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, 13 insertions, 8 deletions

diff --git a/indra/newview/llviewercontrol.cpp b/indra/newview/llviewercontrol.cpp
index d4d07f24ea..3a6e4e2e2d 100644
--- a/indra/newview/llviewercontrol.cpp
+++ b/indra/newview/llviewercontrol.cpp
@@ -114,32 +114,37 @@ static bool handleRenderAvatarMouselookChanged(const LLSD& newvalue)
 
 static bool handleRenderTextureQualityChanged(const LLSD& newvalue)
 {
-    // 0=Low, 1=Medium, 2=High, 3=Ultra. Drives max-resolution and per-channel
-    // streaming aggressiveness. Channel order is X=normals, Y=diffuse,
-    // Z=specular/metallic, W=emissive (matches TextureChannelPriority).
+    // 0=Low, 1=Medium, 2=High, 3=Ultra. Drives max-resolution and the
+    // per-channel TextureChannelPriority + TextureDistanceDiscardPower
+    // exponents. Channel order: X=normals, Y=diffuse, Z=spec, W=emissive.
     U32 quality = (U32)newvalue.asInteger();
     U32 max_res = 2048;
-    LLVector4 channel_priority(5.f, 7.5f, 20.f, 7.5f);
+    LLVector4 channel_priority(1.f, 0.75f, 0.5f, 0.75f);
+    F32 distance_power = 0.5f;
     switch (quality)
     {
     case 0: // Low
         max_res = 1024;
-        channel_priority.setVec(20.f, 30.f, 80.f, 30.f);
+        channel_priority.setVec(0.5f, 0.75f, 0.1f, 0.5f);
+        distance_power = 0.15f;
         break;
     case 1: // Medium
-        channel_priority.setVec(10.f, 15.f, 40.f, 15.f);
+        channel_priority.setVec(0.75f, 0.75f, 0.3f, 0.75f);
+        distance_power = 0.25f;
         break;
     case 2: // High
-        // defaults above
+        // channel defaults above (1, 0.75, 0.5, 0.75)
+        distance_power = 0.35f;
         break;
     case 3: // Ultra
     default:
-        if (quality > 3) quality = 3;
         channel_priority.setVec(1.f, 1.f, 1.f, 1.f);
+        distance_power = 0.5f;
         break;
     }
     gSavedSettings.setU32("RenderMaxTextureResolution", max_res);
     gSavedSettings.setVector4("TextureChannelPriority", channel_priority);
+    gSavedSettings.setF32("TextureDistanceDiscardPower", distance_power);
     return true;
 }