glsl&变化值的透视校正 [英] glsl & perspective correction of varying values

问题描述

光栅化器是否使用透视校正对每个变化的顶点值(或在超出"顶点着色器的glsl值的较新版本中)进行插值?这个硬件依赖吗?

is every varying vertex value (or in newer versions of glsl values that go "out" of a vertex shader) interpolated by the rasterizer using perspective correction? is this hardware dependant?

发生剪切时，如何计算剪切顶点处的值?

when clipping occurs, how are the values at the clipping vertices calculated?

我尝试撤消透视校正，并注意剪切后的多边形的奇怪行为，我想更好地了解幕后情况.

I try to undo perspective correction and notice strange behaviour for polygons that are clipped and I would like to understand better what is going on behind the scenes.

推荐答案

Pre-GL 3.0，影响透视正确插值的唯一方法是使用提示.通常，glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST)将激活所有变化的透视校正插值，而glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST)通常将其关闭.请注意，这些只是驱动程序提示，仅此而已；驾驶员没有没有以这种方式做出反应.

Pre-GL 3.0, the only way to affect perspective-correct interpolation is with a hint. Generally, glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST) will activate perspective-correct interpolation on all varyings, while glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST) will generally turn it off. Note that these are driver hints and nothing more; drivers don't have to react this way.

在GLSL 1.30+(OpenGL 3.0+)中，您可以强制以特定方式对每个输出/输入进行插值. 插值限定符 smooth表示透视正确；如果您未指定限定符，则为默认设置. noperspective意味着...显而易见.

In GLSL 1.30+ (OpenGL 3.0+), you have the ability to force each output/input to interpolate in a specific way. The interpolation qualifier smooth means perspective-correct; this is the default if you don't specify a qualifier. noperspective means... the obvious.

剪辑总是以某种方式进行，就像它没有被剪辑(或在硬件精度范围内足够接近)一样.因此，如果正确地对某个值进行透视插值，则为裁剪后的顶点生成的值也必须使用透视正确的插值.

Clipping is always done in such a way that it will work exactly as if it weren't clipped (or near enough within hardware precision). So if a value is interpolated perspective-correctly, then the value generated for the clipped vertex must also use perspective-correct interpolation.

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