initial reverse-z depth implementation

components/sceneutil/util.hpp

@@ -7,6 +7,7 @@
 #include <osg/NodeCallback>
 #include <osg/Texture2D>
 #include <osg/Vec4f>
+#include <osg/Depth>
 
 #include <components/resource/resourcesystem.hpp>
 
@@ -64,6 +65,23 @@ namespace SceneUtil
 
     // Alpha-to-coverage requires a multisampled framebuffer, so we need to set that up for RTTs
     bool attachAlphaToCoverageFriendlyFramebufferToCamera(osg::Camera* camera, osg::Camera::BufferComponent buffer, osg::Texture* texture, unsigned int level = 0, unsigned int face = 0, bool mipMapGeneration = false);
+
+    // Returns a suitable depth state attribute dependent on whether a reverse-z
+    // depth buffer is in use.
+    osg::ref_ptr<osg::Depth> createDepth(bool reverseZ);
+
+    // Returns a perspective projection matrix for use with a reversed z-buffer
+    // and an infinite far plane. This is derived by mapping the default z-range
+    // of [0,1] to [1,0], then taking the limit as far plane approaches
+    // infinity.
+    osg::Matrix getReversedZProjectionMatrixAsPerspectiveInf(double fov, double aspect, double near);
+
+    // Returns a perspective projection matrix for use with a reversed z-buffer.
+    osg::Matrix getReversedZProjectionMatrixAsPerspective(double fov, double aspect, double near, double far);
+
+    // Returns an orthographic projection matrix for use with a reversed z-buffer.
+    osg::Matrix getReversedZProjectionMatrixAsOrtho(double left, double right, double bottom, double top, double near, double far);
+
 }
 
 #endif