Implementing TerrainShape from Jitter in Jitter2

[mgpreston]

Hello,

In Jitter there was a TerrainShape that could be created from a heightmap. I'm trying to upgrade a codebase that uses Jitter to use Jitter2, and this type no longer exists. What's the analogue for this in Jitter2, if any?

Thanks!

[notgiven688]

Hi @mgpreston,

in Jitter2 you should use the TriangleShape for terrain. The workflow looks like this:

1. Create a List<JTriangle> which represents your terrain. If you need help converting {float[,] heights, float scaleX, float scaleZ} to this list I am glad to help. Pass the list to the constructor of TriangleMesh, see here: Demo05_L54
2. Create (Fat)TriangleShapes from the instance of TriangleMesh from step 1, compare Demo05_L56-59
3. Build a RigidBody by adding these shapes, see Demo05_L71-L74

[mgpreston]

That's very helpful, thank you!

I gave it a go based on the MakeHull method from TerrainShape in Jitter. Am I on the right track with this approach?

public static class Terrain
{
    [Pure]
    public static TriangleMesh CreateMesh(float[,] heights, float scaleX, float scaleZ)
    {
        var heightsLength0 = heights.GetLength(0);
        var heightsLength1 = heights.GetLength(1);

        var triangleList = new List<JTriangle>();

        for (var index = 0; index < (heightsLength0 - 1) * (heightsLength1 - 1); index++)
        {
            var quadIndexX = index % (heightsLength0 - 1);
            var quadIndexZ = index / (heightsLength0 - 1);

            triangleList.Add(new JTriangle(
                new JVector((0 + quadIndexX + 0) * scaleX, heights[0 + quadIndexX + 0, 0 + quadIndexZ + 0],
                    (0 + quadIndexZ + 0) * scaleZ),
                new JVector((0 + quadIndexX + 1) * scaleX, heights[0 + quadIndexX + 1, 0 + quadIndexZ + 0],
                    (0 + quadIndexZ + 0) * scaleZ),
                new JVector((0 + quadIndexX + 0) * scaleX, heights[0 + quadIndexX + 0, 0 + quadIndexZ + 1],
                    (0 + quadIndexZ + 1) * scaleZ)
            ));

            triangleList.Add(new JTriangle(
                new JVector((0 + quadIndexX + 1) * scaleX, heights[0 + quadIndexX + 1, 0 + quadIndexZ + 0],
                    (0 + quadIndexZ + 0) * scaleZ),
                new JVector((0 + quadIndexX + 1) * scaleX, heights[0 + quadIndexX + 1, 0 + quadIndexZ + 1],
                    (0 + quadIndexZ + 1) * scaleZ),
                new JVector((0 + quadIndexX + 0) * scaleX, heights[0 + quadIndexX + 0, 0 + quadIndexZ + 1],
                    (0 + quadIndexZ + 1) * scaleZ)
            ));
        }

        return new TriangleMesh(triangleList);
    }

    [Pure]
    public static IEnumerable<RigidBodyShape> CreateShapes(TriangleMesh triangleMesh)
    {
        for (var i = 0; i < triangleMesh.Indices.Length; i++)
        {
            yield return new FatTriangleShape(triangleMesh, i);
        }
    }

    public static RigidBody AddTerrain(this Jitter2.World world, float[,] heights, float scaleX, float scaleZ)
    {
        var terrain = world.CreateRigidBody();
        terrain.AddShape(CreateShapes(CreateMesh(heights, scaleX, scaleZ)), false);
        terrain.Position = JVector.Zero;
        terrain.IsStatic = true;

        return terrain;
    }
}

[notgiven688]

At a quick glance, that looks perfectly fine. Also, make sure that the triangles point in the correct direction (i.e., the normal is defined by the winding order, either clockwise or counterclockwise). See here: #208.