Camera: added function to retrieve size of XY projection plane.

src/SceneGraph/Camera.h

@@ -91,9 +91,20 @@ template<class MatrixType, class VectorType, class ObjectType, class SceneType,
          *
          * Projection matrix handles e.g. perspective distortion and is applied
          * as last.
+         * @see projectionSize()
          */
         inline MatrixType projectionMatrix() const { return _projectionMatrix; }
 
+        /**
+         * @brief Size of (near) XY plane in current projection
+         *
+         * Returns size of near XY plane computed from projection matrix.
+         * @see projectionMatrix()
+         */
+        inline Vector2 projectionSize() const {
+            return {2.0f/rawProjectionMatrix[0].x(), 2.0f/rawProjectionMatrix[1].y()};
+        }
+
         /** @brief Viewport size */
         inline Math::Vector2<GLsizei> viewport() const { return _viewport; }
 

src/SceneGraph/Test/CameraTest.cpp

@@ -75,11 +75,13 @@ void CameraTest::fixAspectRatio() {
 void CameraTest::defaultProjection2D() {
     Camera2D camera;
     CORRADE_COMPARE(camera.projectionMatrix(), Matrix3());
+    CORRADE_COMPARE(camera.projectionSize(), Vector2(2.0f));
 }
 
 void CameraTest::defaultProjection3D() {
     Camera3D camera;
     CORRADE_COMPARE(camera.projectionMatrix(), Matrix4());
+    CORRADE_COMPARE(camera.projectionSize(), Vector2(2.0f));
 }
 
 void CameraTest::projection2D() {
@@ -92,6 +94,7 @@ void CameraTest::projection2D() {
               0.0f,         0.0f,       1.0f);
 
     CORRADE_COMPARE(camera.projectionMatrix(), a);
+    CORRADE_COMPARE(camera.projectionSize(), projectionSize);
 }
 
 void CameraTest::orthographic() {
@@ -105,6 +108,7 @@ void CameraTest::orthographic() {
               0.0f,   0.0f,   -1.25f,     1.0f);
 
     CORRADE_COMPARE(camera.projectionMatrix(), a);
+    CORRADE_COMPARE(camera.projectionSize(), projectionSize);
 
     Vector2 projectionSizeRectangle(5.0f, 4.0f);
     camera.setOrthographic(projectionSizeRectangle, 1, 9);
@@ -115,6 +119,7 @@ void CameraTest::orthographic() {
                       0.0f,   0.0f,   -1.25f,     1.0f);
 
     CORRADE_COMPARE(camera.projectionMatrix(), rectangle);
+    CORRADE_COMPARE(camera.projectionSize(), projectionSizeRectangle);
 }
 
 void CameraTest::perspective() {
@@ -127,6 +132,7 @@ void CameraTest::perspective() {
               0.0f,       0.0f,      -94.1176452f, 0.0f);
 
     CORRADE_COMPARE(camera.projectionMatrix(), a);
+    CORRADE_COMPARE(camera.projectionSize(), Vector2(0.48015756f));
 }
 
 }}}