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Adjucate calculationf for mat3 and mat2

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Imbus 2025-05-23 22:14:06 +02:00
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linalg/main.c
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@ -7,6 +7,8 @@
* Simple linear algebra mat/vec operations
*
* TODO: Normalizations
* TODO: Ensure suitable test coverade
* TODO: Mat3 adjoint should use a cofactor and a transpose function
*/
/**
@ -200,11 +202,36 @@ bool vec3_approx_eq(const Vec3 *a, const Vec3 *b, float epsilon);
*/
bool vec2_approx_eq(const Vec2 *a, const Vec2 *b, float epsilon);
/**
* @brief Computes the adjugate (adjoint) of a 2x2 matrix.
*
* The adjugate of a 2x2 matrix is obtained by swapping the diagonal elements
* and negating the off-diagonal elements.
*
* @param m Pointer to the 2x2 matrix.
* @return The adjugate of the input matrix.
*/
Mat2 mat2_adj(const Mat2 *m);
/**
* @brief Computes the adjugate (adjoint) of a 3x3 matrix.
*
* The adjugate of a 3x3 matrix is the transpose of its cofactor matrix.
* It is used in computing the inverse of the matrix.
*
* @param m Pointer to the 3x3 matrix.
* @return The adjugate of the input matrix.
*/
Mat3 mat3_adj(const Mat3 *m);
#define MAT2_AT(m, row, col) ((m)->arr[(col) * 2 + (row)])
#define MAT3_AT(m, row, col) ((m)->arr[(col) * 3 + (row)])
/* Header end... */
/* Row major */
#define MAT2_DET(a, b, c, d) ((a) * (d) - (b) * (c))
float mat3_det(const Mat3 *m) {
float m00 = MAT3_AT(m, 0, 0);
float m01 = MAT3_AT(m, 0, 1);
@ -361,6 +388,45 @@ bool vec3_approx_eq(const Vec3 *a, const Vec3 *b, float epsilon) {
(fabsf(a->z - b->z) <= epsilon);
}
Mat2 mat2_adj(const Mat2 *m) {
Mat2 res;
MAT2_AT(&res, 0, 0) = MAT2_AT(m, 1, 1);
MAT2_AT(&res, 0, 1) = -MAT2_AT(m, 0, 1);
MAT2_AT(&res, 1, 0) = -MAT2_AT(m, 1, 0);
MAT2_AT(&res, 1, 1) = MAT2_AT(m, 0, 0);
return res;
}
Mat3 mat3_adj(const Mat3 *m) {
Mat3 res;
const float a = MAT3_AT(m, 0, 0);
const float b = MAT3_AT(m, 0, 1);
const float c = MAT3_AT(m, 0, 2);
const float d = MAT3_AT(m, 1, 0);
const float e = MAT3_AT(m, 1, 1);
const float f = MAT3_AT(m, 1, 2);
const float g = MAT3_AT(m, 2, 0);
const float h = MAT3_AT(m, 2, 1);
const float i = MAT3_AT(m, 2, 2);
MAT3_AT(&res, 0, 0) = MAT2_DET(e, f, h, i);
MAT3_AT(&res, 1, 0) = -MAT2_DET(d, f, g, i);
MAT3_AT(&res, 2, 0) = MAT2_DET(d, e, g, h);
MAT3_AT(&res, 0, 1) = -MAT2_DET(b, c, h, i);
MAT3_AT(&res, 1, 1) = MAT2_DET(a, c, g, i);
MAT3_AT(&res, 2, 1) = -MAT2_DET(a, b, g, h);
MAT3_AT(&res, 0, 2) = MAT2_DET(b, c, e, f);
MAT3_AT(&res, 1, 2) = -MAT2_DET(a, c, d, f);
MAT3_AT(&res, 2, 2) = MAT2_DET(a, b, d, e);
return res;
}
/* Implem end */
int main(void) {