Question

I’m having trouble using Short2 for the (x,y) positions in my vertex data. This is my vertex structure:

struct VertexPositionShort : IVertexType
{
    private static VertexElement[]
        vertexElements = new VertexElement[]
        {
            new VertexElement(0, VertexElementFormat.Short2, VertexElementUsage.Position, 0),
        };
    private static VertexDeclaration
        vertexDeclaration = new VertexDeclaration(vertexElements);

    public Short2
        Position;


    public static VertexDeclaration Declaration
    {
        get { return new VertexDeclaration(vertexElements); }
    }

    VertexDeclaration IVertexType.VertexDeclaration
    {
        get { return new VertexDeclaration(vertexElements); }
    }
}

Using the WP7 emulator, nothing is drawn if I use this structure – no artifacts, nothing! However, if I use an identical structure where the Short2 structs are replaced by Vector2 then it all works perfectly.

I’ve found a reference to this being an emulator-specific issue: “In the Windows Phone Emulator, the SkinnedEffect bone index channel must be specified as one of the integer vertex element formats – either Byte4, Short2, or Short4. This same set of integer data formats cannot be used for other shader input channels such as colors, positions, and texture coordinates on the emulator.” (http://www.softpedia.com/progChangelog/Windows-Phone-Developer-Tools-Changelog-154611.html) However this is from July 2010 and I’d have assumed this limitation has been fixed by now…? Unfortunately I don’t have a device to test on.

Can anyone confirm that this is still an issue in the emulator or point me at another reason why this is not working?

Answer 1

Solved, by Mr Shawn Hargreaves: “You can use Short2 in vertex data, but this is an integer type, so your vertex shader must be written to accept integer rather than float inputs. BasicEffect takes floats, so Short2 will not work with it. NormalizedShort2 might be a better choice?”

http://blogs.msdn.com/b/shawnhar/archive/2010/11/19/compressed-vertex-data.aspx

I can confirm that NormalizedShort2 does in fact work for position data, in both the WP7 emulator and on real devices.

Thanks, Shawn!