Merge pull request #14 from Patch2PDF/rotation-fix

added missing rotation of normals

Author: Jannik-Hm

pkg/MeshTypes/matrix.go

@@ -43,3 +43,10 @@ func (a Matrix) MulPosition(b Vector) Vector {
 	z := a.X20*b.X + a.X21*b.Y + a.X22*b.Z + a.X23
 	return Vector{x, y, z}
 }
+
+func (a Matrix) MulDirection(b Vector) Vector {
+	x := a.X00*b.X + a.X01*b.Y + a.X02*b.Z
+	y := a.X10*b.X + a.X11*b.Y + a.X12*b.Z
+	z := a.X20*b.X + a.X21*b.Y + a.X22*b.Z
+	return Vector{x, y, z}.Normalize()
+}

pkg/MeshTypes/mesh.go

@@ -31,6 +31,18 @@ func (obj *Mesh) RotateAndTranslate(translationMatrix Matrix) {
 		triangle.V0.Position = translationMatrix.MulPosition(triangle.V0.Position)
 		triangle.V1.Position = translationMatrix.MulPosition(triangle.V1.Position)
 		triangle.V2.Position = translationMatrix.MulPosition(triangle.V2.Position)
+		if triangle.V0.Normal != nil {
+			n0 := translationMatrix.MulDirection(*triangle.V0.Normal)
+			triangle.V0.Normal = &n0
+		}
+		if triangle.V1.Normal != nil {
+			n1 := translationMatrix.MulDirection(*triangle.V1.Normal)
+			triangle.V1.Normal = &n1
+		}
+		if triangle.V2.Normal != nil {
+			n2 := translationMatrix.MulDirection(*triangle.V2.Normal)
+			triangle.V2.Normal = &n2
+		}
 	}
 }
 

tests/MeshTypes/mesh_test.go

@@ -85,6 +85,18 @@ func TestRotateAndTranslate(t *testing.T) {
 		triangle.V0.Position = translationMatrix.MulPosition(triangle.V0.Position) // safe to use as func is tested in another place
 		triangle.V1.Position = translationMatrix.MulPosition(triangle.V1.Position)
 		triangle.V2.Position = translationMatrix.MulPosition(triangle.V2.Position)
+		if triangle.V0.Normal != nil {
+			n0 := translationMatrix.MulDirection(*triangle.V0.Normal)
+			triangle.V0.Normal = &n0
+		}
+		if triangle.V1.Normal != nil {
+			n1 := translationMatrix.MulDirection(*triangle.V1.Normal)
+			triangle.V1.Normal = &n1
+		}
+		if triangle.V2.Normal != nil {
+			n2 := translationMatrix.MulDirection(*triangle.V2.Normal)
+			triangle.V2.Normal = &n2
+		}
 	}
 	if !reflect.DeepEqual(result, want) {
 		t.Errorf("Mesh RotateAndTranslate() Output does not match expected")