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Creating a Basic Effect

Demonstrates how to create and initialize an instance of the BasicEffect class and use it to draw simple geometry.
Bb203926.note(en-us,XNAGameStudio.41).gifNote
The steps described here apply to effects created with the BasicEffect class. Use the Effect class to write a custom effect. The example draws aliased geometry. To see an example that draws smoother edges because it also applies antialiasing, see Enabling Antialiasing (Multisampling).

Bb203926.graphics_use_basic_effect(en-us,XNAGameStudio.41).jpg

The Complete Sample

You can download a complete code sample for this topic, including full source code and any additional supporting files required by the sample.

Using BasicEffect

To use BasicEffect

Using the basic effect class requires a set of world, view, and projection matrices, a vertex buffer, a vertex declaration, and an instance of the BasicEffect class.

  1. Declare these objects at the beginning of the game.

    Matrix worldMatrix;
    Matrix viewMatrix;
    Matrix projectionMatrix;
    VertexPositionNormalTexture[] cubeVertices;
    VertexDeclaration vertexDeclaration;
    VertexBuffer vertexBuffer;
    BasicEffect basicEffect;
    
  2. Initialize the world, view, and projection matrices.

    In this example, you create a world matrix that rotates the geometry 22.5 degrees along the x and y axes. The view matrix is a look-at matrix with a camera position at (0, 0, 5), pointing at the origin. The projection matrix is a perspective projection matrix based on a a 45-degree field of view, an aspect ratio equal to the client window, and a set of near and far planes.

    float tilt = MathHelper.ToRadians(0);  // 0 degree angle
    // Use the world matrix to tilt the cube along x and y axes.
    worldMatrix = Matrix.CreateRotationX(tilt) * Matrix.CreateRotationY(tilt);
    viewMatrix = Matrix.CreateLookAt(new Vector3(5, 5, 5), Vector3.Zero, Vector3.Up);
    
    projectionMatrix = Matrix.CreatePerspectiveFieldOfView(
        MathHelper.ToRadians(45),  // 45 degree angle
        (float)GraphicsDevice.Viewport.Width /
        (float)GraphicsDevice.Viewport.Height,
        1.0f, 100.0f);
    
  3. Initialize BasicEffect with transformation and light values.

    basicEffect = new BasicEffect(graphics.GraphicsDevice);
    
    basicEffect.World = worldMatrix;
    basicEffect.View = viewMatrix;
    basicEffect.Projection = projectionMatrix;
    
    // primitive color
    basicEffect.AmbientLightColor = new Vector3(0.1f, 0.1f, 0.1f);
    basicEffect.DiffuseColor = new Vector3(1.0f, 1.0f, 1.0f);
    basicEffect.SpecularColor = new Vector3(0.25f, 0.25f, 0.25f);
    basicEffect.SpecularPower = 5.0f;
    basicEffect.Alpha = 1.0f;
    
    basicEffect.LightingEnabled = true;
    if (basicEffect.LightingEnabled)
    {
        basicEffect.DirectionalLight0.Enabled = true; // enable each light individually
        if (basicEffect.DirectionalLight0.Enabled)
        {
            // x direction
            basicEffect.DirectionalLight0.DiffuseColor = new Vector3(1, 0, 0); // range is 0 to 1
            basicEffect.DirectionalLight0.Direction = Vector3.Normalize(new Vector3(-1, 0, 0));
            // points from the light to the origin of the scene
            basicEffect.DirectionalLight0.SpecularColor = Vector3.One;
        }
    
        basicEffect.DirectionalLight1.Enabled = true;
        if (basicEffect.DirectionalLight1.Enabled)
        {
            // y direction
            basicEffect.DirectionalLight1.DiffuseColor = new Vector3(0, 0.75f, 0);
            basicEffect.DirectionalLight1.Direction = Vector3.Normalize(new Vector3(0, -1, 0));
            basicEffect.DirectionalLight1.SpecularColor = Vector3.One;
        }
    
        basicEffect.DirectionalLight2.Enabled = true;
        if (basicEffect.DirectionalLight2.Enabled)
        {
            // z direction
            basicEffect.DirectionalLight2.DiffuseColor = new Vector3(0, 0, 0.5f);
            basicEffect.DirectionalLight2.Direction = Vector3.Normalize(new Vector3(0, 0, -1));
            basicEffect.DirectionalLight2.SpecularColor = Vector3.One;
        }
    }
    
  4. Create a vertex declaration for the type VertexPositionNormalTexture.

    • If lighting is enabled, the vertex must have a normal type.

    • If vertex colors are enabled, the vertex must have colors.

    • If texturing is enabled, the vertex must have a texture coordinate.

    vertexDeclaration = new VertexDeclaration(new VertexElement[]
        {
            new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0),
            new VertexElement(12, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0),
            new VertexElement(24, VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 0)
        }
    );
    
  5. Create the per vertex data. This example shows the data for one face of the cube.

    Vector3 topLeftFront = new Vector3(-1.0f, 1.0f, 1.0f);
    Vector3 bottomLeftFront = new Vector3(-1.0f, -1.0f, 1.0f);
    Vector3 topRightFront = new Vector3(1.0f, 1.0f, 1.0f);
    Vector3 bottomRightFront = new Vector3(1.0f, -1.0f, 1.0f);
    Vector3 topLeftBack = new Vector3(-1.0f, 1.0f, -1.0f);
    Vector3 topRightBack = new Vector3(1.0f, 1.0f, -1.0f);
    Vector3 bottomLeftBack = new Vector3(-1.0f, -1.0f, -1.0f);
    Vector3 bottomRightBack = new Vector3(1.0f, -1.0f, -1.0f);
    
    Vector2 textureTopLeft = new Vector2(0.0f, 0.0f);
    Vector2 textureTopRight = new Vector2(1.0f, 0.0f);
    Vector2 textureBottomLeft = new Vector2(0.0f, 1.0f);
    Vector2 textureBottomRight = new Vector2(1.0f, 1.0f);
    
    Vector3 frontNormal = new Vector3(0.0f, 0.0f, 1.0f);
    Vector3 backNormal = new Vector3(0.0f, 0.0f, -1.0f);
    Vector3 topNormal = new Vector3(0.0f, 1.0f, 0.0f);
    Vector3 bottomNormal = new Vector3(0.0f, -1.0f, 0.0f);
    Vector3 leftNormal = new Vector3(-1.0f, 0.0f, 0.0f);
    Vector3 rightNormal = new Vector3(1.0f, 0.0f, 0.0f);
    
    // Front face.
    cubeVertices[0] =
        new VertexPositionNormalTexture(
        topLeftFront, frontNormal, textureTopLeft);
    cubeVertices[1] =
        new VertexPositionNormalTexture(
        bottomLeftFront, frontNormal, textureBottomLeft);
    cubeVertices[2] =
        new VertexPositionNormalTexture(
        topRightFront, frontNormal, textureTopRight);
    cubeVertices[3] =
        new VertexPositionNormalTexture(
        bottomLeftFront, frontNormal, textureBottomLeft);
    cubeVertices[4] =
        new VertexPositionNormalTexture(
        bottomRightFront, frontNormal, textureBottomRight);
    cubeVertices[5] =
        new VertexPositionNormalTexture(
        topRightFront, frontNormal, textureTopRight);
    
  6. Call GraphicsDevice.Clear to clear the render target.

  7. Set the rasterizer state to turn off culling using the RasterizerState property.

  8. Call EffectPass.Apply to set the effect state in preparation for rendering.

  9. Draw the geometry by calling GraphicsDevice.DrawPrimitives.

    graphics.GraphicsDevice.Clear(Color.SteelBlue);
    
    RasterizerState rasterizerState1 = new RasterizerState();
    rasterizerState1.CullMode = CullMode.None;
    graphics.GraphicsDevice.RasterizerState = rasterizerState1;
    foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes)
    {
        pass.Apply();
    
        graphics.GraphicsDevice.DrawPrimitives(
            PrimitiveType.TriangleList,
            0,
            12
        );
    }
    
    
    base.Draw(gameTime);
    

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