When we changed SCNMatrix4 to be column-major instead of row-major in .NET, there
were several other related changes we should have done but didn't do. In particular
we should have made transformation operations based on column-vectors instead of
row-vectors.
In legacy Xamarin, a vector would be transformed by a transformation matrix by doing
matrix multiplication like this:
[ x y z w] * [ 11 21 31 41 ]
| 12 22 32 42 |
| 13 23 33 43 |
[ 14 24 34 41 ]
In this case the vector is a row-vector, and it's the left operand in the multiplication.
When using column-major matrices, we want to use column-vectors, where the vector
is the right operand, like this:
[ 11 21 31 41 ] * [ x ]
| 12 22 32 42 | | y |
| 13 23 33 43 | | z |
[ 14 24 34 41 ] [ w ]
This affects numerous APIs in SCNMatrix4, SCNVector3 and SCNVector4:
* The M## fields have been changed to make the first number the column and the
second number the row, to reflect that it's a column-major matrix (this is
also how it's defined in the native SCNMatrix4 type).
* Functions that return a transformation matrix have been modified to return column-vector
transformers. Technically this means that these matrices are transposed compared
to legacy Xamarin. The functions involved are:
* CreateFromAxisAngle
* CreateRotation[X|Y|Z]
* CreateTranslation
* CreatePerspectiveFieldOfView
* CreatePerspectiveOffCenter
* Rotate
* LookAt
* Combining two column-vector transforming transformation matrices is done by multiplying
them in the reverse order, so the Mult function (and the multiplication operator)
have been modified to multiply the given matrices in the opposite order (this matches
how the SCNMatrix4Mult function does it). To make things clearer I've changed the
parameter names for XAMCORE_5_0.
* Functions that transform a vector using a transformation matrix have been modified
to do a column-vector transformation instead of a row-vector transformation. This
involves the following functions:
* SCNVector3.TransformVector
* SCNVector3.TransformNormal
* SCNVector3.TransformNormalInverse
* SCNVector3.TransformPosition
* SCNVector4.Transform
* Numerous new tests.
Fixes https://github.com/xamarin/xamarin-macios/issues/15094.
* Remove ObjCRuntime.nfloat (in favor of System.Runtime.InteropServices.NFloat).
* Automatically add a reference to the System.Runtime.InteropServices.Internal
package, so that developers get the new NFloat API (with operators) we've
added post .NET 6 (but don't do this for .NET 7).
* Automatically add a global using alias for
System.Runtime.InteropServices.NFloat -> nfloat. This is not behind the
usual `ImplicitUsings` condition our other implicit usings are, because
they're off by default for existing projects, and the main target for the
global using alias for nfloat is upgraded projects.
* Automatically generate a global using alias (like above) in the generator
for all code the generator compiles.
* Update xtro entries to reference System.Runtime.InteropServices.NFloat
instead of ObjCRuntime.nfloat.
* Add a workaround for a hopefully temporary issue with .NET/CoreCLR where the
wrong runtime pack is selected otherwise (without the new NFloat API, so
nothing works at runtime).
Ref: https://github.com/xamarin/xamarin-macios/issues/13087
fixes#13160
- remove unused types
- use System.Numerics when possible
- move own created types from OpenTK namespace to CoreGraphics
- create missing types in CoreGraphics namespace
Co-authored-by: Rolf Bjarne Kvinge <rolf@xamarin.com>
* Implement a column-major version of SCNMatrix4 in .NET to match native code.
* This was done by copying the existing SCMatrix4 implementation, and modify it
as required (doing it with conditional compilation in the same file turned out
to be quite messy, so I opted for using different files for legacy Xamarin and
.NET).
* There was one major change: the matrix inversion algorithm is new (copied from
.NET instead), because the legacy Xamarin version showed strange results with
some test values.
* Add setters for SCNMatrix4.Column[0-3] for legacy Xamarin to match the .NET API.
* Add CreateFromColumns methods for legacy Xamarin to match the .NET API.
* Add tests for all the new API.
Fixes https://github.com/xamarin/xamarin-macios/issues/4652.
Rolf Bjarne Kvinge
Stephane Delcroix