Question

I’ve just recently started using XNA and now I face a beginners problem, performance. The objects I draw has their own vertex buffer, so when I have ~50k objects, the fps goes down dramatically (from 60 to 5-12).

I got the tip that I should merge my vertices into chunks, but I don’t know how to do that..

Would appreciate any help I can get with code examples.

Edit: This is the code I came up with, with help from Blau

var cubes = newChunk.Where(c => c != null && !badIndex.Contains(c.BlockType));
VertexPositionColorTextureNormal[] verts = new VertexPositionColorTextureNormal[cubes.Sum(c => c.Vertices.Count)];
int VertexOffset = 0;
var inTheRightOrder = cubes;
foreach (var cube in inTheRightOrder)
{
    var cb = cube.Vertices.ToArray();
    for (int v = 0; v < cb.Length; v++)
    {
        verts[VertexOffset + v] = cb[v];
    }

    VertexOffset += cb.Length;
}
VertexBuffer newVB = new VertexBuffer(device, VertexPositionColorTextureNormal.VertexDeclaration, verts.Length, BufferUsage.WriteOnly);
newVB.SetData(verts);
var ck = new Cube { Vertices = verts, BoundingBox = BoundingBox.CreateFromPoints(verts.Select(i => i.Position)), Buffer = newVB, Cubes = cubes.Count() };
Cubes.Add(ck);

Answer 1

To merge them you have to something similar to this.

int NumVerts = Objects.Sum(o => o.Vertex.Length);
int NumIndexes = Objects.Sum(o => o.Index.Length);

VertexPositionColor[] Vertex = new VertexPositionColor[NumVerts];
int[] Index = new int[NumIndexes];

int VertexOffset = 0;
int IndexOffset = 0;
foreach (Object object in Objects)
{
    for (int v=0; v<object.Vertex.Length; v++)
    {
        Vertex[VertexOffset+v] = object.Vertex[v] + VertexOffset;
    }

    for (int i=0; i<object.Index.Length; i++)
    {
        Index[IndexOffset+i] = object.Index[i] + VertexOffset;
    }

    VertexOffset += object.Vertex.Length;
    IdnexOffset += object.Index.Length;
}