Creating a basic glow effect

1

Hi i’m trying to create a basic bloom/glow effect, i found the following https://github.com/Kosmonaut3d/BloomFilter-for-Monogame-and-XNA I’m using the BloomCrossPlatform version.

This works great on white, yellow and somewhat on cyan lines.

But it seems to have no effect on red, green, blue and so on.

What is wrong?

image.png800×480 27.9 KB

Code:

private SpriteBatch spriteBatch;
private BloomFilter bloomFilter;
private RenderTarget2D lineRenderTarget;

private int Width => GraphicsDevice.Viewport.Width;
private int Height => GraphicsDevice.Viewport.Height;

public TitleScreen(Game game)
    : base(game)
{
    game.IsMouseVisible = true;
}

public override void LoadContent()
{
    base.LoadContent();
    spriteBatch = new SpriteBatch(GraphicsDevice);
    lineRenderTarget = new RenderTarget2D(GraphicsDevice, Width, Height, false, SurfaceFormat.Color, DepthFormat.None, 0, RenderTargetUsage.DiscardContents);
    bloomFilter = new BloomFilter();
    bloomFilter.Load(GraphicsDevice, Content, Width, Height);
    bloomFilter.BloomPreset = BloomFilter.BloomPresets.SuperWide;

    bloomFilter.BloomThreshold = 0;
    bloomFilter.BloomStrengthMultiplier = 1;
    //background = Content.Load<Texture2D>("title-screen");
}

public override void UnloadContent()
{
    base.UnloadContent();
    bloomFilter.Dispose();
}
int lineWidth = 2;

public override void Update(GameTime gameTime)
{
    var mouseState = MouseExtended.GetState();
    var keyboardState = KeyboardExtended.GetState();

    if (keyboardState.WasKeyJustDown(Keys.Escape))
        Game.Exit();

    if (keyboardState.WasKeyJustDown(Keys.F1)) bloomFilter.BloomPreset = BloomFilter.BloomPresets.Wide;
    if (keyboardState.WasKeyJustDown(Keys.F2)) bloomFilter.BloomPreset = BloomFilter.BloomPresets.SuperWide;
    if (keyboardState.WasKeyJustDown(Keys.F3)) bloomFilter.BloomPreset = BloomFilter.BloomPresets.Focussed;
    if (keyboardState.WasKeyJustDown(Keys.F4)) bloomFilter.BloomPreset = BloomFilter.BloomPresets.Small;
    if (keyboardState.WasKeyJustDown(Keys.F5)) bloomFilter.BloomPreset = BloomFilter.BloomPresets.Cheap;
    if (keyboardState.WasKeyJustDown(Keys.F9)) bloomFilter.BloomStreakLength = 1;
    if (keyboardState.WasKeyJustDown(Keys.F10)) bloomFilter.BloomStreakLength = 2;
    if (keyboardState.WasKeyJustDown(Keys.D1)) lineWidth = 1;
    if (keyboardState.WasKeyJustDown(Keys.D2)) lineWidth = 2;
    if (keyboardState.WasKeyJustDown(Keys.D3)) lineWidth = 3;
    if (keyboardState.WasKeyJustDown(Keys.D4)) lineWidth = 4;

    if (mouseState.LeftButton == ButtonState.Pressed)
    {
        float x = (float)mouseState.Position.X / Width;
        float y = (float)mouseState.Position.Y / Height;

        bloomFilter.BloomThreshold = x;
        bloomFilter.BloomStrengthMultiplier = y;
    }

    /*if (mouseState.LeftButton == ButtonState.Pressed || keyboardState.WasAnyKeyJustDown())
        ScreenManager.LoadScreen(new PongGameScreen(Game), new FadeTransition(GraphicsDevice, Color.Black, 0.5f));*/
}
public override void Draw(GameTime gameTime)
{
    GraphicsDevice.SetRenderTarget(lineRenderTarget);
    GraphicsDevice.Clear(Color.Black);

    spriteBatch.Begin(samplerState: SamplerState.PointClamp);

    var d = (gameTime.TotalGameTime.TotalSeconds % 10) / 10;

    spriteBatch.DrawLine(new Vector2(Width / 2, Height / 2), 100, (float)(d * Math.PI * 2), Color.White, lineWidth);
    spriteBatch.DrawLine(new Vector2(Width / 2, Height / 2), 100, (float)(d * Math.PI * 2 + Math.PI * 0.25), Color.Red, lineWidth);
    spriteBatch.DrawLine(new Vector2(Width / 2, Height / 2), 100, (float)(d * Math.PI * 2 + Math.PI * 0.5), Color.Green, lineWidth);
    spriteBatch.DrawLine(new Vector2(Width / 2, Height / 2), 100, (float)(d * Math.PI * 2 + Math.PI * 0.75), Color.Blue, lineWidth);
    spriteBatch.DrawLine(new Vector2(Width / 2, Height / 2), 100, (float)(d * Math.PI * 2 + Math.PI * 1), Color.Yellow, lineWidth);
    spriteBatch.DrawLine(new Vector2(Width / 2, Height / 2), 100, (float)(d * Math.PI * 2 + Math.PI * 1.25), Color.Magenta, lineWidth);
    spriteBatch.DrawLine(new Vector2(Width / 2, Height / 2), 100, (float)(d * Math.PI * 2 + Math.PI * 1.5), Color.Cyan, lineWidth);
    spriteBatch.DrawLine(new Vector2(Width / 2, Height / 2), 100, (float)(d * Math.PI * 2 + Math.PI * 1.75), Color.Orange, lineWidth);
    spriteBatch.End();

    Texture2D bloom = bloomFilter.Draw(lineRenderTarget, Width, Height);
    GraphicsDevice.SetRenderTarget(null);
    spriteBatch.Begin(blendState: BlendState.Additive);
    //GraphicsDevice.Clear(Color.Black);
    spriteBatch.Draw(lineRenderTarget, new Rectangle(0, 0, Width, Height), Color.White);
    spriteBatch.Draw(bloom, new Rectangle(0, 0, Width, Height), Color.White);
    spriteBatch.End();
}

Source: https://ufile.io/opag3

2

Red, green and blue are darker than the other colors because they only use a single color channel. The other colors combine multiple primary colors. E.g. yellow is red and green combined. White is the brightest because it combines all three primary colors (red, green and blue).

Can you increase the BloomStrengthMultiplier to above 1 to get a stronger effect?

You could also switch your lineRenderTarget to a floating point render target. That way you can increase the brightness of objects far beyond what you can do with a SurfaceFormat.Color render target. Your shaders may need some changes to support that though, not sure about that.

1 Like
3

In the Sample of the Bloom effect you can click/drag the mouse to see different strengths, you’ll notice reds get affected later since it’s a bit darker.

However, you can check the shader that evaluates the threshold and manipulate it to be more sensitive to red/green