il_mat il_mat_transpose(il_mat a)
{
il_mat res = il_mat_identity();
int x, y;
for (y = 0; y < 4; y++) {
for (x = 0; x < 4; x++) {
res.data[y*4 + x] = a.data[x*4 + y];
}
}
return res;
}
il_mat il_mat_invert(il_mat a)
{
il_mat res = il_mat_identity();
// for every column ..
for (int col = 0; col < 4; ++col) {
float diagonalfield = a.data[col*4+col];
// if we have a weird matrix with zero on the diagonal ..
float eps = 0.0001;
if (fabs(diagonalfield) < eps) {
// SIIIGH.
// Okay, let's go hunting for a row with a better diagonal to use
// keep in mind, row swapping is also a linear operation!
for (int row = 0; row < 4; ++row) if (row != col) if (fabs(a.data[row*4+col]) >= eps) {
swaprow(&a, row, col);
swaprow(&res,row, col);
}
diagonalfield = a.data[col*4+col]; // recompute
// if it still fails, we probably have a denatured matrix and are proper f****d.
assert(fabs(diagonalfield) >= eps);
}
// for every row ..
for (int row = 0; row < 4; ++row) {
// if it's not on the diagonal ..
if (row != col) {
float field = a.data[row*4+col];
// bring this field to 0 by subtracting the row that's on the diagonal for this column
addrow(&a, /* src */ col, /* dst */ row, /* factor */ -field/diagonalfield);
// do the same to identity
addrow(&res,/* src */ col, /* dst */ row, /* factor */ -field/diagonalfield);
}
}
// and finally, bring the diagonal to 1
mulrow(&a, col, 1/diagonalfield);
mulrow(&res,col, 1/diagonalfield);
}
// Success! Because a is now id, res is now a^-1. Math is fun!
return res;
}
void camera_init(void *self)
{
ilG_camera* camera = self;
camera->projection_matrix = il_mat_identity(NULL);
camera->sensitivity = 0.002;
}
