Lab offers snapshot “tiling” fix

Update: The tiling fixing reached the SL viewer in December 2012, and has subsequently been incorporated into the majority of TPVs. Please refer to your preferred TPv developer for information on the fix (MAINT-628), if unsure.

The ongoing issue with taking high-resolution snapshots resulting in “seams” appearing in captured images may have a final fix on the way.

The issue was initially reported in JIRA MAINT-628 at the end of 2010, and has impacted viewer releases since then, becoming the subject to intense investigation by users and LL alike. The problem has tended to make itself known when taking images at a higher resolution than that of your monitor, resulting in lines breaking-up the captured image, as shown below.

The problem (image courtesy of Dil Spitz)

In reporting the fix, which has a couple of limitations, Runitai gave the following update on the JIRA:

Runitai Linden added a comment – 18/Jul/12 1:57 PM

Fixed in viewer-cat

Fix was to use a large render target for snapshots that are larger than the window, but only when lighting and shadows is enabled. Screen space effects will still show seams when lighting and shadows is disabled.

If the graphics card is unable to allocate a single render target large enough for the high res snapshot, the old method of tiling is still used. On my GTX 580, I could take artifact-free snapshots up to 3500 pixels wide, but could not allocate a full set of render targets at 4000 pixels wide, so the old method is used.

Changes involve an invasive set of changes to LLRenderTarget, so QA should be careful to check various shadow modes, ambient occlusion, depth of field, and anti-aliasing with lighting and shadows enabled. Running with Debug GL enabled will likely cause a crash now when taking high-res snapshots (expected and acceptable behaviour), since the driver reports “out of memory” when trying to allocate a large render target. When Debug GL is not enabled, the viewer handles this error condition gracefully and continues to function.

The code is in a changeset, and will be going through LL’s QA testing. If all goes well, it will hopefully progress through viewer release cycle soon.

2 thoughts on “Lab offers snapshot “tiling” fix

  1. just yesterday I was taking shots and remembered this bug…glad they’re fixing it and am too looking forward to it’s implementation into Firestorm 🙂

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