Unity Custom Attributes and Custom Editors

Shapes Editor 01
Custom editor/inspector view for Shapes.cs

While working on Programmatic Meshes, it became clear that I needed some custom gizmos to help me visualize things as I moved along. It really became a necessity as I was working on sphere generation because I was having some issues where certain sizes and segment counts were creating bad geometry. This was almost certainly due to ordering of the int[] array for triangles associated to the mesh. Since everything is generated by code, that means that once all vertices are created, the code needs to also sort/order those vertices the same every time to ensure that the facet tris are created correctly.

Sphere Vertices Indices
Sphere Vertices Indices

This was my first venture into gizmos aside from some very basic line drawings. I wanted the indices of each Vector3 in the mesh so that I could ensure they were getting properly ordered each time and would meet the requirements for tri calculation. So the above was born – and damn did it ever help me see where things were occasionally not working (sadly, I don’t have a screenshot of the bad sphere, but let’s just say that it was… not an ideal geometric shape).

After getting through that, I wanted to also change the inspector so that I could enable/disable vertex visualization. As shapes become more complex, the numbering is great, but I wanted a better visualization of the vertices in the scene view. As the screenshot above illustrates, unless you rotate the view around a bit, it’s easy to get lost with where vertices actually are in relation to one another.

Sphere Vertices Visualization
Sphere Vertices Visualization

In the above GIF, you can see how movement helps determine what indices you’re viewing, but the ROYGBIV and SIZE options for visualization also help. In the ROYGBIV mode, the closest vertices are red and the furthest are violet, and everything in between follows the ROYGBIV order. With the size option, the closest vertices are the largest and the furthest away are the smallest, and they are scaled to suit in between. In either case, they’ve updated in real time. I’m not yet sure how this performs on very high density meshes, and I’m sure some optimization will be necessary, but it’s good enough for my needs for now.

I wanted the collapsible Viewables area in the inspector for this, as well as for mesh data (Vertices[], Normals[], and Triangles[]). I also wanted to be able to select the Shape (each of which is a class inheriting from Primitive()), and which Generate() method should be used (each shape has different generate methods).

For this to work, I created a few custom classes, which I added to my external DLL:

SelectableList<T> is a custom List<> type collection that has an interactive indexer property called .Selected that references the index of the selected item in the list. This has turned out to be handy for selecting items in lists from dropdowns in the inspector.

MethodCaller<T> is a custom collection that contains a reference to a class (in this case, each shape class gets a method caller), and a SelectableList<MethodInfo> of the generation methods in that class.

And lastly, MethodDictionary<T> is a custom collection class that collects MethodCaller<T> objects. Its constructor takes a filter for classes (to remove the base class and secondary base classes where inheritance takes place on multiple levels), and a filter for methods based on the name of the methods to acquire.

The creation of the MethodDictionary also builds out the dictionary based on the filters provided, so there isn’t a lot of work needed to implement it. This is definitely a plus.

In the Unity code, I also created three custom attributes:

[Segmented] is tagged to generate methods that use the segment count value. This allows that slider to be enabled/disabled on constructor selection.

[DefaultGenerator] is tagged to generate methods that the default Generate() method passes to.

[GeneratorInfo] is tagged to all generate methods and provides inline help text in the inspector, typically what segment count actually accounts for if it’s used, and what the measure/size value indicates (e.g.: circle/diameter, quad/size, hexagon/apothem*2).

Using reflection, I do something like this in the ShapeEditor.cs script:

if (shape.shapeMethods.Callers.Selected. Methods.Selected. GetCustomAttributes().SingleOrDefault(s => s.GetType() == typeof(SegmentedAttribute)) != null)

It’s not terribly pretty, but it’s fairly quick – quick enough for inspector draws – and allows the inspector panel to change on the fly as selections are made.

It’s worth noting, if you haven’t worked with custom attributes before, that the attribute doesn’t need to have fields despite all examples I came across online containing them. Without fields, it’s basically a check to see if it exists or not – a boolean of sorts applied to a reflected method to change how the inspector is drawn. Some examples:

[AttributeUsage(AttributeTargets.Method)]
public class SegmentedAttribute : Attribute
{
}
[AttributeUsage(AttributeTargets.Method)]
public class DefaultGeneratorAttribute : Attribute
{
}
[AttributeUsage(AttributeTargets.Method)]
public class GeneratorInfoAttribute : Attribute
{
    public readonly string info;

    public GeneratorInfoAttribute(string info)
    {
        this.info = info;
    }
}

And usage on a class method:

[Segmented]
[DefaultGenerator]
[GeneratorInfo("Generates a circle based on the 'starburst' pattern.\n\nSize is the diameter of the circle.\n\nSegments is the number of segments _per quadrant_.")]
public Mesh GenerateStarburst() { /* code */ }

I will probably write some additional posts about this, maybe with more code, as this project continues. And I’m sure I’ll have a Part 2 of Programmatic Meshes in the next week or two.

Programmatic Meshes, pt. I

I’m not sure how many parts this will end up being, but I’ve been spending a good amount of time lately on programmatically generating both 2D and 3D meshes. Currently, I’m working on a library to expand the Unity primitives system to create meshes based on parameters. So far, I’ve built Quads (standard/two triangle, starburst array from center), Circles (starburst), Hexagons (starburst, compact), and Triangles (equilateral, right). I’m now working on basic spheres from sets of circles.

Single Circle
Single Circle
Sphere from circles
Sphere from circles

One thing that these shapes do, so long as the shape object is kept, is track vertices across changes. I’d like to do some basic deformation options down the road, but for now this works well because for the sphere, I create just a single circle, copy its vertex[] rotate it and copy over and over until it’s complete.

The above image, “Sphere from circles” is actually just multiple circle objects rotated properly. My current speedbump is sorting the vertices for the sphere itself. The vertex at (0, 0, 0) is removed, and the vertices where x=0 are only parsed from the first circle rotation. All vertices are then ordered descending by y, so from the top down. Now I need to also sort the x/z values in clockwise order so that the vertex[] basically stores the vertices as horizontal slices from top to bottom, then clockwise for each slice (or counter-clockwise). This is necessary so that the triangles can also be generated programmatically without intervention.

My current attempt was something like this:

this.vertices = vertList.OrderByDescending(o => o.y).ThenBy(o => Mathf.Atan2(o.x, o.z)).ToArray();

But that doesn’t properly sort the x/z components. I’m sure there’s an easy formula that I’m missing, so… I’ll have to keep working through it.

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.

Pixel Art Tutorials – Small House

So I’m playing around with pixel art – which was the reason I started messing around with palettes. I am not an artist, but I want to gain some pixel art skills. I figured I’d share my trials and tribulations on this journey because… why not?

I’ll be using some simple tutorials from some great artists, including: Slynyrd (who also has a great blog), Pedro Medeiros, and Rémy Devaux.

I plan to try limiting myself to an eight or fewer color palette (though that may not always be possible). When the tutorial isn’t behind a paywall (is otherwise freely available), I’ll share both the tutorial and my result. Bear with me as the first attempts will likely not be so great.

First tutorial is from Slynyrd’s 3/4 Top Down House.

And my first attempt…

Small House, animated pixel art
Small House, animated pixel art

Not great, but not awful. At least it’s obvious what it’s supposed to be, which is more than I can say for many of my attempts at art.

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.

HyperDisk Kickstarter

For anyone who has backed campaigns on Kickstarter, you probably know that they’re sometimes a crapshoot. Back in 2019, I backed two portable SSD projects: HyperDisk and WarpDrive. Both were expected to deliver in early 2020, but a combination of a suddenly volatile SSD market and the COVID pandemic caused them both to sort of evaporate – vaporware, if you will. Many started hammering both as scams, demanding refunds – a fairly reasonable response given that many campaigns go that route.

WarpDrive may very well have been a scam. The creators haven’t posted an update since January 2020. HyperDisk has had updates and, much to my surprise, I actually received mine today. So, of course, I set to benchmark it against their purported 1000MB/s claims.

HyperDisk CrystalMark
HyperDisk CrystalMark

It does actually meet those speeds using the supplied USB-C to USB-C cable to the Thunderbolt 3 port on my laptop. Internally, the enclosure is a 3.1 Gen 2 interface with an M.2 NVMe SSD. The cost during the campaign was US$139, and for a comparable (what appears to be a 2242 form-factor stick) SSD with an enclosure, it came out to be pretty much a wash in February 2021 prices, though for the time it was a pretty decent deal. I haven’t opened it up to look, but I’m presuming a 2242 based on the size. I’m also not sure the branding on the stick itself.

HyperDisk CrystalInfo
HyperDisk CrystalInfo

The part number, HYPCNV001T doesn’t bring up anything in Google.

We’ll see how it holds up over time, but for now I’m not terribly displeased. I’ve come to expect Kickstarter campaigns to deliver long after their estimates. I’ve backed 128 projects to date, though many have been just a $1 backing as a show of support (if a lot of folk gave even a dollar to many “good” projects, more would end up with the necessary funding – worth thinking on). Of the ones with a deliverable product that I’ve backed at a tier to get said product, ~80% of them have gone beyond their time tables, and of those, half or so by quite a ways… often a year or more.

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.