MSVC（STD：C＆＃x2B; 17）可选始终返回值

发布于 2025-01-23 07:07:54 字数 942 浏览 0 评论 0原文

我正在为射线示踪剂编写一些交叉代码。在计算球体的一些交点逻辑之后，我想返回可选的，以确定是否存在相交。我不想返回距离的“无效”值，而是要使用C ++'S std ::可选类。唯一的问题是，它似乎总是返回true for has_value（）：

std::optional<Intersection> Sphere::ray_intersection(Ray ray)
    // Calculate Intersection Logic
    // ...
    if (distance_to_intersection < 0) {
        return std::nullopt;
    } else {
        return Intersection(ray, distance_to_intersection);
    }
}

返回后，我使用以下代码检查：

if (sphere.ray_intersection(ray).has_value()) {
    return shade(sphere, intersection);
} else {
    return background_color;
}

我知道实际的交叉点逻辑正确，因为当我替换返回std :: nullopt;用返回交叉点（ray，-1）;（无效距离），然后简单地检查距离是否等于-1在上一个检查中，它的行为符合预期。

我还尝试返回简单的{}无用。

我目前正在使用Microsoft Visual Studio 2022，并且我尝试了C ++ 17和C ++ 20编译器，并且我期望的是行为。

std ::可选操作我不知道的特定方式吗？

原文

I'm writing some intersection code for a Ray tracer. After calculating some intersection logic for a sphere, I want to return an optional to determine if there was an intersection or not. Instead of returning an "invalid" value for distance, I want to use C++'s std::optional class. The only issue is that it seems to always return true for has_value():

std::optional<Intersection> Sphere::ray_intersection(Ray ray)
    // Calculate Intersection Logic
    // ...
    if (distance_to_intersection < 0) {
        return std::nullopt;
    } else {
        return Intersection(ray, distance_to_intersection);
    }
}

After returning, I check using the following code:

if (sphere.ray_intersection(ray).has_value()) {
    return shade(sphere, intersection);
} else {
    return background_color;
}

I know the actual intersection logic works correctly, because when I replace return std::nullopt; with return Intersection(ray, -1); (an invalid distance) and then simply check if the distance is equal to -1 in the previous if check, it behaves as expected.

I've also tried returning a simple {} to no avail.

I'm currently using Microsoft Visual Studio 2022, and I have tried both the C++17 and C++20 compilers, and neither will behave as I'm expecting.

Is there a specific way that std::optional operates that I'm not aware of?

分享到QQ

分享到微博