From e66fd1dc709a0409081861ae43a2bc61f9e9e45a Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Wed, 26 Oct 2005 20:00:10 +0000
Subject: [PATCH] Changed the minimum tile image size to be 4x4 to avoid
 problems in mipmap generation that was occuring at sizes of 2x2, seemingly
 somewhere in the OpenGL driver.

---
 src/osgTerrain/DataSet.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/osgTerrain/DataSet.cpp b/src/osgTerrain/DataSet.cpp
index 1575a81f7..5684723ce 100644
--- a/src/osgTerrain/DataSet.cpp
+++ b/src/osgTerrain/DataSet.cpp
@@ -1451,8 +1451,10 @@ bool DataSet::DestinationTile::computeImageResolution(unsigned int layer, unsign
         unsigned int numColumnsRequired = osg::minimum(_imagery_maxNumColumns,numColumnsAtFullRes);
         unsigned int numRowsRequired    = osg::minimum(_imagery_maxNumRows,numRowsAtFullRes);
 
-        numColumns = 1;
-        numRows = 1;
+        // use a minimum image size of 4x4 to avoid mipmap generation problems in OpenGL at sizes at 2x2. 
+        numColumns = 4;
+        numRows = 4;
+        
         // round to nearest power of two above or equal to the required resolution
         while (numColumns<numColumnsRequired) numColumns *= 2;
         while (numRows<numRowsRequired) numRows *= 2;
@@ -2246,7 +2248,7 @@ osg::StateSet* DataSet::DestinationTile::createStateSet()
 
         bool inlineImageFile = _dataSet->getDestinationTileExtension()==".ive";
         bool compressedImageSupported = inlineImageFile || imageExension==".dds";
-        bool mipmapImageSupported = inlineImageFile;
+        bool mipmapImageSupported = compressedImageSupported; // inlineImageFile;
         
         int minumCompressedTextureSize = 64;
         int minumDXT3CompressedTextureSize = 256;