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Karst Caves and More

merricksdad's picture

As I mentioned last week, this week I'll be going over the basic tile layout I discussed before I went back to school full time. One ot the things I really enjoyed about Sword Coast Legends was the potential in the tilesets to be something amazing. Potential is about all it had though, and the dungeon builder never ended up having ease of use. A DM had to randomize the dungeon 100 times to get the layout they desired. But not all was lost...

Many Groups to Choose From

Sword Coast Legends' original underdark tileset was built of what could easily be converted into many 3x3 tiles. Their tile centers, edges, or corners could easily be converted to doors, or closed walls, pits or pillars, pools or no-walk platforms. The whole concept of their tileset was almost made for conversion to NWN. The only problem was getting at all the material to attempt that conversion. I did this, but eventually found that the majority of their shapes were created with bumpmaps. Even so, their poly count was a bit ridiculous for NWN use, and converted directly to NWN meshes was a bit clunky.

Instead, I went to work on pulling out basic walkpath layouts, and found that the original SCL Underdark had approximately 25 unique 3x3 tile groups. In addition, they had many unique 3x6, 6x6, and 9x9 rooms. While looking through the file structure, I found that the groups were named simply by their shapes. One was called psi, another H, another Z. Here's a basic rundown of what SCL tilesets had to offer:

  • "Straight" tunnels: 6
  • 90-degree turns: 3
  • 4-entrance connectors: 7
  • 3-entrance connectors: 3
  • dead-end rooms: 3*
  • halls ending in stairs: 2*
  • stand alone rooms: 1

*one or two rooms double as entrance or dead-end

For the most part, the straight tunnels also doubled as a room, as did the 90 degree turns. Because the room is 3x3, and those areas in NWN generally only need a single tile, and they completed the transition in 3 tiles, there was a lot of real estate to play with on the other 6 tiles. This left room for alcoves, side ramps, lakes, and other inaccessible areas which give flavor to the dungeon. In fact, on any such 3x3 group, at least 4 tiles are just eye candy.

Prefab Concept

Sword coast legends treated their groups as prefabs. There is a basic layout over which 3-7 versions of additional prefabs can be placed. Each room may have up to 4 of these prefab placement areas. Many of these prefab locations were what you would see in the corners, or the center, but somtimes it would define the depth of a hole, or if a hole was actually a pillar. If there was a bridge or hole, it might define the mushrooms or type of water in the pit. In NWN we use entire tiles for this purpose rather than having prefab overlays that span multiple tiles, because in NWN, doing so can cause shadow and pathing issues.

Instead of making a library of super-complex meshes to line a room (which I was going to originally do), I'm making a super-library of less complex meshes that will become placeables a builder can import by choice by picking from a list. I'll be publishing a shopping catalog in PDF format for this purpose. I'll release a very naked version of each tile that can sub for SCL prefabs so a builder can construct their own best fit for their world. I'll then try constructing an SCL-similar tile that goes in that location and create a group which includes it in the NWN toolset, for each prefab. That's not to say I'm simply duplicating SCL. No. Because I have my own ideas as well, and would like to release hundreds of options for each 3x3, but that takes time.

What's New

This week I spent time thinking about poly counts and visual complexity. I posted all these smooth meshes with complex textures which would serve as replacements for SCL content, since we can't have the bumpmaps. But then I got to thinking about how much NWN can process in static models. Old Time Radio had a demo he released of a map pulled from another game. It was extremely high poly with many textures. This got me thinking, why not try forcing NWN to render high poly statics and learn to make realistic cave assets instead of painting them on billboards. So I did! I got to work thinking about the geometry and math of drapery structures and came up with some very interesting medium polycount hangers and shelves. With this, I started making options for the mesh library with higher poly count and where shadows and shapes would be illuminated as if real, rather than forcing dark and light into places the builder might not want.

The image below compares some of the high poly replacements with their initial low poly counterparts. Since all these items in the mesh library are closed solids, and I built that script which deletes faces inside other solids, I can now make a moderate poly landscape combining both versions and then bake the whole into a single scene. Objects the player will walk directin past will get the higher poly treatment, while objects further and further from character view will get less detailed in both texture and poly count.

Automatic Walls

In my first posts, I'd mentioned that I built a script to take a 3x3 tile form and programatically create walls and a ceiling from the master. This script generally creates a mesh with 100x as many faces as the master, but fits perfectly with the master as a floor, is seamless with adjacent tiles, and makes a good medium-poly background for higher poly placeables. Below are before and after screenshots of a cross-shaped room.

The basic idea here is to create a max height ceiling for the set, but which allows room for the builder to lower the ceiling or add decor which makes the room smaller. The mesh is also complex enough that I can take selections and stretch them out, making the room wider, or more shelf like in sections, while also retaining the original walkmesh.

In the image, the script is shown working on tiles which are 100% flat, but this need not be the case. I've created walkmesh masters which include stairs, ramps, and coils, and the script recognizes my wants. The only thing I would change at this point is to smooth the walls and optimize the mesh in the script. Of course this has the problem of reducing the stretchiness of the existing mesh, meaning I'd have to manipulate it more while I'm building.

What More?

The title of this post is Karst Caves and More. I don't want to do just a black stone underdark, and I don't want to just do a gray karst cave. I've designed most of this so if you change the textures you get a very differnet feel, but depending on decor and placeables, that might not always be true. So to remedy this, I'm going to release this set at least three times with differnet builds. The first will be strictly karst caves, and I'll name it as such. It will be less an underdark setting and more of surface caves setting, made for your characters to explore the upper underdark within about 300 meters of the surface, including underground rivers, skylight sinkholes, and waterfalls coming into the cave from above. For now, I'm leaving the caves natural and free of architecture of any kind. At some point I would like to add cliff-dwelling cultures in carved out side chambers.

The second iteration will definitely have that deep underdark feel. Limestone formations will be replaced with igneous masses and more jagged stones. Crystals and mushrooms will replace many of the fancy speleothems. That's not to say you can't use placeable crystals or mushrooms in the karst caves. Far from it. Rocks will be gray or black, and have crystal pockets. Things that don't normally glow may do so. I'm not taking the mushroom content to the level of SCL's middledark, but I am going to have a higher variety, with many of the placeables modeled after SCL, DDO, and NWO. Some pools may include acids rather than fresh water. Architecture, if any, will be a mix of drow and dwarven craftwork. Contrary to SCL's underdark, I want this to be exceptionally dark as a base, with even the rock feeling like it takes light away. I want torches out, or magical means to light your way, with only the occasional glowing thing to attract your eyes while monsters sneak up behind you. Builders can change specific areas with light and placeables.

The third iteration will be modeled after the SCL lava caves in the deeper underdark. All pools will be replaced with lava. Waterfalls and streams will have the same change. Mushrooms and crystals will be replaced with jagged black rocks and veins of metals. All rounded rock will be fresh smooth lava. Architecture in these regions may vary from drow to dwarven, or even illithid. Most of these caves will be dimly lit, and I'll put together a set of environments you can add to your environment 2da file to better flesh out the lava caves.

That's all for now. Over the next week, if I don't have full employment (the forklift is broken), I'll be working on this, or my yard. Either way, I'm building a stone wall.

First Release: 
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Mondego's picture

I merrick, glad you returned, and as always, with incredible good concepts.

Im sure you will really go out with this.

Remember that always the underdark worlds, contains, both the dark elves, and dark dwarv kingdoms, with some sort of alliance.

Thanks and good luck.


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CaveGnome's picture

MD said: "including underground rivers, skylight sinkholes, and waterfalls coming into the cave from above".


Whot ! Did you say "Cenote" ? This is one of my favorite underground nature jewels. If we could make something approaching in NWN, that would be way beyond fantastic. Bravo Merricksdad !


For the curious, link to the wikipedia entry:


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TheOneBlackRider's picture

You keep on amazing me! As so often: I do feel, that I still don't know that much... Well, I just keep on learning (eg. from you approaches and explanations regarding your trains of thought). Thanks!

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