TAA not applying to specific GameObject

I created a volumetric sandstorm in hdrp, but the cost is too high when every pixel is raymarched. So I used compute shader to render a low resolution texture first and then sample that texture on a quad to show the sandstorm. (I am using a quad to show the sandstorm so that the hdrp fog could be applied correctly.)

But I ran into a weird issue. When I am not using compute shader, and raymarch the sandstorm directly on a quad, TAA helps a lot with blurring out some of the artifacts. But when I use the compute shader to calculate a render texture first, TAA does not seem to have any effect. The quads are identical; the algorithm for raymarching the sandstorm is identical; when TAA is turned off, the look of the sandstorms are identical; only when TAA is turned on, the quad without sampling render texture produced by compute shader shows significant improvement on visuals.

I have checked the frame debugger, which is very much the same for these two versions. I didn't spot anything suspicious.

Anyone has any idea what could've caused this? Thanks.

 

So, after some investigation, I suspect the problem comes from the quad not waiting for compute shader to finish rendering the texture. Therefore, the quad is actually still sampling the render texture calculated last frame. And thus there is no difference between current and last frames, which makes TAA not effective.

Anyone knows how to force the material on the quad to wait for compute shader to finish the render texture? Thanks.

 

if you dispatch the compute shader right a t the beginning of the frame it should be ready when it comes to render tansparents. most likely the gpu will not even start rendering until compute has finished.

 

I did some testing and made sure the compute shader actually gets finished first. But TAA is still not effective. So I used mipmap to blur it instead of depending on TAA.

Still quite confused on why TAA is not effective.