Caching light position relative to camera.

Saves one matrix*vector multiplication per object per frame. The
position can be now Vector3 like before, because it won't be multiplied
with anything on draw call. Added unit test.

src/CMakeLists.txt

@@ -42,6 +42,15 @@ install(TARGETS Magnum DESTINATION ${MAGNUM_LIBRARY_INSTALL_DIR})
 
 if(BUILD_TESTS)
     enable_testing()
+
+    # Library with graceful assert for testing
+    add_library(MagnumTestLib SHARED ${Magnum_SRCS})
+    if(WIN32)
+        set_target_properties(MagnumTestLib PROPERTIES COMPILE_FLAGS -DMAGNUM_EXPORTING)
+    endif()
+    set_target_properties(MagnumTestLib PROPERTIES COMPILE_FLAGS -DCORRADE_GRACEFUL_ASSERT)
+    target_link_libraries(MagnumTestLib ${CORRADE_UTILITY_LIBRARY} ${CORRADE_PLUGINMANAGER_LIBRARY} ${OPENGL_gl_LIBRARY} ${GLEW_LIBRARY})
+
     include_directories(${QT_INCLUDE_DIR})
     add_subdirectory(Test)
 endif()

src/Light.cpp

@@ -14,12 +14,25 @@
 */
 
 #include "Light.h"
+#include "Camera.h"
 
 namespace Magnum {
 
+Vector3 Light::position(Camera* camera) {
+    CORRADE_ASSERT(scene() && camera->scene() == scene(), "Light: camera and light aren't in the same scene!", Vector3())
+
+    if(camera != _camera) {
+        _camera = camera;
+        setDirty();
+    }
+
+    setClean();
+    return _position;
+}
+
 void Light::setClean() {
     if(!isDirty()) return;
-    _position = absoluteTransformation()[3];
+    _position = (absoluteTransformation()*_camera->cameraMatrix())[3].xyz();
     Object::setClean();
 }
 

src/Light.h

@@ -34,15 +34,15 @@ class Light: public Object {
          * @brief Constructor
          * @param parent        Parent object
          */
-        inline Light(Object* parent = nullptr): Object(parent) {}
+        inline Light(Object* parent = nullptr): Object(parent), _camera(nullptr) {}
 
         /**
-         * @brief Light position relative to root object (scene)
+         * @brief Light position relative to given camera
+         *
+         * The position is cached until the camera is changed to another or
+         * the light dirty bit is set.
          */
-        inline Vector4 position() {
-            setClean();
-            return _position;
-        }
+        Vector3 position(Camera* camera);
 
         /**
          * Recomputes light position.
@@ -50,7 +50,8 @@ class Light: public Object {
         void setClean();
 
     private:
-        Vector4 _position;
+        Camera* _camera;
+        Vector3 _position;
 };
 
 }

src/Test/CMakeLists.txt

@@ -1,3 +1,4 @@
 corrade_add_test(ObjectTest ObjectTest.h ObjectTest.cpp Magnum)
 corrade_add_test(CameraTest CameraTest.h CameraTest.cpp Magnum)
+corrade_add_test(LightTest LightTest.h LightTest.cpp MagnumTestLib)
 corrade_add_test(SceneTest SceneTest.h SceneTest.cpp Magnum)

src/Test/LightTest.cpp

@@ -0,0 +1,63 @@
+/*
+    Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz>
+
+    This file is part of Magnum.
+
+    Magnum is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License version 3
+    only, as published by the Free Software Foundation.
+
+    Magnum is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU Lesser General Public License version 3 for more details.
+*/
+
+#include "LightTest.h"
+
+#include <sstream>
+#include <QtTest/QTest>
+
+#include "Camera.h"
+#include "Light.h"
+#include "Scene.h"
+
+QTEST_APPLESS_MAIN(Magnum::Test::LightTest)
+
+using namespace std;
+using namespace Corrade::Utility;
+
+namespace Magnum { namespace Test {
+
+void LightTest::positionWrongCamera() {
+    stringstream ss;
+    Error::setOutput(&ss);
+
+    Camera c;
+    Light l;
+    QVERIFY(l.position(&c) == Vector3());
+    QVERIFY(ss.str() == "Light: camera and light aren't in the same scene!\n");
+}
+
+void LightTest::position() {
+    Scene s;
+
+    Object lightParent(&s);
+    lightParent.translate(Vector3::zAxis(3));
+    Light light(&lightParent);
+
+    Object cameraParent(&s);
+    cameraParent.rotate(deg(90.0f), Vector3::xAxis());
+    Camera camera(&cameraParent);
+
+    QVERIFY(light.position(&camera) == (Matrix4::translation(Vector3::zAxis(3))*
+        Matrix4::rotation(deg(90.0f), Vector3::xAxis()).inversed())[3].xyz());
+
+    /* Set another camera */
+    Camera another(&cameraParent);
+    another.scale(Vector3(3.0f));
+    QVERIFY(light.position(&another) == (Matrix4::translation(Vector3::zAxis(3))*
+        (Matrix4::scaling(Vector3(3.0f))*Matrix4::rotation(deg(90.0f), Vector3::xAxis())).inversed())[3].xyz());
+}
+
+}}

src/Test/LightTest.h

@@ -0,0 +1,32 @@
+#ifndef Magnum_Test_LightTest_h
+#define Magnum_Test_LightTest_h
+/*
+    Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz>
+
+    This file is part of Magnum.
+
+    Magnum is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License version 3
+    only, as published by the Free Software Foundation.
+
+    Magnum is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU Lesser General Public License version 3 for more details.
+*/
+
+#include <QtCore/QObject>
+
+namespace Magnum { namespace Test {
+
+class LightTest: public QObject {
+    Q_OBJECT
+
+    private slots:
+        void positionWrongCamera();
+        void position();
+};
+
+}}
+
+#endif