{"topic":{"id":6608,"title":"渲染部分 vertex_shader","slug":"topic","categoryId":56,"createdAt":"2023-10-21 12:59:01.902254","bumpedAt":"2023-10-23 08:33:50.576355","views":378,"postsCount":6,"highestPostNumber":6,"likeCount":0,"closed":true,"pinned":false,"pinnedGlobally":false,"pinnedAt":null,"pinnedUntil":null,"isBanner":false,"excerpt":"按照文档说明用三角形顶点左乘的 MVP 矩阵得到视角空间的坐标，然后渲染失败了自己 debug 时发现打印变换后的顶点坐标，发现有的 x,y 都大于 1 或小于 -1 了，而且除了 x,y 后面两维度也怪怪的，请问一下大佬们是怎么回事这是输出的乘完 MVP 矩阵后的顶点坐标（不是应该在 -1~1 之间吗？而且看渲染的牛应该在 -0.5~0.5 范围才对）","deletedAt":null,"isAnonymous":false,"category":{"id":56,"name":"计算机图形学","slug":"cg","color":"92278F"},"author":{"id":1547,"username":"R-oh","name":"QQ小孩","avatarUrl":null},"tags":[]},"posts":[{"id":14280,"postNumber":1,"raw":"按照文档说明用三角形顶点左乘的 MVP 矩阵得到视角空间的坐标，\n![屏幕截图 2023-10-21 205104|690x79](/uploads/image/69/86/69864ab68c571fad27e0ab0ab2f9fbeaf9cc316094d99415e135c64a2a79e016.avif)\n\n\n然后渲染失败了\n![屏幕截图 2023-10-21 204728|552x476](/uploads/image/50/85/5085d4e56301d8ce8a23c24c8743bf4310d282a5b8026e669c83818f2d35fae0.avif)\n自己 debug 时发现打印变换后的顶点坐标，发现有的 x,y 都大于 1 或小于 -1 了，而且除了 x,y 后面两维度也怪怪的，请问一下大佬们是怎么回事\n![屏幕截图 2023-10-21 204939|631x227](/uploads/image/b1/70/b170d6dd67146ee44a7d096a65cddae193fc3f7f99438a4cff805f7887f72d70.avif)\n这是输出的乘完 MVP 矩阵后的顶点坐标（不是应该在 -1~1 之间吗？而且看渲染的牛应该在 -0.5~0.5 范围才对）","cooked":"

按照文档说明用三角形顶点左乘的 MVP 矩阵得到视角空间的坐标，
\n $\"屏幕截图$

然后渲染失败了
\n $\"屏幕截图$
\n自己 debug 时发现打印变换后的顶点坐标，发现有的 x,y 都大于 1 或小于 -1 了，而且除了 x,y 后面两维度也怪怪的，请问一下大佬们是怎么回事
\n $\"屏幕截图$
\n这是输出的乘完 MVP 矩阵后的顶点坐标（不是应该在 -1~1 之间吗？而且看渲染的牛应该在 -0.5~0.5 范围才对）

\n","createdAt":"2023-10-21 12:59:01.991718","updatedAt":"2023-10-23 04:45:11.016312","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":158,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":2,"publicVersion":2,"deletedAt":null,"isAnonymous":false,"user":{"id":1547,"username":"R-oh","name":"QQ小孩","avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":14287,"postNumber":2,"raw":"三角形顶点左乘 MVP 矩阵应该还没有到视口空间。\n我自己的理解是，模型坐标系的三角形的顶点坐标左乘 MVP 矩阵后，应当处于一个相机坐标系到 NDC 之间的状态（也就是刚刚做完透视投影）。此时，三角形的顶点坐标（x,y,z）再除以它的第四维 w，就是到了 NDC 空间。\n然后再左乘一个视口变换矩阵，就到了屏幕空间（即 pdf 版文档中的 screen space，好像也称作视口空间）。\n\n当然，我自己也没渲染成功 :loudly_crying_face:，以上也仅供你参考参考。","cooked":"

三角形顶点左乘 MVP 矩阵应该还没有到视口空间。
\n我自己的理解是，模型坐标系的三角形的顶点坐标左乘 MVP 矩阵后，应当处于一个相机坐标系到 NDC 之间的状态（也就是刚刚做完透视投影）。此时，三角形的顶点坐标（x,y,z）再除以它的第四维 w，就是到了 NDC 空间。
\n然后再左乘一个视口变换矩阵，就到了屏幕空间（即 pdf 版文档中的 screen space，好像也称作视口空间）。

当然，我自己也没渲染成功 😭，以上也仅供你参考参考。

\n","createdAt":"2023-10-21 16:13:26.334333","updatedAt":"2023-10-21 16:13:26.334333","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":175,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1508,"username":"tropher","name":null,"avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":14301,"postNumber":3,"raw":"好的，感谢，我去试一试。","cooked":"

好的，感谢，我去试一试。

\n","createdAt":"2023-10-22 04:14:12.715076","updatedAt":"2023-10-22 04:14:12.715076","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":12,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1547,"username":"R-oh","name":"QQ小孩","avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":14345,"postNumber":4,"raw":"@tropher 这个同学的理解是正确的，到了 NDC 空间后，可视区域每一维的坐标都是 -1 到 1(超出的部分会在 rasterization 中被剔除)，变换到视口空间只需将 x.y 变换到对应的长宽，z 则变换到 0 到某个特定的值。这时才能算作变换到视口空间","cooked":"

@tropher 这个同学的理解是正确的，到了 NDC 空间后，可视区域每一维的坐标都是 -1 到 1(超出的部分会在 rasterization 中被剔除)，变换到视口空间只需将 x.y 变换到对应的长宽，z 则变换到 0 到某个特定的值。这时才能算作变换到视口空间

\n","createdAt":"2023-10-23 03:14:54.782589","updatedAt":"2023-10-23 04:50:01.239564","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":14350,"postNumber":5,"raw":"你修改了 MVP 矩阵吗？或者你在把 newtriangle.vertex[i] 写入 payload 传给 vertex_shader 前修改过 newtriangle.vertex 吗？我都没修改，乘了 MVP 矩阵之后 xy 范围是对的\n![Screenshot from 2023-10-23 13-06-25|690x329](/uploads/image/5d/6a/5d6a10e9cd698b55bdc136d4d7a99e09fd877003d66e18797ec97277e479c1f5.avif)","cooked":"

你修改了 MVP 矩阵吗？或者你在把 newtriangle.vertex[i] 写入 payload 传给 vertex_shader 前修改过 newtriangle.vertex 吗？我都没修改，乘了 MVP 矩阵之后 xy 范围是对的
\n $\"Screenshot$

\n","createdAt":"2023-10-23 05:10:33.312727","updatedAt":"2023-10-23 05:10:33.312727","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":51,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1525,"username":"222333","name":"Hadeon","avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}},{"id":14360,"postNumber":6,"raw":"@222333 没有动 MVP 矩阵，传的顶点就是三角形的模型坐标系的顶点也没有动，乘完就是我帖子那样 :loudly_crying_face:，但是按照上面这位同学说的做了后好了。","cooked":"

@222333 没有动 MVP 矩阵，传的顶点就是三角形的模型坐标系的顶点也没有动，乘完就是我帖子那样 😭，但是按照上面这位同学说的做了后好了。

\n","createdAt":"2023-10-23 08:33:50.576355","updatedAt":"2023-10-23 08:33:50.576355","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":59,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1547,"username":"R-oh","name":"QQ小孩","avatarUrl":null,"admin":false,"moderator":false,"signatureRaw":null,"signatureCooked":null}}],"hasMore":false,"lastReadPostNumber":6,"hasUrlPostNumber":true}