DrawUserPrimitives无效的操作exception

我正在尝试使用XNA中的此代码绘制三角形：

VertexPositionColor[] vertices = new VertexPositionColor[3]; vertices[0].Position = new Vector3(-0.5f, -0.5f, 0f); vertices[0].Color = Color.Red; vertices[1].Position = new Vector3(0, 0.5f, 0f); vertices[1].Color = Color.Green; vertices[2].Position = new Vector3(0.5f, -0.5f, 0f); vertices[2].Color = Color.Yellow; GraphicsDevice.DrawUserPrimitives(PrimitiveType.TriangleList, vertices, 0, 1); 

但是，只要我运行它，应用程序就会关闭，并抛出InvalidOperationException。 这是WP7应用程序。 我错过了什么吗？ 感谢您的帮助。

Answer 1

文档说DrawUserPrimitives抛出InvalidOperationException ：

在调用DrawUserPrimitives之前未设置有效的顶点着色器和像素着色器。 在执行任何绘制操作之前，必须在设备上设置有效的顶点着色器和像素着色器（或有效效果）。

（它还表示，如果你的顶点无效，它会抛出 – 但它们看起来还不错。）

您需要在图形设备上设置Effect 。 具体来说，您需要在调用DrawUserPrimitives之前调用EffectPass.Apply 。 一个简单的方法是使用BasicEffect 。 这里有一些代码，适合放入Draw方法，以说明这一点：

 // These three lines are required if you use SpriteBatch, to reset the states that it sets GraphicsDevice.BlendState = BlendState.Opaque; GraphicsDevice.DepthStencilState = DepthStencilState.Default; GraphicsDevice.SamplerStates[0] = SamplerState.LinearWrap; // Transform your model to place it somewhere in the world basicEffect.World = Matrix.CreateRotationZ(MathHelper.PiOver4) * Matrix.CreateTranslation(0.5f, 0, 0); // for sake of example //basicEffect.World = Matrix.Identity; // Use this to leave your model at the origin // Transform the entire world around (effectively: place the camera) basicEffect.View = Matrix.CreateLookAt(new Vector3(0, 0, -3), Vector3.Zero, Vector3.Up); // Specify how 3D points are projected/transformed onto the 2D screen basicEffect.Projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45), (float)GraphicsDevice.Viewport.Width / (float)GraphicsDevice.Viewport.Height, 1.0f, 100.0f); // Tell BasicEffect to make use of your vertex colors basicEffect.VertexColorEnabled = true; // I'm setting this so that *both* sides of your triangle are drawn // (so it won't be back-face culled if you move it, or the camera around behind it) GraphicsDevice.RasterizerState = RasterizerState.CullNone; // Render with a BasicEffect that was created in LoadContent // (BasicEffect only has one pass - but effects in general can have many rendering passes) foreach(EffectPass pass in basicEffect.CurrentTechnique.Passes) { // This is the all-important line that sets the effect, and all of its settings, on the graphics device pass.Apply(); // Here's your code: VertexPositionColor[] vertices = new VertexPositionColor[3]; vertices[0].Position = new Vector3(-0.5f, -0.5f, 0f); vertices[0].Color = Color.Red; vertices[1].Position = new Vector3(0, 0.5f, 0f); vertices[1].Color = Color.Green; vertices[2].Position = new Vector3(0.5f, -0.5f, 0f); vertices[2].Color = Color.Yellow; GraphicsDevice.DrawUserPrimitives(PrimitiveType.TriangleList, vertices, 0, 1); } 

Answer 2

当组件发现它处于意外状态时，通常会抛出该exception（InvalidOperationException）。 因此，在您的情况下，请确保在调用DrawUserPrimitives之前，GraphicsDevice不需要设置其他一些属性。