ReadBackbufferTest

ReadBackbufferTest.cs

/* SpriteBatch Stress Test
 * Written by Ethan "flibitijibibo" Lee
 * http://www.flibitijibibo.com/
 *
 * Released under public domain.
 * No warranty implied; use at your own risk.
 */

using System.IO;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

namespace MSAATest
{
    class MSAATest : Game
    {
        GraphicsDeviceManager gdm;
        RenderTarget2D rt;
        SpriteBatch batch;

        VertexBuffer vertexBuffer;
        BasicEffect basicEffect;
        Matrix world = Matrix.CreateTranslation(0, 0, 0);
        Matrix view = Matrix.CreateLookAt(new Vector3(0, 0, 3), new Vector3(0, 0, 0), new Vector3(0, 1, 0));
        Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45), 800f / 480f, 0.01f, 100f);

        // Test different combinations!
        private const bool TEST_MSAA_BACKBUFFER = true;
        private const bool TEST_MSAA_RENDER_TARGETS = true;
        private const int SAMPLE_COUNT = 8;
        
        public bool CanSaveThisFrame { get; private set; } = true;
        public bool SaveThisFrame { get; private set; } = false;

        public MSAATest() : base()
        {
            gdm = new GraphicsDeviceManager(this);

            if (TEST_MSAA_BACKBUFFER)
            {
                gdm.PreferMultiSampling = true;
            }
        }

        protected override void Initialize()
        {
            if (TEST_MSAA_BACKBUFFER)
            {
                GraphicsDevice.PresentationParameters.MultiSampleCount = SAMPLE_COUNT;
                gdm.ApplyChanges();
            }

            basicEffect = new BasicEffect(GraphicsDevice);

            VertexPositionColor[] vertices = new VertexPositionColor[3];
            vertices[0] = new VertexPositionColor(new Vector3(0, 1, 0), Color.Red);
            vertices[1] = new VertexPositionColor(new Vector3(+0.5f, 0, 0), Color.Green);
            vertices[2] = new VertexPositionColor(new Vector3(-0.5f, 0, 0), Color.Blue);

            vertexBuffer = new VertexBuffer(GraphicsDevice, typeof(VertexPositionColor), 3, BufferUsage.WriteOnly);
            vertexBuffer.SetData<VertexPositionColor>(vertices);

            rt = new RenderTarget2D(GraphicsDevice, 800, 480, false, SurfaceFormat.Color, DepthFormat.None, SAMPLE_COUNT, RenderTargetUsage.DiscardContents);
            batch = new SpriteBatch(GraphicsDevice);

            base.Initialize();
        }

        protected override void Update(GameTime gameTime)
        {
            if (Keyboard.GetState().IsKeyUp(Keys.S))
            {
                CanSaveThisFrame = true;
            }
            
            if (CanSaveThisFrame && Keyboard.GetState().IsKeyDown(Keys.S))
            {
                SaveThisFrame = true;
                CanSaveThisFrame = false;
            }
        }

        protected override void Draw(GameTime gameTime)
        {
            if (TEST_MSAA_RENDER_TARGETS)
            {
                GraphicsDevice.SetRenderTarget(rt);
                GraphicsDevice.Clear(Color.Transparent);
            }
            else if (TEST_MSAA_BACKBUFFER)
            {
                GraphicsDevice.SetRenderTarget(null);
                GraphicsDevice.Clear(Color.Black);
            }

            basicEffect.World = world;
            basicEffect.View = view;
            basicEffect.Projection = projection;
            basicEffect.VertexColorEnabled = true;

            GraphicsDevice.SetVertexBuffer(vertexBuffer);

            RasterizerState rasterizerState = new RasterizerState();
            rasterizerState.CullMode = CullMode.None;
            GraphicsDevice.RasterizerState = rasterizerState;

            foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes)
            {
                pass.Apply();
                GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleList, 0, 1);
            }

            if (TEST_MSAA_RENDER_TARGETS)
            {
                // Draw the render target
                GraphicsDevice.SetRenderTarget(null);
                GraphicsDevice.Clear(Color.Black);

                batch.Begin();
                batch.Draw(rt, Vector2.Zero, Color.White);
                batch.End();
            }

            if (SaveThisFrame)
            {
                int[] backBufferData = new int[GraphicsDevice.PresentationParameters.BackBufferWidth * GraphicsDevice.PresentationParameters.BackBufferHeight];
                GraphicsDevice.GetBackBufferData(backBufferData);
                Texture2D texture = new Texture2D(GraphicsDevice, GraphicsDevice.PresentationParameters.BackBufferWidth, GraphicsDevice.PresentationParameters.BackBufferHeight);
                texture.SetData(backBufferData);
                Stream stream = File.OpenWrite("readBackBuffer.png");
                texture.SaveAsPng(stream, GraphicsDevice.PresentationParameters.BackBufferWidth, GraphicsDevice.PresentationParameters.BackBufferHeight);
                stream.Dispose();
                texture.Dispose();

                SaveThisFrame = false;
            }
        }

        public static void Main(string[] args)
        {
            using (MSAATest game = new MSAATest())
            {
                game.Run();
            }
        }
    }
}