This lesson discusses how to make use of more advanced math functions provided in the DirectXMath library using existing SimpleMath types.
would instead become:
See SimpleMath for a complete list of Matrix methods that are 'handed'.
Many 'handed' DirectX Tool Kit functions take a bool parameter rhcoords that defaults to true. You should pass false when using left-handed view coordinates.
http://en.wikipedia.org/wiki/Right-hand_rule
This compiles fine, but at runtime this actually executes a little bit of code to build the structure up. For a vector like this where all the values are literals and known at compile time, a more efficient way to code them is to use DirectXMath's XMVECTORF32 and related types:
This becomes a vector laid out properly in data memory in your program ready for immediate use.
Options here include using:
https://msdn.microsoft.com/en-us/library/windows/desktop/microsoft.directx_sdk.utilities.xmfresnelterm.aspx
For example, if we want to create the initData for a texture in DXGI_FORMAT_R9G9B9E5_SHAREDEXP format:
https://msdn.microsoft.com/en-us/library/windows/desktop/ee418728.aspx
Next lesson:Adding the DirectX Tool Kit for Audio
http://blogs.msdn.com/b/chuckw/archive/2013/10/24/directxmath-3-06.aspx
http://blogs.msdn.com/b/chuckw/archive/2014/12/12/known-issues-directxmath-3-06.aspx
http://blogs.msdn.com/b/chuckw/archive/2012/07/28/spherical-harmonics-math.aspx
http://blogs.msdn.com/b/chuckw/archive/2012/05/01/xdsp-h.aspx
http://blogs.msdn.com/b/chuckw/archive/2012/09/11/directxmath-sse-sse2-and-arm-neon.aspx
Coordinate system
The SimpleMath wrapper assumes you are using right-handed coordinates, as does the remainder of the DirectX Tool Kit consistent with the default of XNA Game Studio. DirectXMath and Direct3D 11 generally, however, supports both right-handed and left-handed coordinates. If left-handed coordinates are desired, instead of using the handed Matrix methods, you use the DirectXMath LH equivalent function.
m_view = Matrix::CreateLookAt(Vector3(2.f, 2.f, 2.f), Vector3::Zero, Vector3::UnitY);
m_proj = Matrix::CreatePerspectiveFieldOfView(XM_PI / 4.f,
viewPort.Width / viewPort.Height, 0.1f, 10.f);would instead become:
m_view = XMMatrixLookAtLH(Vector3(2.f, 2.f, 2.f), Vector3::Zero, Vector3::UnitY);
m_proj = XMMatrixPerspectiveFovLH( XM_PI / 4.f,
viewPort.Width / viewPort.Height, 0.1f, 10.f);See SimpleMath for a complete list of Matrix methods that are 'handed'.
Many 'handed' DirectX Tool Kit functions take a bool parameter rhcoords that defaults to true. You should pass false when using left-handed view coordinates.
http://en.wikipedia.org/wiki/Right-hand_rule
Constants
A convenient way to build up constants with SimpleMath is to use the C++ constructers such as:Vector3 a(10.f, -.5f, 2.5f);
This compiles fine, but at runtime this actually executes a little bit of code to build the structure up. For a vector like this where all the values are literals and known at compile time, a more efficient way to code them is to use DirectXMath's XMVECTORF32 and related types:
staticconst XMVECTORF32 s_a = { 10.f, -.5f, 2.5f, 0.f };
This becomes a vector laid out properly in data memory in your program ready for immediate use.
Options here include using:
- XMVECTORF32 which is 4x floats
- XMVECTORI32 which is 4x 32-bit ints
- XMVECTORU32 which is 4x 32-bit unsigned ints
- XMVECTORU8 which is 16x 8-bit unsigned ints
staticconst XMVECTORF32 s_lookat = { 2.f, 2.f, 2.f, 0.f }; m_view = Matrix::CreateLookAt( s_lookat, Vector3::Zero, Vector3::UnitY);
Fresnel term
Because of the free conversion of SimpleMath types, you can easily mix existing SimpleMath code with DirectXMath functions. For example, the XMFresnelTerm function doesn't have a SimpleMath equivalent:
Vector3 fresnel = XMFresnelTerm( Vector4( a1, a2, a3, a4 ),
Vector4( ri1, ri2, ri3, ri4 ) );https://msdn.microsoft.com/en-us/library/windows/desktop/microsoft.directx_sdk.utilities.xmfresnelterm.aspx
PackedVector
DirectXMath includes a large collection of types and load/store methods in the DirectX::PackedVector namespace for converting to and from numerous specialized GPU types.For example, if we want to create the initData for a texture in DXGI_FORMAT_R9G9B9E5_SHAREDEXP format:
std::unique_ptr<DirectX::PackedVector::XMFLOAT3SE]]> data(
new DirectX::PackedVector::XMFLOAT3SE[width * height] );
for ( size_t h = 0; h < height; ++h )
{
for( size_t w = 0; w < width; ++w )
{
Vector3 pixel; // our data from somewhere
XMStoreFloat3SE( &data[ w * h ], pixel );
}
}https://msdn.microsoft.com/en-us/library/windows/desktop/ee418728.aspx
Next lesson:Adding the DirectX Tool Kit for Audio
Further reading
http://blogs.msdn.com/b/chuckw/archive/2012/03/27/introducing-directxmath.aspxhttp://blogs.msdn.com/b/chuckw/archive/2013/10/24/directxmath-3-06.aspx
http://blogs.msdn.com/b/chuckw/archive/2014/12/12/known-issues-directxmath-3-06.aspx
http://blogs.msdn.com/b/chuckw/archive/2012/07/28/spherical-harmonics-math.aspx
http://blogs.msdn.com/b/chuckw/archive/2012/05/01/xdsp-h.aspx
http://blogs.msdn.com/b/chuckw/archive/2012/09/11/directxmath-sse-sse2-and-arm-neon.aspx