DirectX 9 Terrain genereration C++

Question

I am having trouble generating a flat terrain with quads, I think the quads are located correctly but the indices are incorrect.. Can someone please have a look see and tell me what i am doing wrong or how i can fix it? Basically the terrain is displayed but totally wrong. I THINK it is the indices positioning, please help me it would be highly appreciated.

FOR LOOP:

    for(int i = 0; i < NUM_VERTS; i += 4){
    for(int x = 0; x < j; x ++){
        for(int z = 0; z < j; z ++){
            verts[i] = D3DVertex::VertexPositionNormalTexture(x, -1.0f, z+1, n, 1.0f, g, 0.0f, 0.0f);
            verts[i+1] = D3DVertex::VertexPositionNormalTexture(x+1, -1.0f, z+1, n, 1.0f, g, 1.0f, 0.0f);
            verts[i+2] = D3DVertex::VertexPositionNormalTexture(x, -1.0f, z, n, 1.0f, g, 0.0f, 1.0f);
            verts[i+2] = D3DVertex::VertexPositionNormalTexture(x+1, -1.0f, z, n, 1.0f, g, 0.0f, 1.0f);
            indices[i] = i;
            indices[i+1] = i+1;
            indices[i+2] = i+2;
            indices[i+3] = i+2;
            indices[i+4] = i+1;
            indices[i+5] = i+3;
        }
    }
    //MessageBox(NULL, L"Test", NULL, NULL);
}

Answer 1

Your outer-most loop does not make sense. Instead, maintain two indices for the vertex buffer and the index buffer like so:

int iVertex = 0;
int iIndex = 0;
for(int x = 0; x < j; x ++){
    for(int z = 0; z < j; z ++){
        verts[iVertex  ] = D3DVertex::VertexPositionNormalTexture(x, -1.0f, z+1, n, 1.0f, g, 0.0f, 0.0f);
        verts[iVertex+1] = D3DVertex::VertexPositionNormalTexture(x+1, -1.0f, z+1, n, 1.0f, g, 1.0f, 0.0f);
        verts[iVertex+2] = D3DVertex::VertexPositionNormalTexture(x, -1.0f, z, n, 1.0f, g, 0.0f, 1.0f);
        verts[iVertex+3] = D3DVertex::VertexPositionNormalTexture(x+1, -1.0f, z, n, 1.0f, g, 0.0f, 1.0f);
        indices[iIndex  ] = iVertex;
        indices[iIndex+1] = iVertex+1;
        indices[iIndex+2] = iVertex+2;
        indices[iIndex+3] = iVertex+2;
        indices[iIndex+4] = iVertex+1;
        indices[iIndex+5] = iVertex+3;

        iVertex += 4;
        iIndex += 6;
    }
}

I assume that you're aware that the terrain will stretch from 0 to j + 1 in both x and z direction.

If it's just a plane, you might also consider using a single quad. If you need multiple triangles, you might consider converting the triangle list to a triangle strip. If you want to stick to the triangle list, you should at least consider removing the duplicate vertices (every vertex in the terrain's center exists four times).