Creating Sprites Programmatically in Unity

So, I’ve been working on a game idea (yeah, I know, I haven’t actually completed any games thus far… my bad!), and have created some place-holder graphics for testing a few game mechanics. In other words, the visuals are not a permanent sort of thing. However, one of the mechanics will require some programmatically generated sprites to come into being as directed by a UI window the player will be presented with.

The basic setup is like this: The main game visuals are using Unity’s Tileset feature. The grid has (currently) three overlaid tilemaps: ground, ground shadows, ground clutter; the clutter being grass and flowers and other non-interactable bits for visual effect. Each tilemap moves up one in the z-sort order and all but the ground layer are using alpha transparency.

The programmatic sprites will be one z-sort layer above those (and below the player/NPCs) and is displayed at a target transform called CircleTarget. The initial code looked like this:

if (tex == null)
{
     tex = new Texture2D(256, 256);
     tex.alphaIsTransparency = true;

     Color c = Color.red;
     
     for (int x = 120; x <= 130; x++)
          for (int y = 120; y <= 130; y++)
               tex.SetPixel(x, y, c);

      s = Sprite.Create(tex, new Rect(0, 0, 256, 256), new Vector2(0.5f, 0.5f), 32f);

      CircleTarget.GetComponent<SpriteRenderer>().sprite = s;
}

This was intended just to put a small red square down where the CircleTarget lives, but instead I was just presented with this:

Ah, you need to apply changes – but also need to set things up for transparency. So, let’s try this:

if (tex == null)
{
      tex = new Texture2D(256, 256);
      tex.alphaIsTransparency = true;

      Color c = Color.red;
      Color a = new Color(1f, 1f, 1f, 0f);

      for (int x = 0; x < tex.width; x++)
            for (int y = 0; y < tex.height; y++)
                 tex.SetPixel(x, y, a);

       tex.Apply();

       for (int x = 120; x <= 130; x++)
           for (int y = 120; y <= 130; y++)
               tex.SetPixel(x, y, c);

       tex.Apply();

       s = Sprite.Create(tex, new Rect(0, 0, 256, 256), new Vector2(0.5f, 0.5f), 32f);

       CircleTarget.GetComponent<SpriteRenderer>().sprite = s;
}

Ah, much better, however the red pixels are surrounded by a buffer of whiteish/alphaish pixels. Of course, if you have existing sprites that you’re importing into Unity that use alpha and you want pixels to look precise, we need to change how they’re filtered. For programmatic sprites, you need to do the same thing.

tex = new Texture2D(256, 256);
tex.alphaIsTransparency = true;
tex.filterMode = FilterMode.Point;  // Add this line

...

And now we have a properly transparent background red square placed at our target location.

I’m a big fan of programmatic generation of meshes, sprites, and really everything. It makes the overall footprint of the game smaller and often consumes no more memory or processing power than what you’d have anyway – not always, but often. In this case, the programmatic option is actually significantly better than having a bunch of predesigned objects as sizes can be calculated on the fly and the variations that I plan for won’t require any palette-swapping, or even any palettes at all since it’ll just be stored in code. Generation of pixel art on the fly really opens up how this game mechanic can be used. I’m sure there will be more posts on it down the road – keep an eye out.

Palettes

I’ve started working on some color palettes for a few projects. Because we aren’t limited to 8-bit visuals these days, I’ve taken an atypical tack. Rather than having a palette for a specific biome or environment, I’m working on creating a variety of 8-color palettes that can be combined as needed in any various environment. The benefit here is that the total colors in a scene are still being limited, and the palettes can be used to ensure a visual “feel”, but more total colors can be utilized in a pixel art format.

Sulfur Pools
Seafoam
Hot & Cold
Greyscale
Flames
Cool Blue

I have ideas for about a dozen more and plan to utilize each of them in various ways. I also have CSS stylesheets made for them. I’ll upload those at some point and add links for anyone who might be interested.

Biome beginnings…

I’ve been wanting to make a system for a 2D game that would offer varying biomes. The two pieces I started on were creating noise-based shaders for each type of block/square, and working on deforming the individual quads so that they weren’t perfectly square, but did always match up along seams.

The beginning of this video briefly shows the near-infinite world space variance for the four shaders that I’ve got working so far. Clockwise from the top left, the materials are: iron, copper, coal, and gold. The movement is actually the whole tileset being moved around the world space (the camera auto-follows the center of the tileset). The second part of the video shows the deformed quads – which actually brings me to the “right” and “wrong” way to devise triangles for a mesh.

Pedants would say this is very much the “wrong” way to do so – that near-square shapes should be developed by pairs of triangles in any case where it’s possible. And for mapping textures to quads, that is certainly true, however the use case here is different.

First, there are no textures being utilizes. With it being strictly shader-based, and with the shader specifying values based on world positions, the triangle design doesn’t matter at all for the visual effects. Additionally, the methods I’m using allows for easy programmatic deformation with a virtually unlimited number of points along each side of the quad to be used for the deformation. Currently that’s being controlled by specifying the number of line segments each side should be broken down into.

Before and after deformation with two segments per side

This image is just breaking the quad’s sides into two segments each.

Before and after deformation with five segments per side

Here’s five segments per side.

Before and after deformation with ten segments per side

And lastly ten segments per side.

You can see that with five and ten segments, the actual deformation in the upper left is not manifold in two dimensions. But because the visual is being driven by shaders, it doesn’t actually cause any issues, and the tiles to the left and above this tile still line up properly meaning there’s also no z-fighting. While I still need to clean up the noise used for the deformations a bit, there’s a benefit to knowing that even errant geometry isn’t going to cause issues (because in a randomly generated world with tens of thousands of tiles, there’s always the chance for float-based math to be off).

The additional benefit to using “non-standard” triangles radiating out from the center is that it makes programmatic variation much easier to accomplish as no tile needs to know anything about any of it’s neighbors to deform and still fit properly. This actually leads into another useful factor noted below. But here, the math and calculations are just much easier. In the list of vertices, vertices[0] is also point (0, 0) of the quad – the center. All other vertices radiate outward, starting from the upper-lefthand corner and moving clockwise around the quad. This also means that setting the mesh triangle[] array is easier because every triplet starts with 0, and then stutter counts upward, e.g. – (0, 1, 2, 0, 2, 3, 0, 3, 4, 0, 4, 5, 0, 5, 6, …)

With such a simple set, a basic for-loop allows this to be done without prior knowledge of how many segments each quad has.

As mentioned above, there’s another useful bit here. If you look more closely at one of the before and after images, you’ll notice that the quad is centered on the world grid, which is not necessarily the default in Unity. Typically, a quad at coordinates (0, 0) would have it’s upper-lefthand corner at (0, 0) and it’s opposite corner at either (0, 1) or (0, -1) depending on how you have things set up. Here, when building the quad programmatically, rather than using the typical range of (0, 1) I use the range (-0.5, 0.5).

There are two primary reasons for this. From an object control perspective, this means that the tile at (5, -6) is centered at (5, -6), so destruction of that tile is the destruction of a 1×1 area centered at that position; there’s no need to worry about which direction the quad expands from it’s origin because the origin is the center. The second reason is from a programmatic geometry view. Because all tiles are centered, deforming the geometry along each x- and y- value between tiles is consistent between negative and positive worldspace.

Let’s take a little tutorial approach here to see what the code looks like. Here’s the creation of the quad itself. Yes, there’s some housekeeping to do with this yet, but it’s functional and fast.

        void CreateQuad()
	{
		Mesh mesh = new Mesh();
		mesh.name = "ScriptedMesh";

		Vector3[] vertices = new Vector3[1 + (4 * (stepsXY.Length - 1))];

		//Center
		vertices[0] = new Vector3(0f, 0f, 0f);

		for (int i = 0; i < stepsXY.Length - 1; i++)
		{
			//Top
			vertices[(0 * (stepsXY.Length - 1)) + i + 1] = new Vector3(stepsXY[i], stepsXY[stepsXY.Length - 1], 0f);
			//Right
			vertices[(1 * (stepsXY.Length - 1)) + i + 1] = new Vector3(stepsXY[stepsXY.Length - 1], stepsXY[stepsXY.Length - 1 - i], 0f);
			//Bottom
			vertices[(2 * (stepsXY.Length - 1)) + i + 1] = new Vector3(stepsXY[stepsXY.Length - 1 - i], stepsXY[0], 0f);
			//Left
			vertices[(3 * (stepsXY.Length - 1)) + i + 1] = new Vector3(stepsXY[0], stepsXY[i], 0f);
		}

		Vector3[] normals = new Vector3[vertices.Length];

		for (int i = 0; i < normals.Length; i++)
			normals[i] = Vector3.forward;

		int[] triangles = new int[4 * (stepsXY.Length - 1) * 3];

		int innerIndex = 0;
		for (int i = 0; i < 4 * (stepsXY.Length - 1); i++)
		{
			triangles[innerIndex++] = 0;
			triangles[innerIndex++] = i + 1;
			triangles[innerIndex++] = i + 2;
		}

		triangles[innerIndex - 1] = 1;

		mesh.vertices = vertices;
		mesh.normals = normals;
		mesh.triangles = triangles;

		mesh.RecalculateBounds();

		GameObject quad = new GameObject("Block");
		quad.transform.position = position;
		quad.transform.parent = this.parent.transform;

		MeshFilter meshFilter = (MeshFilter)quad.AddComponent(typeof(MeshFilter));
		meshFilter.mesh = mesh;

		MeshRenderer meshRenderer = (MeshRenderer)quad.AddComponent(typeof(MeshRenderer));
		meshRenderer.material = this.bMat.Material;

		this.self = quad;
	}

We create the mesh, and then determine the number of vertices. Again, because we aren’t turning a quad into a bunch of squares, this is an easy calculation, and there are no vertices aside from the center vertex that needs to be added.

Vector3[] vertices = new Vector3[1 + (4 * (stepsXY.Length - 1))];

Here, the number of vertices is 1 for the center, plus 4 * (stepsXY.Length - 1) where stepsXY is the number of vertices along each side. We’re subtracting 1 from each side because the second corner vertex of a given side will be the first vertex for the other side. In other words, if we’re breaking each side into two segments, you’d have {(-0.5, 0.5), (0, 0.5), (0.5, 0.5)} for the top, and {(0.5, 0.5), (0.5, 0), (0.5, -0.5)} for the right side. We don’t want or need to have (0.5, 0.5) listed twice in the array of vertices, so the -1 prevents that from happening.

We then add the center vertex to the array, and run through a for-loop that also only needs to execute stepsXY.Length - 1 times, as each loop hits the same point on all four sides. Yes, I used 0 * … in the first (top) calculations – this is just for clarity. You’ll also notice that in the right and bottom calculations, we’re subtracting i rather than adding it. This is so that triangles calculation later continues to be easier and all vertices in the array exist in clockwise order starting at vertices[1].

All normals are forward-facing, so it’s easy to just fill the normals array with Vector3.Forward given as many places as you have vertices.

Now the triangles array is initialized (remember to multiply it by 3 since each triangle has three vertices). Using an index/iteration value that is external to the for-loop allows for quick calculation; remember from above that the whole array is sets of 0, x, y where x and y stutter-step upwards. Finally, we set the very last triangle point back to 1 – the first value in the vertex array that is on the outer edge (this completes the circuit around the quad).

The rest is just building the mesh out. You may have noticed that I don’t build an array of UVs, nor plug UVs into the mesh building. Again, because I’m not using textures, there’s no mapping from a texture to the mesh, and therefore UVs are not needed. The shader doesn’t care about UVs. Of course, you could build shaders that DO care about UV calculations, in which case UVs would also need to be added (which may be a bit more complicated given the triangle geometry here).

Now we’ll look at the deformation code.

        public void DeformQuad()
	{
		MeshFilter mf = this.self.GetComponent<MeshFilter>();
		Mesh m = mf.mesh;
		Vector3[] vertices = m.vertices;

		for (int i = 0; i < vertices.Length; i++)
		{
			if ((vertices[i].x == stepsXY[0] || vertices[i].x == stepsXY[stepsXY.Length - 1]) && (vertices[i].y == stepsXY[0] || vertices[i].y == stepsXY[stepsXY.Length - 1]))
				continue;

			// Top
			if (vertices[i].y == stepsXY[stepsXY.Length - 1])
			{
				float noiseValue = Map(Mathf.PerlinNoise(this.position.x + vertices[i].x, this.position.y + stepsXY[stepsXY.Length - 1]), 0f, 1f, -0.3f, 0.3f);
				vertices[i] = new Vector3(vertices[i].x + noiseValue, vertices[i].y + noiseValue, 0f);
			}

			// Bottom
			if (vertices[i].y == stepsXY[0])
			{
				float noiseValue = Map(Mathf.PerlinNoise(this.position.x + vertices[i].x, this.position.y + stepsXY[0]), 0f, 1f, -0.3f, 0.3f);
				vertices[i] = new Vector3(vertices[i].x + noiseValue, vertices[i].y + noiseValue, 0f);
			}

			// Left
			if (vertices[i].x == stepsXY[stepsXY.Length - 1])
			{
				float noiseValue = Map(Mathf.PerlinNoise(this.position.x + stepsXY[stepsXY.Length - 1], this.position.y + vertices[i].y), 0f, 1f, -0.3f, 0.3f);
				vertices[i] = new Vector3(vertices[i].x + noiseValue, vertices[i].y + noiseValue, 0f);
			}

			// Right
			if (vertices[i].x == stepsXY[0])
			{
				float noiseValue = Map(Mathf.PerlinNoise(this.position.x + stepsXY[0], this.position.y + vertices[i].y), 0f, 1f, -0.3f, 0.3f);
				vertices[i] = new Vector3(vertices[i].x + noiseValue, vertices[i].y + noiseValue, 0f);
			}
		}

		m.vertices = vertices;
		m.RecalculateBounds();
	}

Currently, I’m just using Unity’s built-in Perlin Noise methods in the Mathf library. This leaves much to be desired, but before I dove into creating a noise function, I wanted to ensure this all worked as I expected. Basically, this just extracts the vertices from the mesh, performs the calculations on them, and rebuilds the mesh. The first if-statement is intended to keep the corners of each quad from becoming out of alignment. It probably won’t be kept, but it was something I was trying out.

You can also see that I map the noise function’s return values from (0, 1) to (-0.3, 0.3) as I don’t want any deformed vertex landing at or close to the center of another tile. I need to play around with this value some still, but it will depend on the noise function I end up with later on.

From a performance stance, it might be better to deform the vertices as the mesh is being created initially rather than creating a perfectly square mesh then proceeding to deform it. But this is the type of optimization that will almost certainly hinder legibility of the code, and keeping the two functions separate allows for more easily making changes to either function. And really, the amount of time taken is pretty small. Even with large sets of tiles, it takes no more than ~40μs to generate and ~27μs to deform each quad, for about 17s for over 250,000 tiles. The obvious plan would eventually be to chunk them (ala Minecraft), and there’s almost definitely some room for fine-tuning the process. Plus, this is just executing it in the editor, so it would almost certainly perform better in a release executable.

Working with NASA images to create Unity terrain

I’ve been wanting to create a scene in Unity based on real Martian terrain and recently chose Victoria Crater as my target. I’ve taken two NASA images, a false color image and a black and white image as my starting point. These two images below:

Victoria Crater, Mars
Source: https://mars.nasa.gov/resources/5633/victoria-crater-at-meridiani-planum/
Victoria Crater
Victoria Crater, Mars

The B+W image is an ideal starting point for a greyscale heightmap, but it has some critical flaws. Since a heightmap uses the greyscale level for determining height on a body, the shadows in the upper left make that section of the crater significantly deeper, the lighter areas on the bottom right roughly the same height as the surrounding plane, and the white shining bits along the edge significantly higher than anything else. That makes for a very poor topographical map.

So, cutting sections into various layers allowed for some gross manipulation of the overall scaling of colors using histograms. The first heightmap looks like this:

Victoria Crater Heightmap WIP
Victoria Crater Heightmap WIP

This is a more accurate representation by far, though still not as good as it could be. The feathered texture on the lower right quadrant of the crater doesn’t appear in the rest of the crater, despite very definitely being there in the source images. There’s also a bit of noise around the rim that really should be resolved, though it was worth importing into Unity as a trial. The result is:

Screenshot: Victoria Crater, Unity terrain from Heightmap
Screenshot: Victoria Crater, Unity terrain from Heightmap

I’m pretty happy with it for an initial attempt. It’ll need some fleshing out on the heightmap side. GIMP is a great tool, but it’s no Photoshop and some of the finer features in PS would definitely make this easier. That said, it’s almost certainly a workable option. Maybe a future project will be training an ML brain to take astronomic images and creating topographic heightmaps from them. I’d need better sources to start with, though. For now, I’ll need another few rounds of handmade maps.

Generative Glyphs

I came across this post on the Reddit sub r/Generative the other day and thought that u/ivanfleon had done something both relatively simple and also very cool. I had some ideas for generative glyphs and started by mimicking his sample there, thus was born the RectGlyph:

RectGlyph_01RectGlyph_02
Two different RectGlyph settings

The interface came shortly after RectGlyph was done as I was trying to troubleshoot work on the PolarGlyph. It made it easier to see what sort of variations could be had, but also allowed debugging to be more visual (which really helps me a lot).

I’ve always been fascinated with languages, both real and imagined. As I was working toward my PolarGlyph idea, I stumbled upon a few happy accidents, such as the RunicGlyph.

RunicGlyph_01RunicGlyph_02
Two RunicGlyph settings

And also the AngularGlyph:

AngularGlyph_01AngularGlyph_02
Two AngularGlyph settings

And eventually worked out the kinks for the PolarGlyph:

PolarGlyph_02PolarGlyph_01
Two PolarGlyph settings

I have a few others bring worked on, as well as some ideas regarding an editor so you can take your randomly generated glyphs and add line segments to or remove them from any of the glyphs in the set.

My pie-in-the-sky idea is to also be able to save them as a TrueType font so that they can be used in Unity (or anywhere), and possibly to save them as an SVG or vector sheet for use in various vector-based software.

It’s been a fun side project so far.

What to do, what to do…?

Still playing with some new Unity 2020 features, still dabbling on Labyrintheer as well as a few other projects. Learning a bit of Machine Learning just for fun, figuring out the ins and outs of HDRP and RT, and generally using this lovely COVID pandemic as time to reset a bit and figure out what I actually want to develop sooner rather than later.

For whatever it may be worth to you, if you are interested in Machine Learning, either specific to Unity, or more generally, I cannot recommend Penny deByl’s courses on Udemy highly enough. All of her courses are great, and the ML and AI courses are no different.

https://www.udemy.com/course/machine-learning-with-unity/

While the course is ostensibly about Unity and the development takes place within Unity, it isn’t specific to the Unity ML-Agents (though there are sections for that). The bulk of the course is geared toward developing your own agents and brains in C#, which is fantastic whether you want to use Unity’s ML-Agents or not.

In the immediate now, I’ve been working on some Unity code to create a system of CCTVs and monitors to show them. It’s a core component of a potential game idea I’m futzing with at the moment. I expect to have some pictures or videos in the next week or two to show off. Until then, Happy Thanksgiving 2020.

Playing with ray-tracing, Pt. 1

Back to working on Labyrintheer. But it’s Unity 2020, and I’ve been interested in playing with ray-tracing (RTX), so I started a new project, brought in some old assets and started toying with it.

The first entry is the trusty Gel Cube (from InfinityPBR) with RTX materials applied. This one is only lit by the internal point light that dies off when it dies. This is both of the attack animations and the death animation without scene lighting:

The next is with scene lighting. This is where RTX really shines with colored shadows cast through the transparent material of the GelCube:

The video quality isn’t as good as I’d hoped – need to work on that a bit.

Really, working with RTX in Unity’s HDRP isn’t terribly difficult, but there are a variety of gotchas that make it a bit of a headache, and materials are set up significantly differently (as are lights and scene volumes and…) That said, I plan to work on a few creatures first, just to get a feel for it all, then move on to bringing in the dungeons under RTX. Should be fun!

WIP: Wednesday Thursday

I’ve been working on a few items, the most recent of which has been lootable chests that have open and close animations and audio.  The animations and audio part are not something I have a lot of experience with, but the chest is thankfully fairly simple.

Right now I’ve defined a very specific Chest Controller, though I suspect I will transform this into a Usable Object Controller that will take an enum of it’s usability type (for environmental objects) like open/close, on/off, pick or gather (for reagents) and the like.  The video above is super simple, and is still a WIP.

Currently, the player will interact simultaneously with every interactable object within a radius.  The next step is to raycast or use a hidden collider to find the object most centered in front of the player and prevent interactions with objects behind the player.

It’s a start.

Work in Progress – 2017/10/17

A lot of core work on the project has been done over the past couple of weeks – and by core I mean behind the scenes.  Yeah, I say that a lot and rarely have something new to show, and this is one of those times.

However, as an independent developer, that’s how a lot of this process goes. I fixed the helium filled GelCube issue, and they seem to be functioning fairly well on their NavMesh.  Part of this was competing systems causing race conditions.  I toyed with the idea of using physics to drive them, disabling some of the Unity AI stuff, but that led me into a rabbit hole that I wasn’t in the mood to contend with.  Instead, I resolved the conflicts and they are now pathing along as they should.

I also added a physics material for them.  They’re made out of ice, and should slide around a bit more than other GelCubes and mobs in the game.  I’m also testing a fun bit where they may have items from their biome shoved inside them…  I mean, they’re likely to pick things up as they move about and grow, right?  I’m hoping this is a small detail that is cool in the long run.  We shall see.

I’ve started setting realistic masses for Rigidbodies as well.  The player has a mass of 81kg, and a full sized GelCube has a mass of 5444kg (who knew they were so heavy, but it does make sense).

Otherwise it’s been more boring: some maintenance to remove old assets that are no longer in play, some scripting for torches, creating static materials from SBSARs now that I have the walls and floors in a good place.  Oh, and modifying the Dungeon Architect DungeonRuntimeNavigation.cs file to support multiple meshes for multiple agents.  If you use DA and are interested, you can grab that here.

DungeonRuntimeNavigation Inspector
DungeonRuntimeNavigation Inspector

Basically you use an int[] to specify the NavAgentIDs that all your mobs will use and it builds all of their meshes and navigation data at the same time.  I know I’m not the only one who wondered for a while why I couldn’t use other NavMeshAgents in my Unity project.

How To See Your Player… Making Walls Transparent

Over the past several months working on the Dungeon theme for Labyrintheer, I’ve changed my camera angle several times.  I keep moving it higher to prevent walls and such from occluding the player, but I’m never happy with such an oblique view.  So, over the past few days I’ve been looking at options to make walls transparent when they are between the player and the camera.

Some solutions simply disable the geometry.  This isn’t acceptable for my game, and I suspect for many.  You could accidentally walk backwards out of the playable area, or an errant AI could take a bad turn during it’s pathing and fall off the world.  Plus, disabling geometry just doesn’t seem like an elegant solution.  My primary goal (and I’m still working on it) is to use a shader for this directly, though that seems like it has some major pitfalls (how do you tell a shader about an object other than the one that it’s drawing?).

So, for now I’m cheating with a very small amount of code and an extra material for objects that I want to hide.

Basically, I’ve duplicated the four wall materials I have, and the duplicate materials use transparency with an alpha value of 100.

My player controller script now calculates it’s distance from the camera every frame (though I think this might be able to be done once in Awake() since the distance should be fairly static), like this:

     void Update ()
     {
         GetInput();
         ProcessInput();
 
         distanceSquared = (transform.position - Camera.main.transform.position).sqrMagnitude;
     }
 
     public float Dist()
     {
         return distanceSquared
     }

Then created a script to go on the walls (or any object that needs to be transparent to prevent occlusion), as such:

TransMaterialSwap.cs

 using UnityEngine;
 
 public class TransMaterialSwap : MonoBehaviour {
 
     public Material _original;
     public Material _transparent;
     private GameObject player;
     private playerController pC;
     private Renderer rend;
 
     void Start()
     {
         player = GameObject.FindWithTag("Player");
         pC = player.GetComponent<playerController>();
         rend = this.GetComponent<Renderer>();
     }
 
     void Update()
     {
         if ((transform.position - Camera.main.transform.position).sqrMagnitude < pC.Dist())
         {
             rend.material = _transparent;
         }
         else
         {
             rend.material = _original;
         }
     }
 }

In the inspector I set both the original material and the transparent material.  If the object is between the camera and the player, it switches the object’s material to the transparent material.  It looks like this:

There are a few issues here.  First, I still need to profile this to see if the solution gives my runtime performance a hit.  I don’t suspect it’ll be TOO bad, but it doesn’t hurt to check, especially with larger maps.  I may look into options to only run the check if the object is visible to the camera rather than always checking on Update(), every frame for every wall.  The other issue is that by making it transparent, light comes through.  I’m not sure how big an issue this will be – it’ll require some play testing.  But it may be an issue in some situations.

Lastly, as I said, I really do want to attempt this in a shader.  I figure it’s a good method to learn shader programming, even if exactly what I want isn’t possible.