问题描述
我在 Monogame/XNA 中遇到了问题,我将位置/旋转/比例存储在矩阵中,以便更轻松地通过育儿操作这些值。一切似乎都很顺利,除了当我旋转矩阵时,对象似乎在四处抖动和摇晃。相关代码如下:
// Executes every frame
internal void Draw()
{
float RadRot = MathHelper.Toradians(Rotation);
// Sets world matrix for things that draw
if (Parent != null) {
WorldMatrix = Matrix.CreateScale(Size.X,Size.Y,1) * -Matrix.CreateTranslation(Pivot.X,Pivot.Y,0) * Matrix.CreateRotationZ(RadRot);
WorldMatrix.Translation = Vector3.Zero; // Rotating seems to create a strange positioning issue,this fixes it
WorldMatrix *= Matrix.CreateTranslation(RelativePosition.X,RelativePosition.Y,0) * Matrix.CreateRotationZ(MathHelper.Toradians(Parent.Rotation)) * <FIX JITTER> * Matrix.CreateTranslation(Parent.DecomposedPosition.X,Parent.DecomposedPosition.Y,0);
} else
{
// For objects without parents
WorldMatrix = Matrix.CreateScale(RelativeSize.X,RelativeSize.Y,0) * Matrix.CreateRotationZ(RadRot);
WorldMatrix.Translation = Vector3.Zero; // This fixes the jitter issue,but in the code above (in the if statement),I can't do this when translating the child around the parent
WorldMatrix *= Matrix.CreateTranslation(RelativePosition.X,0);
}
Vector3 TempPos = Vector3.Zero;
Quaternion TempRot = Quaternion.Identity;
Vector3 TempSize = Vector3.Zero;
WorldMatrix.Decompose(out TempSize,out TempRot,out TempPos);
DecomposedPosition = new Vector2(-TempPos.X,-TempPos.Y);
DecomposedRotation = MathHelper.Toradians(Rotation); // Can't convert quaternions,but this works
DecomposedSize = new Vector2(MathF.Round(TempSize.X),MathF.Round(TempSize.Y));
foreach (Component2D comp in Components)
{
comp.Draw();
}
}
这是 comp.Draw 调用的:
MyGame.SpriteDrawing.Draw(Image,new Rectangle(Linkedobject.DecomposedPosition.ToPoint(),Linkedobject.DecomposedSize.ToPoint()),RenderRegion,Color,Linkedobject.DecomposedRotation,Linkedobject.Pivot,SpriteEffects.None,Linkedobject.Layer + (SubLayer / 10000));
这是它的实际效果:
额外注意:无论对象的大小如何,都会发生这种抖动
解决方法
尝试以不同的方式组织场景:
- 每个对象都可以存储它的比例 (Vector3)、旋转 (Quaternion) 和位置 (Vector3)
- 每个对象都应该有一个结果矩阵的属性(在局部空间中),这将是这样的乘法,按以下顺序:Matrix.CreateScale(scale) * Matrix.CreateRotationQuaterion(rotation) * Matrix.CreateTranslation(position) )
- 现在,当你有了上面的局部空间矩阵时,用它来创建 WorldMatrix,它是父世界矩阵和这个对象局部空间矩阵的乘法,或者只有局部空间矩阵 - 当没有父存在时。
- 尽量只将每个元素的世界矩阵传递给你的绘图代码,避免分解
- 如果你有一个很大的层次结构,你可以在不改变的情况下缓存本地矩阵结果
看来我只是使用了错误的 SpriteBatch.Draw()
。我使用的是 Rectangle 版本,而我所需要的只是使用 Vector2 版本来防止舍入错误。
MyGame.SpriteDrawing.Draw(Image,LinkedObject.DecomposedPosition,RenderRegion,Color,LinkedObject.DecomposedRotation,LinkedObject.Pivot * RenderRegion.Size.ToVector2(),LinkedObject.DecomposedSize / RenderRegion.Size.ToVector2(),SpriteEffects.None,LinkedObject.Layer + (SubLayer / 10000));