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Assets/Pixel3D/Scripts/MeshGenerator.cs

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+using UnityEngine;
+using UnityEditor;
+
+[RequireComponent(typeof(MeshFilter))]
+[RequireComponent(typeof(MeshRenderer))]
+public class MeshGenerator : MonoBehaviour
+{
+	public Texture2D heightMap;
+	public Vector3 size = new Vector3(10, 3, 10);
+	public Vector2Int sampleCount = new Vector2Int(25, 25);
+	public LayerMask terrainLayer;
+	[HideInInspector] public MeshData meshData;
+	[HideInInspector] public Mesh mesh;
+	[HideInInspector] public RenderTexture colorTexture;
+
+	void OnEnable()
+	{
+		var colorCameraObject = new GameObject("Color Camera");
+		colorCameraObject.transform.parent = transform;
+		colorCameraObject.transform.localPosition = Vector3.zero;
+		var offset = new Vector3(0, size.y, 0);
+		var rotation = Quaternion.Euler(90, 0, 0);
+		colorCameraObject.transform.SetLocalPositionAndRotation(offset, rotation);
+
+		var colorCamera = colorCameraObject.AddComponent<Camera>();
+		colorCamera.orthographic = true;
+		colorCamera.orthographicSize = size.z / 2;
+		colorCamera.aspect = size.x / size.z;
+		colorCamera.nearClipPlane = 0;
+		colorCamera.clearFlags = CameraClearFlags.Nothing;
+		colorCamera.depthTextureMode = DepthTextureMode.None;
+		colorCamera.cullingMask = 1 << (int)Mathf.Log(terrainLayer.value, 2);
+		colorTexture = new RenderTexture(1024, 1024, 0, RenderTextureFormat.ARGB32);
+		colorCamera.targetTexture = colorTexture;
+	}
+
+	public void GenerateTerrainMesh()
+	{
+		// Check if the height map is null
+		if (heightMap == null)
+		{
+			Debug.LogError("Height map is null");
+			return;
+		}
+
+		// Initialize the mesh data
+		meshData = new MeshData(sampleCount.x, sampleCount.y);
+
+		// Loop through each vertex
+		var index = 0;
+		for (var y = 0; y < sampleCount.y; y++)
+		{
+			for (var x = 0; x < sampleCount.x; x++)
+			{
+				// Calculate the uv, vertex position
+				var uv = new Vector2(x, y) / (sampleCount - Vector2.one);
+				var vertex = (uv - Vector2.one / 2) * new Vector2(size.x, size.z);
+				var heightValue = GetTrueHeight(uv);
+
+				// Set the vertex position and uv
+				meshData.vertices[index] = new Vector3(vertex.x, heightValue, vertex.y);
+				meshData.uvs[index] = uv;
+
+				// Add triangles if not at the edge
+				if (x < sampleCount.x - 1 && y < sampleCount.y - 1)
+				{
+					meshData.AddTriangle(index, index + sampleCount.x + 1, index + sampleCount.x);
+					meshData.AddTriangle(index + sampleCount.x + 1, index, index + 1);
+				}
+
+				// Increment the index
+				index++;
+			}
+		}
+
+		// Create the mesh
+		mesh = meshData.CreateMesh();
+
+		var meshFilter = GetComponent<MeshFilter>();
+		if (meshFilter != null)
+			meshFilter.sharedMesh = mesh;
+		else
+			Debug.LogError("Mesh filter is null");
+
+		var meshCollider = GetComponent<MeshCollider>();
+		if (meshCollider != null)
+			meshCollider.sharedMesh = mesh;
+	}
+
+	// Get the height of the terrain at the given uv from the mesh
+	public float GetMeshHeight(Vector2 uv)
+	{
+		// Calculate the precise indices
+		float xIndexPrecise = uv.x * (sampleCount.x - 1);
+		float zIndexPrecise = uv.y * (sampleCount.y - 1);
+
+		// Calculate the indices of the vertices around the point
+		var xIndex = Mathf.FloorToInt(uv.x * (sampleCount.x - 1));
+		var zIndex = Mathf.FloorToInt(uv.y * (sampleCount.y - 1));
+
+		// Ensure indices are within the bounds of the mesh
+		xIndex = Mathf.Clamp(xIndex, 0, sampleCount.x - 2);
+		zIndex = Mathf.Clamp(zIndex, 0, sampleCount.y - 2);
+
+		// Get the four vertices of the square (assuming row major and clockwise order)
+		var v1 = meshData.vertices[zIndex * sampleCount.x + xIndex];
+		var v2 = meshData.vertices[zIndex * sampleCount.x + xIndex + 1];
+		var v3 = meshData.vertices[(zIndex + 1) * sampleCount.x + xIndex];
+		var v4 = meshData.vertices[(zIndex + 1) * sampleCount.x + xIndex + 1];
+
+		// Bilinear interpolation
+		var xRem = xIndexPrecise - xIndex;
+		var zRem = zIndexPrecise - zIndex;
+		var height1 = Mathf.Lerp(v1.y, v2.y, xRem);
+		var height2 = Mathf.Lerp(v3.y, v4.y, xRem);
+		return Mathf.Lerp(height1, height2, zRem);
+	}
+
+	// Get the true height of the terrain at the given uv from the height map
+	public float GetTrueHeight(Vector2 uv)
+	{
+		var x = Mathf.RoundToInt(uv.x * heightMap.width);
+		var y = Mathf.RoundToInt(uv.y * heightMap.height);
+		return heightMap.GetPixel(x, y).grayscale * size.y; ;
+	}
+
+	// Check if the mesh and mesh data are generated
+	public bool IsMeshGenerated()
+	{
+		return mesh != null && meshData != null;
+	}
+}
+
+// MeshData class which allows for easy mesh creation
+public class MeshData
+{
+	public Vector3[] vertices;
+	public int[] triangles;
+	public Vector2[] uvs;
+
+	int triangleIndex;
+
+	public MeshData(int meshWidth, int meshHeight)
+	{
+		vertices = new Vector3[meshWidth * meshHeight];
+		uvs = new Vector2[meshWidth * meshHeight];
+		triangles = new int[(meshWidth - 1) * (meshHeight - 1) * 6];
+	}
+
+	public void AddTriangle(int a, int b, int c)
+	{
+		triangles[triangleIndex] = a;
+		triangles[triangleIndex + 1] = c;
+		triangles[triangleIndex + 2] = b;
+		triangleIndex += 3;
+	}
+
+	public Mesh CreateMesh()
+	{
+		var mesh = new Mesh
+		{
+			vertices = vertices,
+			triangles = triangles,
+			uv = uvs
+		};
+		mesh.RecalculateNormals();
+		return mesh;
+	}
+}
+
+#if UNITY_EDITOR
+// Custom editor which adds a button to generate the terrain
+[CustomEditor(typeof(MeshGenerator))]
+public class MeshGeneratorEditor : Editor
+{
+	public override void OnInspectorGUI()
+	{
+		var script = (MeshGenerator)target;
+		DrawDefaultInspector();
+		GUILayout.Space(10);
+		if (GUILayout.Button("Generate Terrain"))
+			script.GenerateTerrainMesh();
+	}
+}
+#endif