Add mapnode option overlay_blending_source with default value 'alpha'…

…, legal value 'color', to change the behavior of imageoverlay/draping blending function.
gwaldron · May 16, 2023 · 6fc9f66 · 6fc9f66
1 parent bae98fe
commit 6fc9f66
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Showing 5 changed files with 37 additions and 2 deletions.
diff --git a/src/osgEarth/DrapingTechnique b/src/osgEarth/DrapingTechnique
@@ -86,6 +86,12 @@ namespace osgEarth { namespace Util
         void setOverlayBlending( bool value );
         bool getOverlayBlending() const { return _rttBlending; }
 
+        /**
+        * Set the blending function sources to use when overlay blending is true.
+        * Defaults are GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA
+        */
+        void setOverlayBlendingParams(GLenum src, GLenum dst);
+
         /**
          * Whether to attach the RTT to camera to the stencil buffer.  Default = false.
          * Some older cards don't have very good support 
@@ -133,6 +139,8 @@ namespace osgEarth { namespace Util
         bool                          _rttBlending;
         bool                          _attachStencil;
         double                        _maxFarNearRatio;
+        GLenum _overlaySource = GL_SRC_ALPHA;
+        GLenum _overlayDestination = GL_ONE_MINUS_SRC_ALPHA;
 
         mutable std::shared_ptr<DrapingManager> _drapingManager;
         std::shared_ptr<DrapingManager>& getDrapingManager() { return _drapingManager; }

diff --git a/src/osgEarth/DrapingTechnique.cpp b/src/osgEarth/DrapingTechnique.cpp
@@ -507,11 +507,11 @@ DrapingTechnique::setUpCamera(OverlayDecorator::TechRTTParams& params)
         if (Registry::capabilities().supportsGLSL(140u))
         {
             //Blend Func Separate is only available on OpenGL 1.4 and above
-            blendFunc = new osg::BlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_COLOR, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+            blendFunc = new osg::BlendFunc(_overlaySource, _overlayDestination, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
         }
         else
         {
-            blendFunc = new osg::BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+            blendFunc = new osg::BlendFunc(_overlaySource, _overlayDestination);
         }
 
         rttStateSet->setAttributeAndModes(blendFunc, osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
@@ -714,6 +714,13 @@ DrapingTechnique::setOverlayBlending( bool value )
     }
 }
 
+void
+DrapingTechnique::setOverlayBlendingParams(GLenum src, GLenum dst)
+{
+    _overlaySource = src;
+    _overlayDestination = dst;
+}
+
 bool
 DrapingTechnique::getAttachStencil() const
 {

diff --git a/src/osgEarth/MapNode b/src/osgEarth/MapNode
@@ -66,6 +66,7 @@ namespace osgEarth
             OE_OPTION(ProxySettings, proxySettings);
             OE_OPTION(bool, enableLighting);
             OE_OPTION(bool, overlayBlending);
+            OE_OPTION(bool, overlayBlendingSource);
             OE_OPTION(unsigned, overlayTextureSize);
             OE_OPTION(bool, overlayMipMapping);
             OE_OPTION(float, overlayResolutionRatio);

diff --git a/src/osgEarth/MapNode.cpp b/src/osgEarth/MapNode.cpp
@@ -196,6 +196,7 @@ MapNode::Options::getConfig() const
     conf.set( "proxy",                    proxySettings() );
     conf.set( "lighting",                 enableLighting() );
     conf.set( "overlay_blending",         overlayBlending() );
+    conf.set( "overlay_blending_source",  overlayBlendingSource());
     conf.set( "overlay_texture_size",     overlayTextureSize() );
     conf.set( "overlay_mipmapping",       overlayMipMapping() );
     conf.set( "overlay_resolution_ratio", overlayResolutionRatio() );
@@ -215,6 +216,7 @@ MapNode::Options::fromConfig(const Config& conf)
     proxySettings().init(ProxySettings());
     enableLighting().init(true);
     overlayBlending().init(true);
+    overlayBlendingSource().init("alpha");
     overlayMipMapping().init(false);
     overlayTextureSize().init(4096);
     overlayResolutionRatio().init(3.0f);
@@ -226,6 +228,7 @@ MapNode::Options::fromConfig(const Config& conf)
     conf.get( "proxy",                    proxySettings() );
     conf.get( "lighting",                 enableLighting() );
     conf.get( "overlay_blending",         overlayBlending() );
+    conf.get( "overlay_blending_source",  overlayBlendingSource());
     conf.get( "overlay_texture_size",     overlayTextureSize() );
     conf.get( "overlay_mipmapping",       overlayMipMapping() );
     conf.get( "overlay_resolution_ratio", overlayResolutionRatio() );
@@ -391,6 +394,11 @@ MapNode::open()
         if ( options().overlayBlending().isSet() )
             draping->setOverlayBlending( options().overlayBlending().get() );
 
+        if (options().overlayBlendingSource().isSetTo("color"))
+            draping->setOverlayBlendingParams(GL_SRC_COLOR, GL_ONE_MINUS_SRC_COLOR);
+        else if (options().overlayBlendingSource().isSetTo("alpha"))
+            draping->setOverlayBlendingParams(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
         if ( envOverlayTextureSize )
             draping->setTextureSize( as<int>(envOverlayTextureSize, 1024) );
 

diff --git a/tests/annotation.earth b/tests/annotation.earth
@@ -3,6 +3,10 @@ osgEarth Sample - Annotations
 -->
 <map name="Annotations Demo">
 
+    <options>
+        <overlay_blending_source>alpha</overlay_blending_source>
+    </options>
+
     <xi:include href="readymap_imagery.xml"/>
     <xi:include href="readymap_elevation.xml"/>
 
@@ -183,6 +187,13 @@ osgEarth Sample - Annotations
         </imageoverlay>
         <label text="ImageOverlay" lat="26" long="-81"/>
 
+        <imageoverlay>
+            <url>../data/fractal.png</url>
+            <alpha>0.75</alpha>
+            <geometry>POLYGON((-81 28, -80.5 28, -80.5 28.5, -81 28.5))</geometry>
+        </imageoverlay>
+        <label text="ImageOverlay(alpha)" lat="28" long="-81"/>
+
         <local_geometry name="3D geometry">
             <geometry>
                 POLYGON((0 0 0, -25000 0 45000, 0 0 75000, 25000 0 45000))