Experimental fix for blurry textures (#1875)

This change removes the distance based bias (which is a large contributor to premature blurring) but adds a check using the importance factor to give some balance.
importance should be between 0 and 1 and is higher when the texture is facing the camera, lower when it is side on,
The unimportance setting defines the cutoff vaklue below which we'll consider the textures worth "down scaling" by the bias factor. The setting is inplace to allow us to play with this, 0.25 is current default.

Note this change moves the calcPixelArea() call to the top BEFORE we user getPixelArea(). Either that call is entirely redundant (i.e. if calc was called earlier in the frame)  or we were using the stale pixelArea (one frame behind). If the former is true then it might be faster to just do an AABB frustum check.

2 files changed, 18 insertions, 7 deletions

diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index c455b6f5f1..e56facd615 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -11289,6 +11289,19 @@
       <key>Value</key>
       <real>8.0</real>
     </map>
+    <key>TextureBiasUnimportantFactor</key>
+    <map>
+      <key>Comment</key>
+      <string>When biasing textures to lower resolution due to lack of vram, the importance threshold below which is considered unimportant and getting an extra bias.</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>F32</string>
+      <key>Value</key>
+      <real>0.25</real>
+      <key>Backup</key>
+      <integer>0</integer>
+    </map>
     <key>TextureDecodeDisabled</key>
     <map>
       <key>Comment</key>
diff --git a/indra/newview/llviewertexturelist.cpp b/indra/newview/llviewertexturelist.cpp
index 4d8fd8ddd5..2f685474e1 100644
--- a/indra/newview/llviewertexturelist.cpp
+++ b/indra/newview/llviewertexturelist.cpp
@@ -931,6 +931,10 @@ void LLViewerTextureList::updateImageDecodePriority(LLViewerFetchedTexture* imag
 
                 if (face && face->getViewerObject() && face->getTextureEntry())
                 {
+                    F32 radius;
+                    F32 cos_angle_to_view_dir;
+                    BOOL in_frustum = face->calcPixelArea(cos_angle_to_view_dir, radius);
+                    static LLCachedControl<F32> bias_unimportant_threshold(gSavedSettings, "TextureBiasUnimportantFactor", 0.25f);
                     F32 vsize = face->getPixelArea();
 
                     // Scale desired texture resolution higher or lower depending on texture scale
@@ -944,13 +948,7 @@ void LLViewerTextureList::updateImageDecodePriority(LLViewerFetchedTexture* imag
                     min_scale = llclamp(min_scale*min_scale, texture_scale_min(), texture_scale_max());
 
                     vsize /= min_scale;
-                    vsize /= LLViewerTexture::sDesiredDiscardBias;
-                    vsize /= llmax(1.f, (LLViewerTexture::sDesiredDiscardBias-1.f) * (1.f + face->getDrawable()->mDistanceWRTCamera * bias_distance_scale));
-
-                    F32 radius;
-                    F32 cos_angle_to_view_dir;
-                    bool in_frustum = face->calcPixelArea(cos_angle_to_view_dir, radius);
-                    if (!in_frustum || !face->getDrawable()->isVisible())
+                    if (!in_frustum || !face->getDrawable()->isVisible() || face->getImportanceToCamera() < bias_unimportant_threshold)
                     { // further reduce by discard bias when off screen or occluded
                         vsize /= LLViewerTexture::sDesiredDiscardBias;
                     }