UKismetMathLibrary::Matrix_GetDeterminant

function Engine Blueprint Since 4.0

#include "Kismet/KismetMathLibrary.h"

Access: public Specifiers: staticBlueprintPure

Description

Computes the determinant of the full 4x4 matrix. The determinant indicates volume scaling and whether the matrix is invertible (determinant near zero means singular).

Caveats & Gotchas

• A determinant of zero (or near zero) means the matrix is singular and has no inverse — calling Matrix_GetInverse on such a matrix will return a zero or garbage matrix.
• Negative determinants indicate a reflection (mirrored transform). This matters for face winding: a negative-determinant transform matrix will flip triangle winding order, causing backface culling to cull the wrong faces.

Signature

static UE_INL_API float Matrix_GetDeterminant(const FMatrix& M)

Parameters

Name	Type	Description	Default
M	const FMatrix&	The matrix whose determinant to compute.	—

Return Type

float

Example

Guard against singular matrix before inverting C++

float Det = UKismetMathLibrary::Matrix_GetDeterminant(M);
if (FMath::Abs(Det) > SMALL_NUMBER)
{
    FMatrix Inv = UKismetMathLibrary::Matrix_GetInverse(M);
    // safe to use Inv
}

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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