:
1. Light flux leaves the object in the distribution set by said object.

Here's a simple diagram of what distribution is. A spotlight obviously looks much different than a sphere of light.
2. Flux travels through the scene until it strikes an object.
3. Light strikes the object. This leaves a faux light pattern on the object. The game says 'draw light here, and decay off'. This light is baked on to the object. It is simply the multiplying of a light map onto the color map of the object. If you've messed with the TMT this should make sense.
4. Object casts a shadow based on its angle compared to the light. This gets stored in the shadow map.
5. Light continues through the object, unencumbered by any previous objects it strikes. This becomes pretty important later. The game cannot occlude and stop light.
This sequence is pretty easy to observe in the game.

You see the light miraculously travel through walls to other walls behind it, while no light bounces onto the rear wall where it should go. In reality, light would continue to bounce back and forth between these two walls for as long as it could until the light fully decays to zero. Generally about 99% of the light is gone by the third bounce. In the game, there is no bounce light, and the light simply travels onward till it decays to zero. This is also set by the light distribution.
That creates some tricky things that you have to maneuver around in the game.
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So in today's lesson, I'm gonna look exclusively at what could be lumped as 'main street' lighting. For now, this encompasses the exterior elements of the facades and pathways. (I haven't done any interiors on my main street. If you have any files with interiors that you would like dissected and analyzed and modified, I'd be more than happy to take them!)
So I'll start by laying some ground rules for how main street lighting is supposed to 'feel' and what elements are important. Most of my references are from Disney because they happen to be the best examples by a longshot.
Keys to main street lighting:1. Lots and lots of light. Main streets are well.. the main street of your park. This means they are supposed to be lively, active, and inviting. Your lighting has to reflect this. That means pumping as much light as you can to highlight as much as you can. There's very little on the main streets that fade into the background. Your choices here are 'bright' and 'very bright' for the most part. There's not much subtlety to be had on a main street. It's a cacophony.
2. High visibility of people! This pairs with step 1 pretty well. The main street is also the most crowded area of your park, simply by nature, and so visibility is super super important. Guests need to be able to see the faces of others so they can avoid bumping into each other, but also so they can read facial expressions to some extent.
Think of all the times you've crossed paths with a stranger and you both weave to avoid each other.. but weave to the same side. Awkward. Seeing faces can help prevent that.
It's fairly easy to light up your facades sufficiently, but if your pathways don't get enough light, it's all out of whack and doesn't quite feel right. The main obstacle here is that in Planet Coaster, light doesn't bounce. So if you aim a light at a wall, it doesn't bounce back the other direction.
Here are two examples in Planet Coaster of good and bad visibility of people.

Here is a good example. You can see all the facial features of these people. There are no gross shadows across them. They feel 'normal'.

Now here is your 'Squidward' of park lighting.. In the dark. Undetectable. Doesn't match the light levels of the surrounding area. Just feels like someone put a black hole over the area and sucked out all the life. Even the daughter is unhappy about it. Don't be a Squidward.
I'll refer back to this later when looking at techniques.
3. Make people want the weenie. 'Weenie' of course being a term Walt used to describe a key point, such as a castle, that you want to draw guests to. In the daytime, you have to draw guests to your weenie with architecture and massing. At night you get many other tools. These may include:
1. Color. This is the easiest way to draw guests in. A blue color stands out against a red one.
2. Intensity. Stuff that's brighter attracts guests more readily than a dark corner.
3. Size. As with daytime, at night, the surface area of your weenie is still important. Lighting up a bigger weenie makes it far more appealing than a dinky little one (sorry fellas). Take note of this in your story. You may want a subtle weenie. You may want a garish gigantic castle. But the lighting will need to fall into place with that. Disneyland's castle and Walt Disney World's castle are very different. But the lighting doesn't try to turn one into the other. Cinderella's castle makes no attempts to be subtle and Sleeping Beauty's makes no attempt to be a spectacle, and that's ok. Think the story you want to tell.
4. Very congruent color temperature. Typically, your main street is nothing more than one giant show building on either side with a bunch of fake facades breaking that up with no space between the buildings. You have one vanishing point and it's one big cluttered scene. You don't have a lot of freedom to break up that vanishing point with color changes.
See Disney World here. Every building on the main street serves merely as a means to move the eye towards the castle. Any break up of this pattern would kill this movement and destroy the scene.

Now I'll make one small change, simply changing the color of the light affecting one small facade on the right, without making any alterations to the actual lighting design:

By just making this one building a little more blue, it suddenly competes with the castle. Due to the perspective of the street, it takes up almost the exact same field of view as the castle. This totally alters your story, as you've made this shop, in this case a crystal store, equally as important as the castle. Does this make sense? Certainly not in the case of Disney World, and probably not in your park either. Be mindful of this when you start to light your street.
These points of color are equally valid even when you aren't in a traditional environment. Say, you're in Tomorrowland. Lets take a look there instead:

While they've used tons of color, on any individual level, the color is fairly congruent.
-Green-
-Blue-
-Purple-
-Red-
With some splashes of yellow here and there. But you can clearly still detect the vanishing point and nothing competes in the scene. This is ideal.
4. Create points of focus beyond your weenie. So I had said earlier that tons of light is very important, and it is, another important thing to remember on main streets is that you still want to draw attention to all those shops with all the expensive merchandise you no doubt have stocking those shelves. Or the $20 margaritas and $10 appetizers.
So where do you highlight? The big ones are probably these three:
1. Entrances. Mainly doorways. These need to be brighter than the rest of the area. Guests will naturally flock to brighter areas. They are like a swarm of moths.
2. Window displays. This is where you show off the fancy merch. Again, people are like moths. See the Christmas Story for proof:

And all they had in there were some measly Raggedy Ann dolls and a model train!
3. Signage. This one is underrated but very critical. Nobody will go near your shop if they don't know what it even is. You do have to be a bit careful on signage, depending on your story. Too much and you clutter your scene into chaos. This may be your story, it may not be. But signage is the determining factor. See Nashville:


Now see Wisconsin. Pretty big difference. One is actually a place you want to spend time being in. The other is a depressing and cold wasteland. Unless you're building a Six Flags park, I can't imagine the second is your goal.
4. Stuff you will run into. This is a duh obvious one that can be forgotten, but if you have jutting out corners and steps that are in pitch black, you're gonna have a bad time. Kids with black eyes.. wheelchairs littering the pavement. Not great.
**photo redacted**
(When I add an interior section, there becomes many other critical areas, mainly your POS {point of sale, the registers usually} and the shelves. In restaurants it becomes a WHOLE other arena that requires a whole new set of criteria)
5. Uniformity of light. This is something I've touched on plenty in the earlier tutorials, but to reiterate it here I'll be concise.
Uniformity is good.. until it isn't. You want light that is congruent across your scene, but to completely eliminate contrast makes your scene a bore. I will touch more on this later in the tutorial.
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Ok, so now that I've laid out how lighting works in the game, I'll start digging into how I implement these qualitative criteria into (pseudo) reality.
First, I'll start with the general area lighting. This means the pathways that guests traverse, and does not include any vertical surfaces like the facades. Only the horizontal ones like pathways, and guests, which aren't really in either category.
I'll start with a true overview. How much light should you have? Well, I have about this much:

How does that compare to more standard areas of my park? Well, it differs by a ton. Here is another land in this same park from overhead.

As you can tell, the difference here is substantial. Why is that? Well, the main reason goes right back to point #1. Lots and lots of light.
It's simply an inevitability that to meet all the criteria I have set forth, you need to make your main street really really bright. No other lands besides your entrance street have such intense criteria.
Now, this is very hard to prove from aerials, but this photo shows something similar at Disneyland.

The main street is very clearly traceable from just the lighting. And is far higher in light levels than any of the surrounding areas. None of which can be as clearly seen from the air.

Contrast on the ground plane starts to become a serious issue even at this very simple level. I said that you want uniformity, but if you have tons of uniformity, you kill all your contrast. So how can you possible have both??
Well the answer starts and ends with one thing. Spacing.
Spacing is basically just how far apart you place lights. Closer spacing means more light and also more uniformity. Ideally you want to use as few lights as possible to achieve a uniformity that works. This would in the real world mean less money to spend on lights, as well as less clutter from poles all over the place, something that can really kill a screenshot.
Example:
/https://www.thestar.com/content/dam/thestar/yourtoronto/the_fixer/2014/06/18/need_a_light_theres_35_too_many_at_weston_rd_and_dennis_st/light_forest.jpg)
This intersection with about a million too many light poles. Don't do this.
Since you cannot increase the output of a fixture in the game, only decrease it, you have to get a little clever. Luckily it's pretty easy. I'll first detail how I've done it in this application, and then another application that is valid in less cramped areas.

If you look onto my main street, you'll see I have many many street poles all over. They are spaced fairly realistically in a way that doesn't clutter everything up.
This is how most lighting is accomplished in reality at theme parks. This is because lighting actually bounces around in real life. In Planet Coaster, light does not bounce. So you have to fake the impression of light bouncing through other methods.
Method 1: Hidden event lights
So what I discovered on a main street is that the street is almost always too wide to guarantee good shadowing for the peeps walking down the middle of the street, no matter how optimally you placed poles. How to stop this? Pretty easy. Just hide a bunch of event lights in your buildings.

Yep. That's it. Aim as many as you need towards the paths to make your peeps visible. One caveat is that this really can kill your game performance if you do it too much. So aim for thinner main streets and you'll have to use this less often.
Why does this work? Well, in reality, a main street is a very diffuse, very 'bouncy' environment where light is bouncing everywhere. This means less shadows. So these event lights do nothing more than emulate that bouncing of light around the scene that is otherwise vanishing. I use this type of exploit very very frequently in my lighting. It can replicate glow from windows, string lights, and on and on..
This is my preferred method. But you don't always have a place to hide a light that makes sense. If you are in an open pathway where there is no realistic way that light bouncing would happen, you have to somehow increase the intensity of your existing poles without killing your color.
That's also pretty easy, luckily.
Method 2: Poles only.

This is pretty easy. Just take your light and duplicate it and place it down in the same spot. This is one light.

Here's about 10 poles all in the same place. The more you place, the more filled out the sphere around the light becomes. Eventually you'd probably see a near perfect circle, but you end up with diminishing returns at a point, but it's great to help get that little extra brightness you need without changing the color of your light or finding some weird place to add another light. Just add one back in the same place.
This can become a performance drag that many probably want to avoid, but in most areas of the parks, you don't need to spam lights all that much. Usually one or two in one place will get the trick done. Main streets are again, just very rigorous to light and you need quite a bit of light.
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Method 3: Lights under the paths
Another common technique I hear people using a lot is burying lights in the pathways to light the guests. I'll describe here why that isn't always such a great technique.

Here I've placed a number of boxlights under the pathway. What you end up seeing is all the shadows are on the tops of the people, and not under their faces. They look creepy. This isn't the type of lighting you want. What you ideally want are shadows to come from overhead. This is what feels most natural.

Also, if you use the area light, you get this clearly visible pattern of light on the top of your path, totally blowing the illusion and giving away that you've just hid a bunch of lights under the path.

Aim for rows 1 and 2 of this diagram, avoid the bottom rows if you can.
Now of course, if you look back to how the lighting functions, there is no light bouncing off the ground, even though this would be happening in reality. So you COULD put a few lights under there to add in some more diffusion, but you have to be careful that your shadows on the people don't look really gross.
Method 4: Tall poles
Another fairly simple method is to hide big tall poles with the event light on them in planters and other nooks around your park. I don't generally love this method cause the poles usually are ugly and intrusive. But you can get away with them in certain areas where you aren't able to hide lights properly elsewhere.

Method 5: Lights in trees
This also has limited use, but can be helpful in a pinch. When your spacing isn't quite right for another street pole, and a big telephone pole is too intrusive, you may be able to get away with hiding some lights in the branches. Since the game doesn't block light, you can easily stash them without getting any light block from the tree itself.

Also visible in this picture is my technique for lighting up trees. Just recess lights a few feet from your trunk and point them up.

In this case they are angled back a bit into the main path. This prevents 'spillover' onto the adjacent building, which would have ruined my lighting on that facade.
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Facade Lighting:
Now onto the facades. My techniques here are generally pretty simple, but some can of course be performance intensive.
My two workhorses for facades are these:

They are low profile and have the most realistic lighting distributions. Also critically, you can change their color.

So here is my building. At a glance, you don't see any light sources. You see the area light poles, and a few wall sconces, yet all of the lights making the building 'glow' are hidden. In reality, the string lights on the building would be very bright bulbs that would illuminate most of the facades. There is so much light bouncing around on a main street that your buildings generally have lots of glow.

If I choose my lights, you can see I have a crapload of them hidden all over the place. This is madness for most parks and you could get away with far less, but this is my extreme example that gave me the light I needed.

To highlight the walls, boxlights are angled in. What is important here is that you don't put lights on your windows. From a realism standpoint, nobody is going to be shining lights into a room from the outside on purpose. The lights on the outside are meant to illuminate the walls, not the windows.
Above are some arm lights which illuminate the cornice. I managed to get them to blend in pretty well with the windows so that they don't appear to be lights. They just appear to be a part of the window frame.

I did similar spamming of armlights on the corner, where I wanted a bit more light. Back to earlier, remember that I said you have to draw focus to certain areas? Well corner buildings are certainly important, and adding brightness here makes them an anchor point in the scene.


Under the doorways, the classic boxlights are underneath. This is again overkill. Most parks you could get away with one or two. My main street is really bright, so to make much brighter areas than an already bright scene requires spamming tons and tons of lights.

Across the way, I've done similar techniques.

I tried my best to have the lights integrate with the architecture so that they feel fairly invisible. You can also see a stronger representation of what not illuminating the windows looks like.

A separate building here. Since the string lights in the game do not give off actual light, and are just bright texture, to realistically mimic the real lighting affects of them, you can also use armlights. This is an 'expensive' technique and why I generally avoid using too many string lights.

I have a little splash of color on my elephants, but not so much to overwhelm the scene.
Marquees and Overhangs:
Marquees may be another thing you have on your main street. They are simple to light and give you a nice shelf to place facade lighting.

On the underside I have many 'string' lights to represent the typical bulbs.

Recessed in the marquee are a series of area lights. This mimics the light from the bulbs.

You also get a nice shelf for the studio lights to illuminate your facade. They can create a very 'flat' looking facade, but also will save you a few lights.

For a more basic canopy, you don't need to have two full layers and can get away with either the boxlights or area lights, depending on your preference. In this case, I liked the boxlights better.
Sconces:

Sconces are of course a very very common light source. Were I designing a real street, I would use them extremely heavily. However, there are very very few decent sconces in the game. Most have no ability to change their color, thus rendering them almost useless.
Here are the few sconces I will use the most:

These ones have fairly inoffensive and traditional colors. The Munsters ones are a bit more blue, and the spooky ones a bit more yellow. The rest in the game are super super yellow and gross and I avoid them like the plague.
The other downside to these sconces is that they are just big blobs of light that can overwhelm the scene if you overuse them. For that reason, I tend to use the more controlled methods above on my facades.
Illuminated Windows:These can be quite useful, but only when the theme of the window matches the theme of your building. The only lit windows are from the spooky pack and are thus very rugged. They do retain the color and texture of the window which makes them useful.

You can get around this by recessing the illuminated color panels into your windows when you don't have the option of using an illuminated window. This becomes very tricky and tedious, and also forces you to plaster over the window texture, costing you some depth, especially during the day. The TV screens can work here too, but again, it just becomes really tricky and tedious to map it all correctly. Not really worth it unless you REALLY need a window to look illuminated.
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So what I'll do now is start the lighting of a structure from near start to finish.

Here is the building with no lighting. I opted for one illuminated window in the center tower.

Now, I place an armlight to illuminate the tower further and supplement the glow of the window. This makes it feel a little less painted on and illuminates some of the structure that would realistically be illuminated by the window glow.

Next, I added some more armlights onto the roof. They are made to mimic 'snow-guards' which prevent snow from falling several stories off of roofs and crushing people. My park is based in the northeast, so this is within my story.

Next I add in my sconces. They give some glow to the facade elements. I opted for these over the pricier armlight techniques as I managed to get these to work well, and I really didn't have anywhere better to hide more lights without aiming them directly onto windows.

And finally, I add the large area lights under my canopy. This makes the building inviting, and gives enough light on the pathway for guest visibility.
I could have added a few more layers to the upper structure, but for whatever reason, I stop here. I like how the light tapers off as you move up the structure. It gives it a sense of size.
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So that's all I have for now. I'm not sure when the next installment will come. If you have more ideas for things to add, please let me know and I'll try to touch on it.