我可以在像素着色器中生成随机数吗? [英] Can I generate a random number inside a pixel shader?

问题描述

我正在尝试编写一个非常简单的着色器，以向适用对象添加随机闪光.我要执行此操作的方法是在像素着色器内的像素值中添加随机的白色阴影(R = G = B).

I'm trying to write a very simple shader that adds random sparkle to applicable objects. The way I'd like to do this is by adding a random shade of white (R = G = B) to the pixel value within the pixel shader.

似乎noise()不能像我希望的那样工作:

It seems that noise() doesn't work the way I hope it does:

float multiplier = noise(float3(Input.Position[0], Input.Position[1], time));

相对于对noise()的调用，它给我错误X4532:无法将表达式映射到像素着色器指令集".

It gives me "error X4532: cannot map expression to pixel shader instruction set" referring to the call to noise().

由于我不知道在调用着色器之间要保留数字的方法，因此我认为我无法基于渲染前传递的种子编写简单的随机数产生函数.

Since I don't know of a way to retain a number between calls to the shader, I don't think I can just write a simple random number producing function based on a seed passed in before rendering.

是否有一种方法可以从像素着色器内部生成随机数?如果有办法，怎么办?

Is there a way to produce a random number from inside a pixel shader? If there is a way, how?

推荐答案

没有什么可说的，您需要从种子到种子再为运行中的随机生成器重用种子，您只需要任何种子即可.

There's nothing that says you have to reuse the seed for a random generator from run to run, you just need any seed.

例如，如果使用像素坐标，则最终将获得确定性的结果(即像素x，y始终具有相同的随机光斑)，但是总体上将随机分配整个面部.

If you use, say, the pixel coordinate, then you will end up with a deterministic result (i.e. pixel x, y will always have the same random flare to it), but overall the entire face it will be randomly distributed.

现在，如果您输入的内容会根据环境而发生变化(我对像素着色器一无所知)，例如像素在场景/相机组合的全局空间中的整体位置，而不是相对位置.到多边形本身，那么，尤其是在快速移动的环境中，您的结果将有效地随机出现.

Now, if you have available as input something that changes based on the environment (I don't really know anything about pixel shaders), like the overall placement of the pixel in the global space of the scene/camera combination than relative to the polygon itself, then, especially in a fast moving environment, your results will effectively random.

如果全局环境中的所有内容都完全相同，那么，是的，您将具有完全相同的随机"分布.但是，无论这些因素中的任何一个发生变化(特别是基于用户输入，这很可能是您最动态的噪声源")，那么总的效果可能就是足够随机".

If everything in the global environment happens to be exactly the same, then, yes, you will have the exact same "random" distribution. But it any of those factors change (notably based on user input, which it likely you most dynamic "noise source") then overall the effect will be, likely, "random enough".

因此，关键在于，您的种子不必是先前运行随机数生成器的结果.可以是任何东西.因此，根据着色器对您自己的RNG的输入为每个像素构造一个种子，可能会为您带来所需的效果.

So, the key take away is that your seed does not have to be the result of a previous run of the random number generator. It can be anything. So, contriving a seed for each pixel based on inputs to the shader to your own RNG may give you the effect you need.

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