opengL：glsl 着色器中的镜像对象
是否可以仅在顶点着色器中沿某个轴镜像对象？
如果我只是将投影矩阵中的一个轴缩放 -1，则会得到糟糕的剔除效果，并且需要在应用程序中将剔除从背面更改为正面。有没有办法在不改变剔除的情况下做到这一点？
谢谢！
is it possible to mirror an object along some axis, just in the vertex shader?
if i simply scale one axis by -1 in the projection matrix, i get bad culling and would need to change the culling from backface to frontface in the application. is there a way to do it without changing the culling?
thanks!
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剔除是基于所谓的面的手性（即绘制顶点的旋转方向）来完成的。反射的核心属性是改变手性。因此，您将不可避免地必须切换剔除行为，因为背面/正面剔除纯粹发生在屏幕空间中的手性上。
您可以使用几何着色器来交换每个三角形的两个顶点，这也会切换手性。但坦率地说：反射需要一些额外的预防措施，例如模板遮蔽等；那么切换剔除功能也没什么大不了的。
Culling is done based on the so called chirality of the face, i.e. the turning direction in which the vertices are drawn. It is the core property of a reflection that it changes the chirality. So you'll inevitably have to switch the culling behaviour, since back-/frontface culling happens purely on the chirality in screen space.
You could use a geometry shader to exchange two vertices of each triangle which will also switch the chirality. But frankly: Reflections require some additional precautions like stencil masking and such; switching the culling function is no big deal then, too.