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use math;
export fn ortho(
m: *m4,
left: f32,
right: f32,
bottom: f32,
top: f32,
znear: f32,
zfar: f32,
) void = {
m4_set_zero(m);
const rl = 1.0 / (right - left);
const tb = 1.0 / (top - bottom);
const nf = -1.0 / (zfar - znear);
m[0][0] = 2.0 * rl;
m[1][1] = 2.0 * tb;
m[2][2] = 2.0 * nf;
m[3][0] =-(right + left) * rl;
m[3][1] =-(top + bottom) * tb;
m[3][2] = (zfar + znear) * nf;
m[3][3] = 1.0;
};
export fn lookat(eye: *v3, center: *v3, up: *v3) m4 = {
const f = v3_sub(center, eye);
v3_normalize(&f);
const s = v3_crossn(&f, up);
const u = v3_cross(&s, &f);
const res = m4_new(1.0);
res[0][0] = s[0];
res[0][1] = u[0];
res[0][2] = -f[0];
res[1][0] = s[1];
res[1][1] = u[1];
res[1][2] = -f[1];
res[2][0] = s[2];
res[2][1] = u[2];
res[2][2] = -f[2];
res[3][0] = -v3_dot(&s, eye);
res[3][1] = -v3_dot(&u, eye);
res[3][2] = v3_dot(&f, eye);
res[0][3] = 0.0;
res[1][3] = 0.0;
res[2][3] = 0.0;
res[3][3] = 1.0;
return res;
};
export fn perspective(
m: *m4,
fovy_in_deg: f32,
aspect_ratio: f32,
znear: f32,
zfar: f32
) void = {
m4_set_zero(m);
const f = 1.0 / math::tanf64(fovy_in_deg * 0.5): f32;
const f1 = 1.0 / (znear - zfar);
m[0][0] = f / aspect_ratio;
m[1][1] = f;
m[2][2] = (znear + zfar) * f1;
m[2][3] = -1.0;
m[3][2] = 2.0 * znear * zfar * f1;
};
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