# Creating an invisible circle for collision

This topic is 2170 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

As my first project I'm working on a tower defence game. The project is somewhere near 60% finished, including particles and all.
But I got stuck at coding the enemies and towers. I need an invisible circle that can be used to detect collision. If the enemy is in this circle (the circle is the range of the tower), the tower should start shooting. I also should be able to adjust the circle to the range of every tower, which can be upgraded. I already searched on some sites but I can't find a way to do this.
Can someone give me an example on how to do this?

##### Share on other sites
Then just take the distance, or square distance, between enemy and tower to determine if it is inside the effect radius:
 for each enemy do delta.x = enemy.x - tower.x delta.y = enemy.y - tower.y // square distance = dotProduct(delta,delta) square_distance = delta.x*delta.x+delta.y*delta.y // check if inside radius if( square_distance <= (radius*radius) then .. shoot at enemy end end  Edited by Ashaman73

##### Share on other sites
Yes that should work. But in C++ the script would be even easier I think, I'll figure something out. Thanks!

• 16
• 9
• 13
• 41
• 15