Drawing multiple 2D textures in XNA fast

Question

I am having a performance problem when trying to draw two kinds of 2D textures together in XNA (see code below).

Drawing just the captured frame from a webcam with a mask overlain, I get solid 30 FPS.

Drawing just the Gaussian dots (even if it's a high number of dots), I get solid high FPS, too.

But drawing captured, frame, mask and Gaussian dots together, FPS drop to 15. I however need higher FPS for my application

My question is, how can I achieve higher frame rates (like stable 30 FPS) in this case. What would I have to change?

I am puzzled by a thing: I thought performance would go down with increasing number of Textures2d drawn. However, even if I just draw the frame, mask and add a single Gaussian dot, it goes straight down to 15 FPS - uncreasing the number of Gaussian dot 2d Textures (i.e. the total number of textures drawn) doesn't seem to make a difference any more. So the problem must lie in combining these two different things together.

Can anyone help!

Thanks a lot!

// if residual is enabled, blend the video with the mask
if (configPanel.GetResidualEnabled())
{
    // Turn alpha blending on
    GraphicsDevice.BlendState = BlendState.Additive;

    Texture2D frame = configPanel.GetFrame();

    // Set the channels to write to the R, G, B channels 
    // and draw the first texture using a sprite batch
    spriteBatch.Draw(frame, new Rectangle(
                           0, 0, graphics.PreferredBackBufferWidth, 
                           graphics.PreferredBackBufferHeight),
                           new Rectangle(0, 0, frame.Width, frame.Height), 
                           Color.White, 0.0f, 
                           new Vector2(0, 0), myEffect, 0.0f);

    // Set channels to alpha only, and draw the alpha mask
    spriteBatch.Draw(configPanel.GetMask(), new Vector2(0, 0), Color.White);



    GraphicsDevice.BlendState = BlendState.Opaque;
}
// render the gaussian dots
if (configPanel.GetgaussianDotsEnabled())
{
    Texture2D gaussianDotTexture = configPanel.GetgaussianDot();

    foreach (GaussianDot gaussianDot in configPanel.GetGaussianDotList())
    {
        // Draw the gaussianDot with the correct amount of transparency 
        // and shift them by 1/2 of gaussianDot's size
        if (!configPanel.GetHorizontalFlip())
            spriteBatch.Draw(gaussianDotTexture, 
                        new Vector2(gaussianDot.centreX - 
                        gaussianDotTexture.Width / 2, 
                        gaussianDot.centreY - 
                        gaussianDotTexture.Height / 2), 
                        Color.White * gaussianDot.alpha);
        // if the box is checked, flip the horizontal by shifting the centres
        else
            spriteBatch.Draw(configPanel.GetgaussianDot(), 
                        new Vector2(graphics.PreferredBackBufferWidth - 
                        (gaussianDot.centreX + gaussianDotTexture.Width / 2), 
                        gaussianDot.centreY - gaussianDotTexture.Height / 2), 
                        Color.White * gaussianDot.alpha);
    }
}

Answer 1

Can't really tell what's the cause in your code. You should profile your application using the Analyze menu in Visual Studio, leave it running for a while then stop it and look at the Sample Profiling Report.

Then find which places in your code are marked as hot such as the example below.