Momentum transfer

This image shows different possible paths that result in a collision. Intuitively, we know which way the object should continue along the wall. Determining this mathematically is a bit more challenging.

The object could go in one of two directions. That is, it could follow the wall one way or the other. But why should it prefer one direction over another? We need a generalized rule that applies for every wall and every angle of approach.

The rule is that momentum is transferred along the path of least resistance. Least resistance is the difference between the wall angle and the angle of approach that is less than 90 degrees.

This raises the issue that a line's angle is determined by its direction. This means that the end point we start with determines the angle of the line. See the line below. Is it a 45 degree line, or a 225 degree line? It depends on which point you start from. But, for a generalized rule of momentum transfer, the answer shouldn't matter.

Consider an object moving at 75 degrees and colliding with a 45 degree wall (or a 225 degree wall). | 75 - 45 | = 30. We will transfer momentum into a 45 degree path. If we tried | 75 - 225 | we get 150. Since this is more than 90, we subtract 225 - 180 to determine the correct angle, ie. 45 degrees.

This is how to divert momentum into another path for any angle of approach into a wall, regardless of the angles or directions involved.

Comments

Water Pea Care and Instructions

Please treat your water pea like a real pet fish. Feed daily! Click here to get the Water Pea android app. You will receive a single water pea egg. Drop the egg in the water and your baby pea will hatch. If your water pea is alive after 1 da y, it will produce an egg that you can harvest . Care and Instructions Birth When you place the water pea egg in water, it will take a few seconds for the egg to dissolve. Initially, the newborn water pea will be tiny and hard to see. Take care not to accidentally pick it up and drop it out of the tank. Water peas live for about 3 days if properly fed. Feeding Your water pea must be fed every day, or it will die. To be safe, feed it once in the morning and again at night. Water peas recycle vitamin B by producing caecal pellets . Wait for your water pea to produce the pellet and then collect it so you don't run out of food. This is their only source of nutrition! To collect the pellets, drag them to the top of the ...

Collisions with line intersections

Collisions can be determined by testing for line intersections. Imagine a line representing the ground and an object above, falling down. At time t1 , take the center point p1 of the object. At time t2 , move the object down and take the center point p2 of the object. If the line formed by endpoints (p1, p2) intersect the ground line, a collision has occurred. On a collision, reset the object to its original position before the movement. When a collision occurs, be sure to reset the object by the same point used to determine the line intersection. In this example, I use the center point, so the object should be reset by the center point, not its actual x, y (usually top left) coordinate. It is not always the case that resetting by the x, y coordinate is sufficient. This can be seen in the following picture. It can be seen that even if the object isn't moving, but its size changes, a line intersection can occur, and resetting the object to its x, y position will...

Mean Peas

I did something silly. I'm finishing up some behavioral changes for an aquatic creature that I'm about to release, called a water pea. For fun, I've been playing with different ideas to show the player interesting behaviors. One of those was teaching water peas to be territorial. The way to teach a program to "learn" to do anything is called training. It simply means having the program recognize incorrect (undesired) behaviors, and reinforcing positive behaviors. Over time, the program starts combining a multitude of desired behaviors to produce results that were never explicitly programmed in. These results can be...surprising. I eventually had peas that would fight to protect "their" area of the water tank. But water peas also form friendships, and they won't fight their friends. At least, that was the plan. Most territorial peas simply stayed in their area, along with their friends, and any poor pea that happened to wander by would be killed....

Jelly Shack

Search This Blog