我无法让我的投影矩阵为旋转动画提供正确的视角

Question

我m trying to replicate a plane projection rotation in UWP using the composition api. But I'm having trouble with a projection matrix in my composition code. Here我有：

private void Perspective(FrameworkElement element, double duration, float rotationDepth = 750f)
{
    var parent = ElementCompositionPreview.GetElementVisual(element.Parent as FrameworkElement);

    var width = (float)element.ActualWidth;
    var height = (float)element.ActualHeight;
    var halfWidth = (float)(width / 2.0);
    var halfHeight = (float)(height / 2.0);

    // Initialize the Compositor
    var visual = ElementCompositionPreview.GetElementVisual(element);

    // Create Scoped batch for animations
    var batch = visual.Compositor.CreateScopedBatch(CompositionBatchTypes.Animation);

    // Rotation animation
    var projectionMatrix = new Matrix4x4(1, 0, 0, 0,
                                            0, 1, 0, 0,
                                            0, 0, 1, 1 / rotationDepth,
                                            0, 0, 0, 1);

    // To ensure that the rotation occurs through the center of the visual rather than the
    // left edge, pre-multiply the rotation matrix with a translation that logically shifts
    // the axis to the point of rotation, then restore the original location
    parent.TransformMatrix = Matrix4x4.CreateTranslation(-halfWidth, -halfHeight, 0) *
                            projectionMatrix *
                            Matrix4x4.CreateTranslation(halfWidth, halfHeight, 0);

    // Rotate along the Y-axis
    visual.RotationAxis = new Vector3(0, 1, 0);
    visual.CenterPoint = new Vector3(halfWidth, halfHeight, 0f);
    visual.RotationAngleInDegrees = 0.0f;

    var rotateAnimation = visual.Compositor.CreateScalarKeyFrameAnimation();

    rotateAnimation.InsertKeyFrame(0.0f, 90);
    rotateAnimation.InsertKeyFrame(1f, 0);
    rotateAnimation.Duration = TimeSpan.FromMilliseconds(duration);

    visual.StartAnimation("RotationAngleInDegrees", rotateAnimation);

    // Batch is ended an no objects can be added
    batch.End();
}

所以上面这段代码会沿Y轴旋转。在下面的 gif 中，您会看到我在另一个由 PlaneProjection 驱动的动画之上制作动画以进行比较：

两者的"perspective"都很好，都在中间。现在让我们更改这行代码以将其切换为在 X 轴上旋转：

// Rotate along the Y-axis
visual.RotationAxis = new Vector3(0, 1, 0);

现在请注意下面的 gif：

合成动画似乎在旋转，视角更偏右，而不是完全居中。我的投影矩阵需要改变吗？

Answer 1

快速回答。

yourVisual.Offset = new Vector3((float)Window.Current.Bounds.Width / 2, (float)Window.Current.Bounds.Height / 2, 0);

这样就可以了。应用了变换矩阵的移位视觉对象。没有它，你的视角中心是左上角。

Answer 2

终于得到修复，如前所述 here，只需用容器包装受影响的控件即可解决问题：

所以在我的 Xaml 我有：

<Border Width="300"
        Height="250"
        Background="LightSeaGreen"
        x:Name="Persp"
        Margin="0,0,0,40">
    <TextBlock Text="Composition"
                FontSize="28"
                HorizontalAlignment="Center"
                VerticalAlignment="Center"
                FontWeight="Bold"
                Foreground="White" />
</Border>

我改成了：

<Border Width="300"
        Height="250">
    <Border Background="LightSeaGreen"
            x:Name="Persp"
            Margin="0,0,0,40">
        <TextBlock Text="Composition"
                    FontSize="28"
                    HorizontalAlignment="Center"
                    VerticalAlignment="Center"
                    FontWeight="Bold"
                    Foreground="White" />
    </Border>
</Border>

我无法让我的投影矩阵为旋转动画提供正确的视角

I can't get my Projection Matrix to have a proper perspective for a Rotation animation

uwp

xaml-composition

windows-composition-api