{"topic":{"id":7099,"title":"2.4 generate_ray 和 naive_intersect","slug":"topic","categoryId":56,"createdAt":"2023-11-07 11:34:23.210189","bumpedAt":"2023-12-23 07:55:27.408837","views":597,"postsCount":9,"highestPostNumber":9,"likeCount":0,"closed":true,"pinned":false,"pinnedGlobally":false,"pinnedAt":null,"pinnedUntil":null,"isBanner":false,"excerpt":"请问我按照文档这样写的错误在什么地方，得到的返回值与使用 ray.cpp 的静态链接版本所得到的有些不一样并且运行时会出现 abort() has been called 的错误 (已经修改很多次了还是不行) 😭 已经进行试验：使用 ray.cpp 静态链接的话就能得到正确的渲染图","deletedAt":null,"isAnonymous":false,"category":{"id":56,"name":"计算机图形学","slug":"cg","color":"92278F"},"author":{"id":1081,"username":"KON","name":null,"avatarUrl":"/uploads/image/9f/35/9f3549f065dc7f323da5ebdb5fce01f65bbf19dbd566d5b3d817a08a7b59e7fd.avif"},"tags":[]},"posts":[{"id":16481,"postNumber":1,"raw":"请问我按照文档这样写的错误在什么地方，得到的返回值与使用 `ray.cpp` 的静态链接版本所得到的有些不一样\n并且运行时会出现 `abort() has been called` 的错误\n(已经修改很多次了还是不行) :loudly_crying_face:\n\n![code|690x269](/uploads/image/52/1c/521ce038212b8c88af381e0c529ab9463cc8908e2ebc2db34ba3f607af57d4f9.avif)\n\n已经进行试验：使用 `ray.cpp` 静态链接的话就能得到正确的渲染图","cooked":"

请问我按照文档这样写的错误在什么地方，得到的返回值与使用 ray.cpp 的静态链接版本所得到的有些不一样
\n并且运行时会出现 abort() has been called 的错误
\n(已经修改很多次了还是不行) 😭

$\"code\"$

已经进行试验：使用 ray.cpp 静态链接的话就能得到正确的渲染图

\n","createdAt":"2023-11-07 11:34:23.309987","updatedAt":"2023-11-18 04:57:41.233865","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":102,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":3,"publicVersion":3,"deletedAt":null,"isAnonymous":false,"user":{"id":1081,"username":"KON","name":null,"avatarUrl":"/uploads/image/9f/35/9f3549f065dc7f323da5ebdb5fce01f65bbf19dbd566d5b3d817a08a7b59e7fd.avif","admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":16648,"postNumber":2,"raw":"同学你的代码思路是没问题的，会不会是你的返回值有点问题？","cooked":"

同学你的代码思路是没问题的，会不会是你的返回值有点问题？

\n","createdAt":"2023-11-09 07:03:24.778144","updatedAt":"2023-12-18 09:12:55.830742","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":28,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1488,"username":"roland","name":"李昌洲","avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":16654,"postNumber":3,"raw":"返回值我使用的就是原来的这个\n` return {camera.position, (world_pos - camera.position).normalized()}; `\n\n主要是因为我发现函数 `naive_intersect()` 中 `result.t` 值一直没有更新，渲染的进度条进行的非常快，所以我怀疑是光线的问题，那么就应该是 `naive_intersect()` 这里的问题了，但是我并没有发现错误在哪里 :loudly_crying_face:\n\n![code|690x389](/uploads/image/e2/98/e298c247ce42622e1f92ca1f6ed15d35970a42004f566cb59c1b9c3f7cc910df.avif)\n\n\n在 `trace()` 中给 `naive_intersect()` 传递的参数如下\n![code|690x162](/uploads/image/ec/2f/ec2fe8b8d8eafe7ef0027c3f65b404c471345e428dfdf746b230d55af51a048b.avif)","cooked":"

返回值我使用的就是原来的这个
\nreturn {camera.position, (world_pos - camera.position).normalized()};

主要是因为我发现函数 naive_intersect() 中 result.t 值一直没有更新，渲染的进度条进行的非常快，所以我怀疑是光线的问题，那么就应该是 naive_intersect() 这里的问题了，但是我并没有发现错误在哪里 😭

$\"code\"$

在 trace() 中给 naive_intersect() 传递的参数如下
\n $\"code\"$

\n","createdAt":"2023-11-09 08:06:43.489865","updatedAt":"2023-11-10 06:30:21.684345","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":109,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":3,"publicVersion":3,"deletedAt":null,"isAnonymous":false,"user":{"id":1081,"username":"KON","name":null,"avatarUrl":"/uploads/image/9f/35/9f3549f065dc7f323da5ebdb5fce01f65bbf19dbd566d5b3d817a08a7b59e7fd.avif","admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":16755,"postNumber":4,"raw":"如果一直返回 std::nullopt，说明一直没有相交，那同学你可以检查一下是否发生过任何一次相交。如果一次都没有发生或者只有偶尔几次，说明求解出的光线的方向存在问题。如果发生的次数很正常，那就是在相交后的处理存在问题","cooked":"

如果一直返回 std::nullopt，说明一直没有相交，那同学你可以检查一下是否发生过任何一次相交。如果一次都没有发生或者只有偶尔几次，说明求解出的光线的方向存在问题。如果发生的次数很正常，那就是在相交后的处理存在问题

\n","createdAt":"2023-11-11 03:10:06.936054","updatedAt":"2023-11-11 03:10:06.936054","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":97,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1488,"username":"roland","name":"李昌洲","avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":16759,"postNumber":5,"raw":"这里提供一种检查 `generate_ray` 的方法：\n\n在 Dandelion 中，鼠标点击拾取 (picking) 的操作也是用射线求交实现的，并且也调用了 `generate_ray` 这个函数。因此，你可以借助 *Debug -> Debug Options* 中的 *Show Picking Ray* 这个选项来查看你生成的射线。操作方法是：\n\n1. 启动 Dandelion，从菜单栏上打开 *Debug -> Debug Options -> Show Picking Ray* 这个选项。\n2. 随意点击一次场景中的位置，此时程序会调用 `generate_ray` 生成一条从主视角位置到点击方向的射线。但由于观察位置与射线起点重合，此时看不到射线。\n3. 稍微旋转视角，此时应该会看到一条射线。这条射线应该大致上从刚才所在的位置出发，射向刚刚点击过的位置，可以借助地面方格来辅助观察。\n\n如果你看到了射线，并且看到的射线也符合刚刚观察（点击）的位置，那么 `generate_ray` 应该就没有问题。","cooked":"

这里提供一种检查 generate_ray 的方法：

在 Dandelion 中，鼠标点击拾取 (picking) 的操作也是用射线求交实现的，并且也调用了 generate_ray 这个函数。因此，你可以借助 Debug -> Debug Options 中的 Show Picking Ray 这个选项来查看你生成的射线。操作方法是：

启动 Dandelion，从菜单栏上打开 Debug -> Debug Options -> Show Picking Ray 这个选项。
随意点击一次场景中的位置，此时程序会调用 generate_ray 生成一条从主视角位置到点击方向的射线。但由于观察位置与射线起点重合，此时看不到射线。
稍微旋转视角，此时应该会看到一条射线。这条射线应该大致上从刚才所在的位置出发，射向刚刚点击过的位置，可以借助地面方格来辅助观察。

如果你看到了射线，并且看到的射线也符合刚刚观察（点击）的位置，那么 generate_ray 应该就没有问题。

\n","createdAt":"2023-11-11 04:42:34.099773","updatedAt":"2023-11-11 06:38:36.953998","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":282,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1381,"username":"greyishsong","name":"greyishsong","avatarUrl":"/uploads/image/da/bc/dabc731b0311f59850625bbeb55ed969fcfac0430c5ef0f68441e5466b7aa496.avif","admin":false,"moderator":true,"signatureRaw":null,"signatureCooked":null}},{"id":16823,"postNumber":6,"raw":"我使用助教 @greyishsong 提供的方法，发现 `generate_ray()` 应该是没有问题的。\n但是我在 `naive_intersect()` 中计算得到的 `beta` 和 `gamma` 都不在 0 - 1 之间，**一次相交都没有发生**\n\n![图片|233x500](/uploads/image/f4/e3/f4e358a5d4b27ec895499d398745570f71a82fdaa7c5b958f2b09c68c70b6b08.avif)\n\n传递的参数是 `naive_intersect(ray, object->mesh, object->model())`\n\n在 `naive_intersect()` 中我先进行如下变换\n```c++\nstd::array face = mesh.face(i);\nVector3f a = mesh.vertex(face[0]);\na = (model * Vector4f(a.x(), a.y(), a.z(), 1.0f)).head(3);\n```\n计算过程如下\n```\nVector3f S1 = (ray.direction).cross(c - a);\nVector3f S2 = (ray.origin - a).cross(b - a);\n\nfloat t = S2.dot(c - a) / S1.dot(b - a);\nfloat beta = S1.dot(ray.origin - a) / S1.dot(b - a);\nfloat gamma = S2.dot(ray.direction) / S1.dot(b - a);\n```\n\n请问可能是什么地方的问题呢 :loudly_crying_face:","cooked":"

我使用助教 @greyishsong 提供的方法，发现 generate_ray() 应该是没有问题的。
\n但是我在 naive_intersect() 中计算得到的 beta 和 gamma 都不在 0 - 1 之间，一次相交都没有发生

$\"图片\"$

传递的参数是 naive_intersect(ray, object->mesh, object->model())

在 naive_intersect() 中我先进行如下变换

std::array<size_t, 3> face = mesh.face(i);\nVector3f a = mesh.vertex(face[0]);\na = (model * Vector4f(a.x(), a.y(), a.z(), 1.0f)).head(3);\n

计算过程如下

Vector3f S1 = (ray.direction).cross(c - a);\nVector3f S2 = (ray.origin - a).cross(b - a);\n\nfloat t = S2.dot(c - a) / S1.dot(b - a);\nfloat beta  = S1.dot(ray.origin - a) / S1.dot(b - a);\nfloat gamma = S2.dot(ray.direction) / S1.dot(b - a);\n

请问可能是什么地方的问题呢 😭

\n","createdAt":"2023-11-12 08:36:11.201348","updatedAt":"2023-11-12 08:36:11.201348","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":164,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1081,"username":"KON","name":null,"avatarUrl":"/uploads/image/9f/35/9f3549f065dc7f323da5ebdb5fce01f65bbf19dbd566d5b3d817a08a7b59e7fd.avif","admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":16934,"postNumber":7,"raw":"你的计算过程我推了一下，应该是没问题的。你的实际实现代码里的 T 是 ray.origin-a 吗，如果是的话，那么你目前展示出的代码应该没太大问题，除了返回的法线方向，这个是需要你自己重新计算的，不是直接取这个 mesh 的 normal","cooked":"

你的计算过程我推了一下，应该是没问题的。你的实际实现代码里的 T 是 ray.origin-a 吗，如果是的话，那么你目前展示出的代码应该没太大问题，除了返回的法线方向，这个是需要你自己重新计算的，不是直接取这个 mesh 的 normal

\n","createdAt":"2023-11-13 13:01:14.1617","updatedAt":"2023-11-13 13:01:14.1617","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":94,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1488,"username":"roland","name":"李昌洲","avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":17395,"postNumber":8,"raw":":joy:找到问题了，就是助教 @roland 提到的返回的法线问题，我在修改了之后得到正确结果了，谢谢助教","cooked":"

😂找到问题了，就是助教 @roland 提到的返回的法线问题，我在修改了之后得到正确结果了，谢谢助教

\n","createdAt":"2023-11-18 05:05:19.994597","updatedAt":"2023-11-18 05:05:19.994597","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":42,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1081,"username":"KON","name":null,"avatarUrl":"/uploads/image/9f/35/9f3549f065dc7f323da5ebdb5fce01f65bbf19dbd566d5b3d817a08a7b59e7fd.avif","admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":19998,"postNumber":9,"raw":"同学，你的 ratio 是乘到哪一个向量上的，麻烦能问一下吗","cooked":"

同学，你的 ratio 是乘到哪一个向量上的，麻烦能问一下吗

\n","createdAt":"2023-12-23 07:55:27.408837","updatedAt":"2023-12-23 07:55:27.408837","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":24,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1546,"username":"hahahaha","name":"hahahaha","avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}}],"hasMore":false,"lastReadPostNumber":4,"hasUrlPostNumber":true}