Question

I have a problem which I can’t seem to find a different solution for at the moment that is a bit more efficient to my current idea.

I am making a little game with XNA which will have a randomly generated path to move along, but I don’t know how to separate the textures above and below the lines, since the lines are randomly generated. I hope this image can explain the problem:

So the line(s) are randomly added. My own idea was to create a lot of rectangles with different heights and position them next to each other, but I think that is a little bit inefficient and it also forces me the line to be thick enough such that the rectangle can be a bit wider than only 1-2 pixel, otherwise you might see some “emtpy” spots near the line.

If anything is unclear, please feel free to ask and I will add it to the question, but I think my problem should be clear enough.

Answer 1

You could replace pixels you don’t need with transparent pixels:

//extract pixel data from texture
Texture2D topTexture = ...
Color[] topTextureData = new Color[topTexture.Width * topTexture.Height];
topTexture.GetData<Color>(topTextureData);

for(int x = 0; x < topTexture.Width; x++)
{
    //depending on how you represent lines, set transparent all the pixels at and below line
    //basically, for each x dimension, you find where the line is - you have to
    //write the method for getting this y, as I don't know how you represent lines
    int lineY = GetLineYAtThisX(x);

    //all the pixels at (and below) the line are set transparent
    for(int y = lineY; y < topTexture.Height; y++)
    {
        topTextureData[x + y * topTexture.Width] = Color.Transparent;
    }  
}

//save this data into another texture, so you don't ruin the original one.
Texture2D maskedTopTexture = new Texture2D(GraphicsDevice, topTexture.Width, topTexture.Height);
maskedTopTexture.SetData<Color>(topTextureData);

You don’t even have to do this for the bottom one, just draw the top one above it.