add heightmap exporter

[Qix-]

This probably isn't the cleanest implementation of this but I figured for people who want a quick and dirty exporter, here it is.

Downloads a .bin file upon clicking on "Export Heightmap" with IEEE-754 packed floats in a binary format. The count is the square of the heightmap resolution (1024, 2048, etc.) and they're un-normalized (i.e. they will almost certainly be >1.0).

If you're using Unity, you can rename it to have an extension .f32 and drop this in a script somewhere in your project to load it as a texture.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
#if UNITY_EDITOR
using UnityEditor.AssetImporters;
#endif


namespace MegaMine {

#if UNITY_EDITOR
[ScriptedImporter(1, "f32")]
public class F32Loader : ScriptedImporter
{
    public override void OnImportAsset(AssetImportContext ctx)
    {
        // Load in the float 32 values from the file.
        // The file is just a packed list of f32 values in binary
        // format. There is no header information; the number of values
        // is always a square number.
        byte[] bytes = System.IO.File.ReadAllBytes(ctx.assetPath);
        int numFloats = bytes.Length / 4;   
        int numFloatsPerSide = (int)Mathf.Sqrt(numFloats);
        float[] values = new float[numFloats];
        for (int i = 0; i < numFloats; i++)
        {
            values[i] = System.BitConverter.ToSingle(bytes, i * 4);
        }

        // Find the min and max values
        float min = values[0];
        float max = values[0];
        for (int i = 1; i < numFloats; i++)
        {
            if (values[i] < min)
            {
                min = values[i];
            }
            if (values[i] > max)
            {
                max = values[i];
            }
        }

        // Normalize the values
        for (int i = 0; i < numFloats; i++)
        {
            values[i] = (values[i] - min) / (max - min);
        }

        // Create a new texture to store the values
        Texture2D tex = new Texture2D(numFloatsPerSide, numFloatsPerSide, TextureFormat.RFloat, false);
        tex.wrapMode = TextureWrapMode.Repeat;
        tex.filterMode = FilterMode.Point;
        tex.SetPixelData(values, 0);
        tex.Apply();

        // Add the texture to the asset database
        ctx.AddObjectToAsset("main", tex);
        ctx.SetMainObject(tex);
    }
}
#endif

}