DebugTools: properly implemented special cases for CapsuleRenderer.

src/DebugTools/Implementation/CapsuleRendererTransformation.h

@@ -26,6 +26,7 @@
 
 #include <array>
 
+#include "Math/Functions.h"
 #include "Math/Matrix3.h"
 #include "Math/Matrix4.h"
 #include "Magnum.h"
@@ -72,10 +73,21 @@ template<> std::array<Matrix4, 3> capsuleRendererTransformation<3>(const Vector3
     Vector3 capDistance;
     if(length >= Math::TypeTraits<Float>::epsilon()) {
         const Vector3 directionNormalized = direction/length;
-        rotation.up() = directionNormalized;
-        rotation.right() = Vector3::cross(rotation.up(), Vector3::zAxis()).normalized();
-        rotation.backward() = Vector3::cross(rotation.right(), rotation.up());
-        CORRADE_INTERNAL_ASSERT(rotation.up().isNormalized() && rotation.backward().isNormalized());
+        const Float dot = Vector3::dot(directionNormalized, Vector3::zAxis());
+
+        /* Direction is parallel to Z axis, special rotation case */
+        if(Math::abs(dot) > 1.0f - Math::TypeTraits<Float>::epsilon()) {
+            rotation.up() = dot*Vector3::zAxis();
+            rotation.right() = Vector3::xAxis();
+            rotation.backward() = -dot*Vector3::yAxis();
+
+        /* Common case */
+        } else {
+            rotation.up() = directionNormalized;
+            rotation.right() = Vector3::cross(rotation.up(), Vector3::zAxis()).normalized();
+            rotation.backward() = Vector3::cross(rotation.right(), rotation.up());
+            CORRADE_INTERNAL_ASSERT(rotation.up().isNormalized() && rotation.backward().isNormalized());
+        }
 
         capDistance = directionNormalized*radius;
     }

src/DebugTools/Test/CapsuleRendererTest.cpp

@@ -36,6 +36,8 @@ class CapsuleRendererTest: public TestSuite::Tester {
         void common2D();
 
         void zeroLength3D();
+        void parallel3D();
+        void antiParallel3D();
         void common3D();
 };
 
@@ -44,6 +46,8 @@ CapsuleRendererTest::CapsuleRendererTest() {
               &CapsuleRendererTest::common2D,
 
               &CapsuleRendererTest::zeroLength3D,
+              &CapsuleRendererTest::parallel3D,
+              &CapsuleRendererTest::antiParallel3D,
               &CapsuleRendererTest::common3D});
 }
 
@@ -100,6 +104,42 @@ void CapsuleRendererTest::zeroLength3D() {
     CORRADE_COMPARE(transformation[2].translation(), a);
 }
 
+void CapsuleRendererTest::parallel3D() {
+    const Vector3 a(0.5f, 3.0f, 7.0f);
+    const Vector3 b(0.5f, 3.0f, 11.0f);
+    std::array<Matrix4, 3> transformation = Implementation::capsuleRendererTransformation<3>(a, b, 3.5f);
+
+    const auto rotation = Matrix4::rotationX(Deg(90.0f));
+    const auto scaling = (rotation*Matrix4::scaling(Vector3(3.5f))).rotationScaling();
+    CORRADE_COMPARE(transformation[0].rotationScaling(), scaling);
+    CORRADE_COMPARE(transformation[1].rotationScaling(),
+        (rotation*Matrix4::scaling({3.5f, 2.0f, 3.5f})).rotationScaling());
+    CORRADE_COMPARE(transformation[2].rotationScaling(), scaling);
+
+    const auto capDistance = Vector3::zAxis(3.5f);
+    CORRADE_COMPARE(transformation[0].translation(), a+capDistance);
+    CORRADE_COMPARE(transformation[1].translation(), a+Vector3::zAxis(2.0f));
+    CORRADE_COMPARE(transformation[2].translation(), b-capDistance);
+}
+
+void CapsuleRendererTest::antiParallel3D() {
+    const Vector3 a(0.5f, 3.0f, 7.0f);
+    const Vector3 b(0.5f, 3.0f, 3.0f);
+    std::array<Matrix4, 3> transformation = Implementation::capsuleRendererTransformation<3>(a, b, 3.5f);
+
+    const auto rotation = Matrix4::rotationX(-Deg(90.0f));
+    const auto rotationScaling = (rotation*Matrix4::scaling(Vector3(3.5f))).rotationScaling();
+    CORRADE_COMPARE(transformation[0].rotationScaling(), rotationScaling);
+    CORRADE_COMPARE(transformation[1].rotationScaling(),
+        (rotation*Matrix4::scaling({3.5f, 2.0f, 3.5f})).rotationScaling());
+    CORRADE_COMPARE(transformation[2].rotationScaling(), rotationScaling);
+
+    const auto capDistance = Vector3::zAxis(-3.5f);
+    CORRADE_COMPARE(transformation[0].translation(), a+capDistance);
+    CORRADE_COMPARE(transformation[1].translation(), a+Vector3::zAxis(-2.0f));
+    CORRADE_COMPARE(transformation[2].translation(), b-capDistance);
+}
+
 void CapsuleRendererTest::common3D() {
     const Vector3 a(0.5f, 3.0f, 7.0f);
     const Vector3 b(7.5f, -1.0f, 1.5f);