Rework texture streaming and tracking.

This is a big one:
- Reworks the discard signal almost entirely.  Now has a normalized 0..1 discard signal: distance x size x channel exponent, floored by staleness and background app state.  Shaped by VRAM pressure.
- Textures can now scale down to the smallest GPU mip (1×1), independent of the codec's encoded mip
  count.
- Terrain texture LOD now works.  Useful for 2K textures and PBR on terrain.  Based upon camera distance to nearest terrain patch.
- New texture quality setting.  Low/Medium/High/Ultra
  - Caps texture resolution on Low to 1024, and otherwise shifts the discard signal around.  Makes distance based texture LOD work a lot more predictably.
- We now track last bind state for textures, and discard accordingly.  We progressively discard based upon last bind time.
- Avatar textures get a residency boost to stay loaded in VRAM longer under pressure.

1 files changed, 11 insertions, 1 deletions

diff --git a/indra/newview/lltexturefetch.cpp b/indra/newview/lltexturefetch.cpp
index 51ade60827..574c200eb4 100644
--- a/indra/newview/lltexturefetch.cpp
+++ b/indra/newview/lltexturefetch.cpp
@@ -542,6 +542,7 @@ private:
     S32 mRequestedDiscard;
     S32 mLoadedDiscard;
     S32 mDecodedDiscard;
+    S32 mCodecLevels = 0;
     LLFrameTimer mRequestedDeltaTimer;
     LLFrameTimer mFetchDeltaTimer;
     LLTimer mCacheReadTimer;
@@ -1843,6 +1844,10 @@ bool LLTextureFetchWorker::doWork(S32 param)
             else
             {
                 llassert_always(mRawImage.notNull());
+                if (mFormattedImage.notNull())
+                {
+                    mCodecLevels = (S32)mFormattedImage->getLevels();
+                }
                 LL_DEBUGS(LOG_TXT) << mID << ": Decoded. Discard: " << mDecodedDiscard
                                    << " Raw Image: " << llformat("%dx%d",mRawImage->getWidth(),mRawImage->getHeight()) << LL_ENDL;
                 setState(WRITE_TO_CACHE);
@@ -2774,10 +2779,12 @@ LLTextureFetchWorker* LLTextureFetch::getWorker(const LLUUID& id)
 // Threads:  T*
 bool LLTextureFetch::getRequestFinished(const LLUUID& id, S32& discard_level, S32& worker_state,
                                         LLPointer<LLImageRaw>& raw, LLPointer<LLImageRaw>& aux,
-                                        LLCore::HttpStatus& last_http_get_status)
+                                        LLCore::HttpStatus& last_http_get_status,
+                                        S32& codec_levels)
 {
     LL_PROFILE_ZONE_SCOPED;
     bool res = false;
+    codec_levels = 0;
     LLTextureFetchWorker* worker = getWorker(id);
     if (worker)
     {
@@ -2809,6 +2816,9 @@ bool LLTextureFetch::getRequestFinished(const LLUUID& id, S32& discard_level, S3
             discard_level = worker->mDecodedDiscard;
             raw = worker->mRawImage;
             aux = worker->mAuxImage;
+            // Cached on the worker so the value survives mFormattedImage
+            // clears (cache-retry, decode-abort, write-to-cache complete).
+            codec_levels = worker->mCodecLevels;
 
             decode_time = worker->mDecodeTime;
             fetch_time = worker->mFetchTime;