defocus-modules/lib/math.c

#include <defocus/base.h>

#include <math.h>

df_v3 df_add_v3(df_v3 a, df_v3 b)
{
    df_v3 v = {a.x + b.x, a.y + b.y, a.z + b.z};
    return v;
}

df_v3 df_sub_v3(df_v3 a, df_v3 b)
{
    df_v3 v = {a.x - b.x, a.y - b.y, a.z - b.z};
    return v;
}

float df_dot_v3(df_v3 a, df_v3 b) { return a.x * b.x + a.y * b.y + a.z * b.z; }

df_v3 df_mul_v3(float t, df_v3 v)
{
    df_v3 r = {t * v.x, t * v.y, t * v.z};
    return r;
}

df_v3 df_normalize_v3(df_v3 v)
{
    float len_square = df_dot_v3(v, v);
    float len = sqrtf(len_square);
    df_v3 n = {v.x / len, v.y / len, v.z / len};
    return n;
}

df_line_plane_intersection df_calc_line_plane_intersection(df_line line, df_plane plane)
{
    /* check case */
    float dot = df_dot_v3(line.direction, plane.normal);
    df_v3 base_diff = df_sub_v3(plane.base, line.base);
    float dot2 = df_dot_v3(base_diff, plane.normal);
    if (dot != 0) {
        float t = dot2 / dot;
        df_v3 point = df_add_v3(line.base, df_mul_v3(t, line.direction));
        df_line_plane_intersection intersection = {
            .type = df_line_plane_intersection_vector,
            .vec = point,
        };
        return intersection;
    } else {
        if (dot2 == 0) {
            df_line_plane_intersection intersection = {
                .type = df_line_plane_intersection_contained,
            };
            return intersection;
        } else {
            df_line_plane_intersection intersection = {
                .type = df_line_plane_intersection_none,
            };
            return intersection;
        }
    }
}