How to create randomly generated, but static background elements within a draw loop

CS Discoveries Unit and Lesson Discussion
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1

I wanted to draw a night scene with several 100 randomly drawn stars (points). I can create the loop that draws the stars, but when I animated a drawing (a car), the process of everything in the draw loop repeating itself constantly redraws the randomly located stars when I want them to stay in the same place. If I draw them outside the draw loop, the background hides them when it runs inside the draw loop.

Any ideas on how to overcome this?

Mike

2

Mike, can you post your code so I can help debug the problem?

3

Here’s a link to my project …

I have created a partial work around by drawing a blue rectangle where my car passes on the screen, but that still doesn’t work well and I know it’s not the right solution. The only real solution I can think of is somehow creating a .jpg or .png with the stars already on it, but that’s not the solution I want either.

thanks for looking at it.

Mike

4

@mwood
Very creative project.
I made a small change to your code. Take a look. Draw the background inside the draw loop with the stars.

background("darkblue");

Link: https://studio.code.org/projects/gamelab/P3P-wtms3O0j-UV4GD14g4OoQ-INCJgB0M6RJHRfc7g

5

Thanks for looking at it … I had hoped to draw the stars once and then leave them in their originally drawn position … that’s where the problem is because when it draws the background again, I have to draw the stars again and it draws them in a different random position so it looks more like a snowstorm … maybe I need an array that stores the original position of the stars, but I haven’t learned how to do that yet in GameLab if it’s possible. I’ll keep working on it. :slight_smile:

6

@mwood an array would be one solution, but the other would be to use sprites.

Array example https://studio.code.org/projects/gamelab/tjfDaHK0vOH6UWnCBMqWCA/view
Sprites example https://studio.code.org/projects/gamelab/NOccI7-JQdvJcTdMA3Yilg/view

I left the random stroke width in the draw loop for the array example to give the stars a twinkle, but you could place those values in an array as well.

7

Thanks Josh. I like the twinkling affect and I appreciate you showing me two ways to accomplish this. I knew it could be done.

Mike