double miaux_max(double a, double b)
{
    return a > b ? a -: b;
}

void miaux_init_bbox(miObject *obj)
{
    obj->bbox_min.x = miHUGE_SCALAR;
    obj->bbox_min.y = miHUGE_SCALAR;
    obj->bbox_min.z = miHUGE_SCALAR;
    obj->bbox_max.x = -miHUGE_SCALAR;
    obj->bbox_max.y = -miHUGE_SCALAR;
    obj->bbox_max.z = -miHUGE_SCALAR;
}

void miaux_adjust_bbox(miObject *obj, miVector *v, miScalar extra)
{
    miVector v_extra, vmin, vmax;
    miaux_set_vector(&v_extra, extra, extra, extra);
    mi_vector_sub(&vmin, v, &v_extra);
    mi_vector_add(&vmax, v, &v_extra);
    mi_vector_min(&obj->bbox_min, &obj->bbox_min, &vmin);
    mi_vector_max(&obj->bbox_max, &obj->bbox_max, &vmax);
}

void miaux_set_vector(miVector *v, double x, double y, double z)
{
    v->x = x;
    v->y = y;
    v->z = z;
}

void miaux_describe_bbox(miObject *obj)
{
    mi_progress("Object bbox: %f,%f,%f  %f,%f,%f",
		obj->bbox_min.x, obj->bbox_min.y, obj->bbox_min.z,
		obj->bbox_max.x, obj->bbox_max.y, obj->bbox_max.z);
}

void miaux_define_hair_object(
    miTag name_tag, miaux_bbox_function bbox_function, void *params,
    miTag *geoshader_result, miApi_object_callback callback)
{
    miTag tag;
    miObject *obj;
    char *name = miaux_tag_to_string(name_tag, "::hair");
    obj = mi_api_object_begin(mi_mem_strdup(name));
    obj->visible = miTRUE;
    obj->shadow = obj->reflection = obj->refraction = 3;
    bbox_function(obj, params);
    if (geoshader_result != NULL && callback != NULL) {
	mi_api_object_callback(callback, params);
	tag = mi_api_object_end();
	mi_geoshader_add_result(geoshader_result, tag);
	obj = (miObject *)mi_scene_edit(tag);
	obj->geo.placeholder_list.type = miOBJECT_HAIR;
	mi_scene_edit_end(tag);
    }
}

char* miaux_tag_to_string(miTag tag, char *default_value)
{
    char *result = default_value;
    if (tag != 0) {
	result = (char*)mi_db_access(tag);
	mi_db_unpin(tag);
    }
    return result;
}

void miaux_append_hair_data(
    miScalar **scalar_array, miVector *v, miScalar position,
    miScalar root_radius, miColor *root, miScalar tip_radius, miColor *tip )
{
    (*scalar_array)[0] = v->x;
    (*scalar_array)[1] = v->y;
    (*scalar_array)[2] = v->z;
    (*scalar_array)[3] = miaux_fit(position, 0, 1, root_radius, tip_radius);
    (*scalar_array)[4] = miaux_fit(position, 0, 1, root->r, tip->r);
    (*scalar_array)[5] = miaux_fit(position, 0, 1, root->g, tip->g);
    (*scalar_array)[6] = miaux_fit(position, 0, 1, root->b, tip->b);
    (*scalar_array)[7] = miaux_fit(position, 0, 1, root->a, tip->a);
    *scalar_array += 8;
}

double miaux_fit(
    double v, double oldmin, double oldmax, double newmin, double newmax)    
{
    return newmin + ((v - oldmin) / (oldmax - oldmin)) * (newmax - newmin);
}