Is there a way to concurrently write to a UAV without race condition?

Question

I have a compute shader which simulates some fluid as particle. Particles are read from a buffer. Each particle is handled in one thread. During the execution of the thread, one particle moves its uv position and adds to pixel of a UAV named Water . Therefore each thread leaves a trail of its movement on the Water texture.

_watTx[texID] += watAddition * cellArea.x;

The problem is there are lots of particles moving around and most often multiples are present at the same texID. It seems there is a race condition since every time I run the simulation the results are slightly different. Is there a way to enforce mutual exclusion so the writes do not happen at the same time and the results become predictable?

Answer 1

我找到了解决此问题的方法。 InterlockedAdd以原子方式添加到像素。但它仅适用于int和unit无人机。

在我的情况下，值是浮点值，但范围非常有限（如0到10）。所以解决方案是使用int无人机。我们将计算结果乘以一个巨大的数字（如10000），然后写入无人机：

InterlockedAdd(_watTx[texID], (watAddition * cellArea.x * 10000));

结果的精度为0.0001，在我的情况下完全没问题。在另一个像素或计算着色器中，我们可以将int UAV中的值乘以0.0001并写入所需的浮点渲染目标。

此过程消除了并发写入问题，并且每次运行的结果都相同。