DebugTools: render boxes with size as half extent, not full.

Also clarified the documentation in Physics::Box and
Physics::AxisAlignedBox classes.

src/DebugTools/Implementation/AxisAlignedBoxRenderer.cpp

@@ -34,11 +34,9 @@ namespace Magnum { namespace DebugTools { namespace Implementation {
 template<UnsignedInt dimensions> AxisAlignedBoxRenderer<dimensions>::AxisAlignedBoxRenderer(Physics::AxisAlignedBox<dimensions>& axisAlignedBox): axisAlignedBox(axisAlignedBox) {}
 
 template<UnsignedInt dimensions> void AxisAlignedBoxRenderer<dimensions>::draw(Resource<ShapeRendererOptions>& options, const typename DimensionTraits<dimensions>::MatrixType& projectionMatrix) {
-    /* Half scale, because the box is 2x2(x2) */
-    typename DimensionTraits<dimensions>::MatrixType transformation =
+    this->shader->setTransformationProjectionMatrix(projectionMatrix*
         DimensionTraits<dimensions>::MatrixType::translation((axisAlignedBox.transformedMin()+axisAlignedBox.transformedMax())/2)*
-        DimensionTraits<dimensions>::MatrixType::scaling((axisAlignedBox.transformedMax()-axisAlignedBox.transformedMin())/2);
-    this->shader->setTransformationProjectionMatrix(projectionMatrix*transformation)
+        DimensionTraits<dimensions>::MatrixType::scaling(axisAlignedBox.transformedMax()-axisAlignedBox.transformedMin()))
         ->setColor(options->color())
         ->use();
     this->mesh->draw();

src/DebugTools/Implementation/BoxRenderer.cpp

@@ -34,9 +34,7 @@ namespace Magnum { namespace DebugTools { namespace Implementation {
 template<UnsignedInt dimensions> BoxRenderer<dimensions>::BoxRenderer(Physics::Box<dimensions>& box): box(box) {}
 
 template<UnsignedInt dimensions> void BoxRenderer<dimensions>::draw(Resource<ShapeRendererOptions>& options, const typename DimensionTraits<dimensions>::MatrixType& projectionMatrix) {
-    /* Half scale, because the box is 2x2(x2) */
-    this->shader->setTransformationProjectionMatrix(projectionMatrix*box.transformedTransformation()*
-        DimensionTraits<dimensions>::MatrixType::scaling(typename DimensionTraits<dimensions>::VectorType(0.5f)))
+    this->shader->setTransformationProjectionMatrix(projectionMatrix*box.transformedTransformation())
         ->setColor(options->color())
         ->use();
     this->mesh->draw();

src/Physics/AxisAlignedBox.h

@@ -39,6 +39,8 @@ namespace Magnum { namespace Physics {
 /**
 @brief Axis-aligned box
 
+Unit-size means that half extents are equal to 1, equivalent to e.g. sphere
+radius.
 @see AxisAlignedBox2D, AxisAlignedBox3D
 @todo Assert for rotation
 */

src/Physics/Box.h

@@ -39,6 +39,8 @@ namespace Magnum { namespace Physics {
 /**
 @brief Unit-size box with assigned transformation matrix
 
+Unit-size means that half extents are equal to 1, equivalent to e.g. sphere
+radius.
 @todo Use quat + position + size instead?
 @see Box2D, Box3D
 @todo Assert for skew