If an SKSpriteNode runs an SKAction telling it to move by a certain vector for a duration, will the SKSpriteNode still have momentum and keep moving once the action is complete? Also, if another action is called telling the node to move along a different vector while it is still moving by the first vector, will the node listen to only the second vector, only the first, or both? Thanks in advance!
SKActions and the physics are separate. The action will run and ignore all of the physics, and the previous vector. You should use applyForce if you want it to move by a certain amount.
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I'm attempting to write a bouncing ball game using flame in flutter. To detect collisions the onCollision and onCollisionStart methods are provided. What I had hoped is that onCollisionStart would give a precise location when two objects first hit each other. However, instead it gives a list of positions indicating where the two objects overlap after the first game-tick when this happens (i.e. onCollisionStart is called at the same time as onCollision, but is not called a second time if the same two objects are still colliding on the next tick).
This is illustrated in the attached picture. The collision points are marked with red dots. If the ball were moving downwards, then the ball would have hit the top of the rectangle and so should bounce upwards. However, if the ball were moving horizontally, then its first point of contact would have been the top left corner of the box, and the ball would bounce upwards and to the left.
If I want to work out correct angle that the ball should fly off, then I would need to do some clever calculations to work out the point that the ball first started hitting the other object (those calculations would depend on the precise shape of the other object). Is there some way to work out the point at which the two objects first started colliding? Thanks
What you usually need for this is the normal of the collision, but unfortunately we don't have that for the collision detection system yet.
We do have it in the raytracing system though, so what you could do is send out a ray and see how it will bounce and then just bounce the ball in the same way.
If you don't want to use raytracing I suggest that you calculate the direction of the ball, which you might already have, but if you don't you can just store the last position and subtract it from the current position.
After that you need to find the normals of the edges where the intersection points are.
Let's say the ball direction vector is v, and the two normal vectors are n1 and n2.
Calculate the dot product (this is build in to the vector_math library) of the ball direction vector and each of the normal vectors:
dot1 = v.dot(n1)
dot2 = v.dot(n2)
Compare the results of the dot products:
If dot1 > 0, n1 is facing the ball.
If dot2 > 0, n2 is facing the ball.
After that you can use v.reflect(nx) to get the direction where your ball should be going (where nx is the normal facing the ball).
Hopefully we'll have this built-in to Flame soon!
I need to create 2 animations,
one is of an object going from point A to point B at a constant velocity.
the other is of an object starting from point A but with a gradually decreasing velocity as it reaches point B until it comes to a stop.
I tried decreasing the animation speed every second to achieve this result with no luck.
Any ideas?
As you may have noticed when you work with animation in Unity there is no such thing as changing the velocity of an object. What you need to do is give your object an Animator and create a new Animation.
Then on the animation timeline press the red dot (record button) and then place your object on point A.
Next, on the time line you want to select the exact second that you want your object to come to a stop and after that move the object on point B.
Now, the more seconds there are in between the 2 keys, the more time it's going to take for the object to travel.
To make it gradually slower instead of it just travelling slowly:
On the animation panel you will see 2 tabs. Dopesheet and Curves. Hit Curves and play around with them till you have a satisfing result.
Documentation on using Curves
I'm making a SpriteKit game where two SpriteNodes are in a maze. That maze is represented as a grid. One sprite (A) travels faster than the other (B). Items randomly pop up, and the sprites have to collect them.
Pathfinding is easy (GKGridGraph is simple to use).
Here's the problem: At any given time, A and B could be on the same stretch of the maze. If A is behind B, I want A to be forced to go the same speed as B (cannot pass through or around). How can I accomplish this?
Thank you for your time!
I am creating a 2D autoscroller and when my player (with a circle physicsBody) collides with an SKAction moveTo-powered obstacle which is moving towards it, it makes small, almost unnoticable lags. I tried lowering the friction and the density of the objects, but nothing helped. Any ideas?
You have chosen to use a circle with phycsicsBody. An SKPhysicsBody object is used to add physics simulation to a node. When a scene processes a new frame, it performs physics calculations on physics bodies attached to nodes in the scene. These calculations include gravity, friction, and collisions with other bodies. After the scene completes these calculations, it updates the positions and orientations of the node objects.
You have also chosen to use SKActions, when using the actions to move a body such changes don't go through the physics engine, indeed usually you could add unwanted actions and unexpected events as "bouncy lags".
So, if you're using physics to move a body, you shouldn't use move actions, apply an impulse or force, or set it's velocity directly
Setting restitution to zero may help. This controls the elasticity, or bounciness of a sprite.
I have a sphere build from multiple objects. What I want to do is when I touch/click an object, that object should find all adjunctive objects. But because none off them are moving, no collision detection can be used.
I can't find a way to detect these adjunctive objects even when the colliders do collide with each other, as I can see that in the scene. I tried all the possibilities, but none off them are working, because no objects are moving.
Is there a way to check for manual collision detection, or is there some sort of way to let Unity3d do the collision detection automatically?
You could keep a list of all those objects, then when your event happens you can send messages to all them to do what you want them to do.
Lets assume you want your sphere to break into little pieces. You send a Force message to the sphere. Then you use Newton's Laws of motion and find out how much velocity each piece gets. Remember velocity is a vector thus it has direction.
This is how I would do it and still keep the right amount of control over what happens in my game/simulation. Remember F = ma.
you could use RaycastHit (http://docs.unity3d.com/Documentation/ScriptReference/RaycastHit.html) for your collision, this also works on non-moving objects but it needs more performance
You can add rigidbody to every objects; when you touch one of them, give a force onto it, then it is going to move and trigger event of the adjacent objects.
for the reason you do not want to move the object you touch, you can cancel movement in the OnCollider or OnTrigger event handler function.
I managed to work around this by checking the distance from the selected object and all other objects that are part of the sphere. If the distance is below a certain value, then it is an adjunctive object.
Although this is certaintly not fool proof, it works without problems so far.
I am sorry I was not clear enough. Thanks for all the advice what so ever.