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opengL：glsl着色器中的镜像对象

[英]opengL: mirror object in glsl shader

原文 2011-03-21 23:30:53 1 1 opengl/ 3d/ glsl

is it possible to mirror an object along some axis, just in the vertex shader? 是否可以沿着某个轴镜像对象，只是在顶点着色器中？

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. 如果我只是在投影矩阵中将一个轴缩放-1，我会得到不好的剔除，并且需要在应用程序中将剔除从背面更改为前面。 is there a way to do it without changing the culling? 有没有办法在不改变剔除的情况下做到这一点？

thanks! 谢谢！

1 个解决方案

Culling is done based on the so called chirality of the face, ie the turning direction in which the vertices are drawn. 基于所谓的面部手征（即，绘制顶点的转动方向）来完成剔除。 It is the core property of a reflection that it changes the chirality. 反射的核心属性是它改变了手性。 So you'll inevitably have to switch the culling behaviour, since back-/frontface culling happens purely on the chirality in screen space. 所以你不可避免地要切换剔除行为，因为背面/正面剔除完全取决于屏幕空间中的手性。

You could use a geometry shader to exchange two vertices of each triangle which will also switch the chirality. 您可以使用几何着色器来交换每个三角形的两个顶点，这也将切换手性。 But frankly: Reflections require some additional precautions like stencil masking and such; 但坦率地说：反思需要一些额外的预防措施，如模板掩模等; switching the culling function is no big deal then, too. 切换剔除功能也没什么大不了的。