Can someone tell me what would be the math required for moving around the small ball in the bar(meter) according to the touch motion.... I needed a clear idea on the logic..
The logic depends on how you want to model the interaction between the finger and the ball. Is it moving through a fluid, like a ball bearing? A gravitational field? Do you want it to decelerate as if under the influence of friction from the sides of the bar? Or do you want to simply have the ball track the finger, without fancy damping of the motion?
My point is that the "logic" can be pretty complicated, depending on how you decide to model it. I'd recommend looking for something canned in JavaScript before coding it yourself.
Related
I have a rather simple react-three-fiber setup that includes cannon.js-powered physics. In the scene there is a cup -- which is modelled as a cylinder whose top radius is bigger than the bottom one -- that is placed on a surface.
When I run the code, during the loading screen everything looks fine. But when physics kick in, the cup suddenly "sinks" into the ground. Why is that? I can't make sense of that...
One theory of mine was that the "physics shape" of the cylinder is not identical with the "optical shape" that gets rendered, but even then the movement I observe still doesn't make sense with any reasonable bounding box I can imagine...
Working example: https://codesandbox.io/s/amazing-proskuriakova-4slpq
Physics are finicky and really hard to debug because you're often trying to intuit the effects of an invisible system by its effects on whatever hybrid view you have.
I notice if i bring the mass downn to a more reasonable value, like 5, the object appears to roll around like a sphere or some other shape.. so I think your theory is sound. I don't know off the top of my head what the solution is, but I do know that the only physics engine I "trust" in the js space, except for very simple simulations, is Ammo.js. It's hard to use, but is an emscripten port of a truly amazing AAA quality library. https://threejs.org/examples/?q=phys#physics_ammo_break
I would start by getting a cube and a sphere working.. once you have verified that those work as expected.. ideally using real-ish world scale units, like a 1x1x1 cube, with a mass of 1. Use a texture on the sphere so you know that its rolling like you expect. Once you have verified the simpler primitives work, move onto the more complex geometries.
Best way forward would be to make an issue on the use-cannon GH. That lib and cannon-es are under active maintenance now. Meanwhile, i believe convexpolyhydron can also do it flawlessly, see: https://codesandbox.io/s/r3f-convex-polyhedron-cnm0s
Is there a way to animate wind for certain game objects?
For example, branches of trees should gently move, like there's a breeze in game. Not gameplay, more like a special background effect.
If it's not possible in code, what would be the best way to create proper sprite images?
I see a few options to actually achieve that Wind Effect.
SKFieldNode, It allows you to actually apply physics effects to nodes. And if you want real tree branches that can move based on the physics, you should combine SKFieldNode with SKPhysicsJoint. When you combine those two you can actually create indepedent Branch Nodes to receive some kind of force to simulate a wind effect. To understand what you can do with SKPhysicsJoint, check out this guide. This solution can get really complex and hard to achieve with superficial understanding of SpriteKit Engine, but you can create an amazing effect using it. Personally, I would not recommend if you have deadlines to attend, physics always get buggy if you lose your grasp on what you are doing, you may invest a lot of time trying to achieve this using physics.
Create different animation of your tree responding to wind movement and control which animation frame you should use at that specif case. I Would highly recommend this one, because you will have control over what is going on with you tree and people that play games don't pay that much attention to what is going on with background, altho is a good thing to think about it from the game experience.
Create your tree textures and change the anchor point to be at the place you want the effect to be more effective and responsive. The farthest the coordinate in the node is from the anchor points coordinate, less effect from your SKAction it will get.
Sorry for my English, is not my native language.
So there are lots of squares (about 200-300) in my scene. They are moving a little, and they need not to cover each other. It's pretty hard for a computer to add Rigidbody2D to them. I tried to add BoxCollider2D and Mesh Colliders on each object and code OnCollisionEnter2D in the script, but it just doesn't work. Convex MeshColliders don't work (at 2D, I suppose. why?). So how can I deal with it without using Rigidbody? Is it a wrong way to use Collider2D?
EDIT:
First of all, I'm sorry for my bad english.
Secondary I want to thank all of you for your answers. These are great references and I'll spend much time to go deeper in that.
I've found the answer, it's quadtree. There's a good example/tutorial in this page
"It's pretty hard for a computer to add Rigidbody2D to them." Do you mean it has performance cost?
Rigidbodies are used for detecting collisions. You don't need both of the colliding sides to have a rigidbody. For example if you have 100 squares in your scene as obstacles, you can have collisions if your player object (e.g. a circle as a ball) has Rigidbody component. In this example, the ball needs CircleCollider2D+Rigidbody2D, the obstacles need only BoxCollider2D.
You should use box colliders instead of mesh colliders. By this way, you can gain more performance. And your collider's "Is Trigger" property should be checked. Rigidbody component's "is kinematic" property should be checked too. By this way, all gameobjects in your scene dedect collision each other.
OnTriggerEnter2D() function can help you catch collision detections between gameobjects in your scene.
my question is just about choosing the right approach because i'm not sure about the solution.
i got 3d model in my project, at some point i want to show animated disassembly , the object is made of somthing like 200 pieces.
so animating with keyframe one by one is time consuming.
the animation i'm looking for is like explosion from the center of the object so the parts will just move out of its center.
example image:
what would you do?
what is the best way to manage such task?
I would code it. Maybe I am biased because I am a programmer, but animating it would be a pain.
So I would import the model into Unity3d. Then I would grab all the parts and store them in a list. Once I have the 200 parts then I can do anything I want to them.
I would then proceed to attach rigibodies and box colliders to them all -- this can be done programmatically. Then you can initiate the explosion by adding a velocity to each part. If you want to be fairly realistic and have something that is fairly random you can give each object mass and then use the equation F=ma for the explosion. That is, each part will get different acceleration depending on the mass they have.
I'm using Farseer and XNA on on WP7. I have 2 objects in my game. The first one is a wall generated from a bitmap. The second one is a player controller - in fact it's just a circle object. This circle follows player's finger.
I need a certain behavior - probably it's very basic, but I can't figure out how to google it. It's a collision detection that just wouldn't allow the controller to come into the wall. It shouldn't bounce. It should just try to follow the finger but not enter the wall.
I know it's not hard to implement it on my own, but if I'm using a physics engine and it happens to offer such a functionality it would be a shame not to take advantage of it. :)
you need to use a BoundingBox object, and check collision VS the object (you should create a BoundingSphere wrapping it)
http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series2/Collision_detection.php