Preface

Blogger Homepage ： A Feng's homepage _CSDN

scratch It is a programming tool mainly for children , There are also many big friends like it , Because it does Simple and interesting , By building blocks , You can build some interesting programs .
We've played 4399 Is the tank turbulent ？ Have you tried to realize it by yourself ？ This article records my use of scratch Try to realize the process of tank turbulence Games , Some of the problems we encountered .

In the process of making the program , I referred to b Video of the station , A video link is attached below .
Programming tools ：scratch Web version
Reference material ：scratch Tanks war -b standing
Get full code ：.sb3 Complete source code

1. Program demonstration

2. Through wall control

The solution of through wall control comes from the beginning of the article b standing up Lord
In the process of realizing the through wall control of character movement , I am used to using such logic ：

1） Move in the specified direction
2） Check whether it touches the wall
3） If you come across , Then return to the original position

in other words , I put every time motion and Wall impact detection Bound together , But then I found one problem ：

In order to make the tank move more smoothly , Every movement Stride They are all designed to be small . So if a part of the tank is already on the wall , At this point we No matter which direction you move , Will detect touching the wall , Then return to the original position .
in other words , The tank will get stuck on the wall .
But the rotation of the tank model , It often leads to the situation of some walls , Hard to avoid .

Solution ：

Give the tank The front and back parts are painted with frames of different colors .
effect ： When the front of the tank is on the wall , The tank can move backwards , Get rid of the wall .（ The situation is similar when the rear of the tank is on the wall ）

3. The bullet bounced

3. 1. explain

Be careful ： Here we only realize the situation that the wall is horizontal or vertical
When considering the rebound of bullets , We should be aware of the following problems ：

1） Usually , We need to know about bullets Own direction 、 The direction of the bullet Angle with the wall , We can get the direction after the bullet bounces .
2） Even if only horizontal and vertical walls are considered , There are also two situations . How do we judge the impact Is the wall horizontal or vertical ？

stay scratch Next , Judge the direction of the wall at the time of collision , I'm really a little confused .
But I have an idea behind me ： Use intermediate results .

First assume that only one wall side needs to be considered , Here we consider the horizontal wall , Then the inclination of the wall is fixed , We Just know the direction of the bullet itself You can calculate the direction of the bullet after it bounces , Such as The figure below ：

It's simple to consider only horizontal walls , What should we do with our vertical walls ？ We consider such a factor ： The wall is thick .
Considering all horizontal walls , What happens when a bullet collides with a vertical wall ？ The bullet Still like hitting a horizontal wall Same rebound , Then it must Through the wall , So we can use this feature to judge whether the bullet hit the wall horizontally or vertically ：
1） When the bullet hits the wall , First, press the bullet to hit the horizontal wall Change direction
2） The bullet continued to move a small step in a new direction
3） Check the collision between the bullet and the wall again ：

• If the bullet is now No collision The wall , The bullet has separated from the wall , Explain that the wall is The transverse Of
• otherwise , It means that the bullet is trying to pass through the wall , Then the wall is vertical Of

4） If the wall is vertical , At this point, we will determine the direction of the bullet reverse That is, you can get the correct rebound direction

3. 2. Demonstration of rebound decomposition action

Above is 0, Directly below is 180（-180）, On the right is 90, Positive left is -90

Conclusion

🧭 In the article start , There is complete program source code in csdn Of Download address , Friends in need can download by themselves .
🧭 The main content of this article has ended here ！
🧭 This time, with my own try , Solved a small problem encountered , I still have a sense of achievement .
🧭 If this content sharing helps you , Just support bloggers ！