Nsight shows made-up mipmaps for 2D array images.

Developer Tools Nsight Visual Studio Edition
1

Version 5.5.0.18014

Took me a while to realize that NSight is lying about the mipmap contents. Was puzzled by a weird mipmaping glitch as everything looked correct at NSight side.

Specifically NSight shows his own auto-generated mipmaps for VK_FORMAT_BC3_UNORM_BLOCK 2D array images - and NOT what they actually contain.

Correct behavior: either do not show mipmaps at all or show their actual content.

Is this a known bug? Is it fixed in latest release?

2

Hi tanzanite7,

Do you have a sample app that can reproduce this issue?
Can you share it with us?
Thanks!

3

While the problem is 100% reproducible, the app is not shareable at this time (too many internal dependencies). I have looked around to find some simple vulkan wrapper for this kind of purposes (something to make simple/rigid minimal test programs) - but have not found any. If you can point to any … might come handy later anyway (*).

What i can say for sure:

  • whatever i upload is exactly what is used to render (ex: if i upload pure white image with all mipmaps being pure red - then that is what i get it rendered as)
  • Nsight shows only the base image correctly and all the actual mipmaps are ignored and downsampled versions of base image get shown instead.

Image:

  • 1024x1024 8-layer image: VK_FORMAT_BC3_UNORM_BLOCK
  • allocated with dedicated memory (vkExtDedicatedAllocNV)
  • only 2 layers uploaded, the 0th being with unmistakably wrong mipmaps (ex: white image with all its mimpams being red - which NSight will show as also being pure white [or whatever the base image would downsample into])

*) Off Topic: Currently there are some code changes underway and can not test much, but i recon i am gonna need something as i have encountered what seems to be an unrelated driver bug:

Current nvidia drivers seem to ignore or fail to adhere to “invariant” decoration in SPIR-V. At least no-one has come up with any other explanation.

Probably going to need something to make a repro app when i get back to it.

4

Hi tanzanite7,

We have reproduced the issue, and have created an internal case to track it. We’ll let you know if there’s any update about it. Thanks!

5

Hi tanzanite7,

This issue has been confirmed fixed. Please take a try on the next release version of Nsight Graphics.