Customizable camera aspect ratio handling policy.

src/Camera.cpp

@@ -17,6 +17,9 @@
 
 namespace Magnum {
 
+Camera::Camera(AbstractObject* parent): AbstractObject(parent), viewportWidth(0), viewportHeight(0), _aspectRatioPolicy(Extend) {
+}
+
 Matrix4 Camera::cameraMatrix() const {
     /** @todo How to do that? */
     return Matrix4();
@@ -24,6 +27,35 @@ Matrix4 Camera::cameraMatrix() const {
 
 void Camera::setViewport(int width, int height) {
     glViewport(0, 0, width, height);
+
+    viewportWidth = width;
+    viewportHeight = height;
+    fixAspectRatio();
+}
+
+void Camera::fixAspectRatio() {
+    /* Don't divide by zero */
+    if(viewportWidth == 0 || viewportHeight == 0) {
+        _projectionMatrix = rawProjectionMatrix;
+        return;
+    }
+
+    /* Extend on larger side = scale larger side down */
+    if(_aspectRatioPolicy == Extend) {
+        _projectionMatrix = ((viewportWidth > viewportHeight) ?
+            Matrix4::scaling(static_cast<GLfloat>(viewportHeight)/viewportWidth, 1, 1) :
+            Matrix4::scaling(1, static_cast<GLfloat>(viewportWidth)/viewportHeight, 1)
+        )*rawProjectionMatrix;
+
+    /* Clip on smaller side = scale smaller side up */
+    } else if(_aspectRatioPolicy == Clip) {
+        _projectionMatrix = ((viewportWidth > viewportHeight) ?
+            Matrix4::scaling(1, static_cast<GLfloat>(viewportWidth)/viewportHeight, 1) :
+            Matrix4::scaling(static_cast<GLfloat>(viewportHeight)/viewportWidth, 1, 1)
+        )*rawProjectionMatrix;
+
+    /* Don't preserve anything */
+    } else _projectionMatrix = rawProjectionMatrix;
 }
 
 }

src/Camera.h

@@ -30,8 +30,24 @@ namespace Magnum {
  */
 class Camera: public AbstractObject {
     public:
-        /** @copydoc AbstractObject::AbstractObject() */
-        inline Camera(AbstractObject* parent = 0): AbstractObject(parent) {}
+        /** @brief Aspect ratio policy */
+        enum AspectRatioPolicy {
+            NotPreserved,       /**< @brief Don't preserve aspect ratio */
+            Extend,             /**< @brief Extend on larger side of view */
+            Clip                /**< @brief Clip on smaller side of view */
+        };
+
+        /**
+         * @brief Constructor
+         * @param parent        Parent object
+         */
+        Camera(AbstractObject* parent = 0);
+
+        /** @brief Aspect ratio policy */
+        AspectRatioPolicy aspectRatioPolicy() const { return _aspectRatioPolicy; }
+
+        /** @brief Set aspect ratio policy */
+        void setAspectRatioPolicy(AspectRatioPolicy policy) { _aspectRatioPolicy = policy; }
 
         /**
          * @brief Camera matrix
@@ -47,7 +63,7 @@ class Camera: public AbstractObject {
          * Projection matrix handles e.g. perspective distortion and is applied
          * as last.
          */
-        virtual inline Matrix4 projectionMatrix() const { return Matrix4(); }
+        inline Matrix4 projectionMatrix() const { return _projectionMatrix; }
 
         /**
          * @brief Set viewport
@@ -55,10 +71,9 @@ class Camera: public AbstractObject {
          * @param height    Window / buffer height
          *
          * Called when assigning the camera to the scene or when window
-         * size changes. Default implementation preserves aspect ratio and
-         * sets viewport to whole window / buffer size.
+         * size changes.
          */
-        virtual void setViewport(int width, int height);
+        void setViewport(int width, int height);
 
         /**
          * @brief Draw camera
@@ -67,6 +82,15 @@ class Camera: public AbstractObject {
          * nothing.
          */
         virtual void draw(const Magnum::Matrix4& transformationMatrix, const Magnum::Matrix4& projectionMatrix) {}
+
+    private:
+        Matrix4 rawProjectionMatrix;
+        Matrix4 _projectionMatrix;
+
+        int viewportWidth, viewportHeight;
+        AspectRatioPolicy _aspectRatioPolicy;
+
+        void fixAspectRatio();
 };
 
 }