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-rw-r--r--libdimension/dimension/geometry.h8
-rw-r--r--libdimension/geometry.c127
-rw-r--r--tests/raytrace.c8
3 files changed, 108 insertions, 35 deletions
diff --git a/libdimension/dimension/geometry.h b/libdimension/dimension/geometry.h
index 4effea8..95692c6 100644
--- a/libdimension/dimension/geometry.h
+++ b/libdimension/dimension/geometry.h
@@ -29,12 +29,7 @@
typedef struct { double x, y, z; } dmnsn_vector;
-typedef struct {
- double n00, n01, n02, n03,
- n10, n11, n12, n13,
- n20, n21, n22, n23,
- n30, n31, n32, n33;
-} dmnsn_matrix;
+typedef struct { double n[4][4]; } dmnsn_matrix;
/* A line, or ray. */
typedef struct {
@@ -70,6 +65,7 @@ dmnsn_vector dmnsn_vector_cross(dmnsn_vector lhs, dmnsn_vector rhs);
double dmnsn_vector_norm(dmnsn_vector n);
dmnsn_vector dmnsn_vector_normalize(dmnsn_vector n);
+dmnsn_matrix dmnsn_matrix_inverse(dmnsn_matrix A);
dmnsn_matrix dmnsn_matrix_mul(dmnsn_matrix lhs, dmnsn_matrix rhs);
dmnsn_vector dmnsn_matrix_vector_mul(dmnsn_matrix lhs, dmnsn_vector rhs);
dmnsn_line dmnsn_matrix_line_mul(dmnsn_matrix lhs, dmnsn_line rhs);
diff --git a/libdimension/geometry.c b/libdimension/geometry.c
index 026932b..372a94c 100644
--- a/libdimension/geometry.c
+++ b/libdimension/geometry.c
@@ -36,10 +36,10 @@ dmnsn_matrix_construct(double a0, double a1, double a2, double a3,
double c0, double c1, double c2, double c3,
double d0, double d1, double d2, double d3)
{
- dmnsn_matrix m = { .n00 = a0, .n01 = a1, .n02 = a2, .n03 = a3,
- .n10 = b0, .n11 = b1, .n12 = b2, .n13 = b3,
- .n20 = c0, .n21 = c1, .n22 = c2, .n23 = c3,
- .n30 = d0, .n31 = d1, .n32 = d2, .n33 = d3 };
+ dmnsn_matrix m = { { { a0, a1, a2, a3 },
+ { b0, b1, b2, b3 },
+ { c0, c1, c2, c3 },
+ { d0, d1, d2, d3 } } };
return m;
}
@@ -182,31 +182,104 @@ dmnsn_vector_normalize(dmnsn_vector n)
return dmnsn_vector_div(n, dmnsn_vector_norm(n));
}
-/* 4x4 matrix multiplication */
+/* Matrix inversion helper function */
+static double dmnsn_matrix_cofactor(dmnsn_matrix A,
+ unsigned int row, unsigned int col);
+
+/* Invert a matrix */
dmnsn_matrix
-dmnsn_matrix_mul(dmnsn_matrix lhs, dmnsn_matrix rhs)
+dmnsn_matrix_inverse(dmnsn_matrix A)
{
- dmnsn_matrix r;
+ dmnsn_matrix adj;
+ double det = 0.0, C;
+ unsigned int i, j;
+
+ for (j = 0; j < 4; ++j) {
+ C = dmnsn_matrix_cofactor(A, 0, j);
+ det += A.n[0][j]*C;
+ adj.n[j][0] = C;
+ }
- r.n00 = lhs.n00*rhs.n00 + lhs.n01*rhs.n10 + lhs.n02*rhs.n20 + lhs.n03*rhs.n30;
- r.n01 = lhs.n00*rhs.n01 + lhs.n01*rhs.n11 + lhs.n02*rhs.n21 + lhs.n03*rhs.n31;
- r.n02 = lhs.n00*rhs.n02 + lhs.n01*rhs.n12 + lhs.n02*rhs.n22 + lhs.n03*rhs.n32;
- r.n03 = lhs.n00*rhs.n03 + lhs.n01*rhs.n13 + lhs.n02*rhs.n23 + lhs.n03*rhs.n33;
+ for (j = 0; j < 4; ++j) {
+ adj.n[j][0] /= det;
+ }
- r.n10 = lhs.n10*rhs.n00 + lhs.n11*rhs.n10 + lhs.n12*rhs.n20 + lhs.n13*rhs.n30;
- r.n11 = lhs.n10*rhs.n01 + lhs.n11*rhs.n11 + lhs.n12*rhs.n21 + lhs.n13*rhs.n31;
- r.n12 = lhs.n10*rhs.n02 + lhs.n11*rhs.n12 + lhs.n12*rhs.n22 + lhs.n13*rhs.n32;
- r.n13 = lhs.n10*rhs.n03 + lhs.n11*rhs.n13 + lhs.n12*rhs.n23 + lhs.n13*rhs.n33;
+ for (i = 1; i < 4; ++i) {
+ for (j = 0; j < 4; ++j) {
+ adj.n[j][i] = dmnsn_matrix_cofactor(A, i, j)/det;
+ }
+ }
+
+ return adj;
+}
- r.n20 = lhs.n20*rhs.n00 + lhs.n21*rhs.n10 + lhs.n22*rhs.n20 + lhs.n23*rhs.n30;
- r.n21 = lhs.n20*rhs.n01 + lhs.n21*rhs.n11 + lhs.n22*rhs.n21 + lhs.n23*rhs.n31;
- r.n22 = lhs.n20*rhs.n02 + lhs.n21*rhs.n12 + lhs.n22*rhs.n22 + lhs.n23*rhs.n32;
- r.n23 = lhs.n20*rhs.n03 + lhs.n21*rhs.n13 + lhs.n22*rhs.n23 + lhs.n23*rhs.n33;
+/* Gives the cofactor at row, col; the determinant of the matrix formed from A
+ by ignoring row `row' and column `col', times (-1)**(row + col) */
+static double
+dmnsn_matrix_cofactor(dmnsn_matrix A, unsigned int row, unsigned int col)
+{
+ double n[9], C;
+ unsigned int i, j, k = 0;
+
+ for (i = 0; i < 4; ++i) {
+ for (j = 0; j < 4; ++j) {
+ if (i != row && j != col) {
+ n[k] = A.n[i][j];
+ ++k;
+ }
+ }
+ }
+
+ C = n[0]*(n[4]*n[8] - n[5]*n[7]) + n[1]*(n[5]*n[6] - n[3]*n[8])
+ + n[2]*(n[3]*n[7] - n[4]*n[6]);
+ if ((row + col)%2 == 0) {
+ return C;
+ } else {
+ return -C;
+ }
+}
+
+/* 4x4 matrix multiplication */
+dmnsn_matrix
+dmnsn_matrix_mul(dmnsn_matrix lhs, dmnsn_matrix rhs)
+{
+ dmnsn_matrix r;
- r.n30 = lhs.n30*rhs.n00 + lhs.n31*rhs.n10 + lhs.n32*rhs.n20 + lhs.n33*rhs.n30;
- r.n31 = lhs.n30*rhs.n01 + lhs.n31*rhs.n11 + lhs.n32*rhs.n21 + lhs.n33*rhs.n31;
- r.n32 = lhs.n30*rhs.n02 + lhs.n31*rhs.n12 + lhs.n32*rhs.n22 + lhs.n33*rhs.n32;
- r.n33 = lhs.n30*rhs.n03 + lhs.n31*rhs.n13 + lhs.n32*rhs.n23 + lhs.n33*rhs.n33;
+ r.n[0][0] = lhs.n[0][0]*rhs.n[0][0] + lhs.n[0][1]*rhs.n[1][0]
+ + lhs.n[0][2]*rhs.n[2][0] + lhs.n[0][3]*rhs.n[3][0];
+ r.n[0][1] = lhs.n[0][0]*rhs.n[0][1] + lhs.n[0][1]*rhs.n[1][1]
+ + lhs.n[0][2]*rhs.n[2][1] + lhs.n[0][3]*rhs.n[3][1];
+ r.n[0][2] = lhs.n[0][0]*rhs.n[0][2] + lhs.n[0][1]*rhs.n[1][2]
+ + lhs.n[0][2]*rhs.n[2][2] + lhs.n[0][3]*rhs.n[3][2];
+ r.n[0][3] = lhs.n[0][0]*rhs.n[0][3] + lhs.n[0][1]*rhs.n[1][3]
+ + lhs.n[0][2]*rhs.n[2][3] + lhs.n[0][3]*rhs.n[3][3];
+
+ r.n[1][0] = lhs.n[1][0]*rhs.n[0][0] + lhs.n[1][1]*rhs.n[1][0]
+ + lhs.n[1][2]*rhs.n[2][0] + lhs.n[1][3]*rhs.n[3][0];
+ r.n[1][1] = lhs.n[1][0]*rhs.n[0][1] + lhs.n[1][1]*rhs.n[1][1]
+ + lhs.n[1][2]*rhs.n[2][1] + lhs.n[1][3]*rhs.n[3][1];
+ r.n[1][2] = lhs.n[1][0]*rhs.n[0][2] + lhs.n[1][1]*rhs.n[1][2]
+ + lhs.n[1][2]*rhs.n[2][2] + lhs.n[1][3]*rhs.n[3][2];
+ r.n[1][3] = lhs.n[1][0]*rhs.n[0][3] + lhs.n[1][1]*rhs.n[1][3]
+ + lhs.n[1][2]*rhs.n[2][3] + lhs.n[1][3]*rhs.n[3][3];
+
+ r.n[2][0] = lhs.n[2][0]*rhs.n[0][0] + lhs.n[2][1]*rhs.n[1][0]
+ + lhs.n[2][2]*rhs.n[2][0] + lhs.n[2][3]*rhs.n[3][0];
+ r.n[2][1] = lhs.n[2][0]*rhs.n[0][1] + lhs.n[2][1]*rhs.n[1][1]
+ + lhs.n[2][2]*rhs.n[2][1] + lhs.n[2][3]*rhs.n[3][1];
+ r.n[2][2] = lhs.n[2][0]*rhs.n[0][2] + lhs.n[2][1]*rhs.n[1][2]
+ + lhs.n[2][2]*rhs.n[2][2] + lhs.n[2][3]*rhs.n[3][2];
+ r.n[2][3] = lhs.n[2][0]*rhs.n[0][3] + lhs.n[2][1]*rhs.n[1][3]
+ + lhs.n[2][2]*rhs.n[2][3] + lhs.n[2][3]*rhs.n[3][3];
+
+ r.n[3][0] = lhs.n[3][0]*rhs.n[0][0] + lhs.n[3][1]*rhs.n[1][0]
+ + lhs.n[3][2]*rhs.n[2][0] + lhs.n[3][3]*rhs.n[3][0];
+ r.n[3][1] = lhs.n[3][0]*rhs.n[0][1] + lhs.n[3][1]*rhs.n[1][1]
+ + lhs.n[3][2]*rhs.n[2][1] + lhs.n[3][3]*rhs.n[3][1];
+ r.n[3][2] = lhs.n[3][0]*rhs.n[0][2] + lhs.n[3][1]*rhs.n[1][2]
+ + lhs.n[3][2]*rhs.n[2][2] + lhs.n[3][3]*rhs.n[3][2];
+ r.n[3][3] = lhs.n[3][0]*rhs.n[0][3] + lhs.n[3][1]*rhs.n[1][3]
+ + lhs.n[3][2]*rhs.n[2][3] + lhs.n[3][3]*rhs.n[3][3];
return r;
}
@@ -219,10 +292,10 @@ dmnsn_matrix_vector_mul(dmnsn_matrix lhs, dmnsn_vector rhs)
dmnsn_vector r;
double w;
- r.x = lhs.n00*rhs.x + lhs.n01*rhs.y + lhs.n02*rhs.z + lhs.n03;
- r.y = lhs.n10*rhs.x + lhs.n11*rhs.y + lhs.n12*rhs.z + lhs.n13;
- r.z = lhs.n20*rhs.x + lhs.n21*rhs.y + lhs.n22*rhs.z + lhs.n23;
- w = lhs.n30*rhs.x + lhs.n31*rhs.y + lhs.n32*rhs.z + lhs.n33;
+ r.x = lhs.n[0][0]*rhs.x + lhs.n[0][1]*rhs.y + lhs.n[0][2]*rhs.z + lhs.n[0][3];
+ r.y = lhs.n[1][0]*rhs.x + lhs.n[1][1]*rhs.y + lhs.n[1][2]*rhs.z + lhs.n[1][3];
+ r.z = lhs.n[2][0]*rhs.x + lhs.n[2][1]*rhs.y + lhs.n[2][2]*rhs.z + lhs.n[2][3];
+ w = lhs.n[3][0]*rhs.x + lhs.n[3][1]*rhs.y + lhs.n[3][2]*rhs.z + lhs.n[3][3];
return dmnsn_vector_div(r, w);
}
diff --git a/tests/raytrace.c b/tests/raytrace.c
index c8c25cd..ea5b67f 100644
--- a/tests/raytrace.c
+++ b/tests/raytrace.c
@@ -59,11 +59,15 @@ int main() {
scene->background = color;
sphere = dmnsn_new_sphere();
- sphere->trans = dmnsn_scale_matrix(dmnsn_vector_construct(0.8, 0.8, 0.8));
+ sphere->trans = dmnsn_matrix_inverse(
+ dmnsn_scale_matrix(dmnsn_vector_construct(1.25, 1.25, 1.25))
+ );
dmnsn_array_push(scene->objects, &sphere);
cube = dmnsn_new_cube();
- cube->trans = dmnsn_rotation_matrix(dmnsn_vector_construct(0.75, 0.0, 0.0));
+ cube->trans = dmnsn_matrix_inverse(
+ dmnsn_rotation_matrix(dmnsn_vector_construct(0.75, 0.0, 0.0))
+ );
dmnsn_array_push(scene->objects, &cube);
dmnsn_raytrace_scene(scene);
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-06 14:11:51 +0000