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Implement Mat4x4::LookAt

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josh
2024-02-01 17:27:32 -05:00
parent c858d3b889
commit 69ca7c5c05
2 changed files with 40 additions and 0 deletions
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31
include/J3ML/LinearAlgebra/Matrix4x4.h
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@@ -65,6 +65,37 @@ namespace LinearAlgebra {
/// Logically, the translation occurs after the rotation has been performed.
Matrix4x4(const Quaternion& orientation, const Vector3 &translation);
/// Creates a LookAt matrix from a look-at direction vector.
/** A LookAt matrix is a rotation matrix that orients an object to face towards a specified target direction.
@param localForward Specifies the forward direction in the local space of the object. This is the direction
the model is facing at in its own local/object space, often +X (1,0,0), +Y (0,1,0) or +Z (0,0,1). The
vector to pass in here depends on the conventions you or your modeling software is using, and it is best
pick one convention for all your objects, and be consistent.
This input parameter must be a normalized vector.
@param targetDirection Specifies the desired world space direction the object should look at. This function
will compute a rotation matrix which will rotate the localForward vector to orient towards this targetDirection
vector. This input parameter must be a normalized vector.
@param localUp Specifies the up direction in the local space of the object. This is the up direction the model
was authored in, often +Y (0,1,0) or +Z (0,0,1). The vector to pass in here depends on the conventions you
or your modeling software is using, and it is best to pick one convention for all your objects, and be
consistent. This input parameter must be a normalized vector. This vector must be perpendicular to the
vector localForward, i.e. localForward.Dot(localUp) == 0.
@param worldUp Specifies the global up direction of the scene in world space. Simply rotating one vector to
coincide with another (localForward->targetDirection) would cause the up direction of the resulting
orientation to drift (e.g. the model could be looking at its target its head slanted sideways). To keep
the up direction straight, this function orients the localUp direction of the model to point towards the
specified worldUp direction (as closely as possible). The worldUp and targetDirection vectors cannot be
collinear, but they do not need to be perpendicular either.
@return A matrix that maps the given local space forward direction vector to point towards the given target
direction, and the given local up direction towards the given target world up direction. The returned
matrix M is orthonormal with a determinant of +1. For the matrix M it holds that
M * localForward = targetDirection, and M * localUp lies in the plane spanned by the vectors targetDirection
and worldUp.
@note The position of (the translation performed by) the resulting matrix will be set to (0,0,0), i.e. the object
will be placed to origin. Call SetTranslatePart() on the resulting matrix to set the position of the model.
@see RotateFromTo(). */
static Matrix4x4 LookAt(const Vector3& localFwd, const Vector3& targetDir, const Vector3& localUp, const Vector3& worldUp);
/// Returns the translation part.
/** The translation part is stored in the fourth column of this matrix.
This is equivalent to decomposing this matrix in the form M = T * M', i.e. this translation is applied last,

9
src/J3ML/LinearAlgebra/Matrix4x4.cpp
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@@ -419,4 +419,13 @@ namespace LinearAlgebra {
Vector3 Matrix4x4::GetTranslatePart() const {
return GetColumn3(3);
}
Matrix4x4
Matrix4x4::LookAt(const Vector3 &localFwd, const Vector3 &targetDir, const Vector3 &localUp, const Vector3 &worldUp) {
Matrix4x4 m;
m.Set3x3Part(Matrix3x3::LookAt(localFwd, targetDir, localUp, worldUp));
m.SetTranslatePart(0,0,0);
m.SetRow(3, 0,0,0,1);
return m;
}
}