I'm working on a project using Andengine GLES2-Anchorcenter
I have a dynamic body and I want to make it move around a circle like earth moving around the sun !
the problem with angular velocity that it rotates around it's center , I want to rotate it around the center of the circle ?
I tried many ways , I tried joints and more but It didn't work
can anyone help !
Move the body along the (circular) path using setVelocity so that every step the body moves further on the path. (You have to calculate the needed velocity to reach a certain point). It's actually quite easy: sqrt((destination.x - position.x)^2 + (destination.y - position.y)^2) / timestep. You should avoid using setTransform which will break the physical behaviour... Any luck?
Related
I am getting started with Unity and am just trying to get my head around the units. What are these units? It seems they are their own 'quantity' and to treat 2 units as 2 times the value of 1 unit.
Anyway - I am trying to workout how to optimally calculate transforms to objects sit exactly where I want them to.
In my scene I have a terrain and a cylinder as so:
As you can see my cylinder is floating. I want the cylinder to sit perfectly on top of the terrain.
My terrain is at the following transform: 0,0,0 and scale 0,0,0 (not sure how to tell it's dimensions yet).
My cylinder is part of a new object, as so:
My FirstPersonPlayer is at transform: 85.9,2.165,51.8 and scale 1,1,1. My Cylinder is at 'localposition' 0,0,0 and local scale 1.2,1.8,1.2
Now - the transform of FirstPersonPlayer on the y axis appears to be what I need to correct.
Currently it is set to 2.165 and is floating a bit above the terrain.
Through manually shifting it, around 1.85 looks about right - but I want to know how to calculate that, rather than doing a finger in the air 'that looks about right'.
Can anyone help me? (Before you suggest using gravity etc , I actually am, but don't want the player falling as soon as they start, however slight that may look or feel.
Many thanks,
As per #Nikola Dimitroff the answer is:
You don't have to compute anything, hold Shift + Control and drag the object. Every game engine ever made calls this "Snap to Ground"
I appreciate and agree with the other comments.
I downloaded a bullet model from TurboSquid.
But the bullet is pointing to the left (negtive X axis).
So the whole thing needed to be turned 90 degree on Y axis to face "forward" (Z axis).
I'm making a first-person shooting game so I needed the bullet to face exactly where the camera was facing.
So if I simply set
bullet.gameObject.transform.rotation = Camera.main.transform.rotation;
The bullet will just facing "left"!
I tried to do a additional rotation after the rotation assignment as follow:
bullet.gameObject.transform.Rotate(Camera.main.transform.up,90);
It worked fine if the view is parallel to the horizon.
But it will started to facing some weird ways if you're shooting up or down!
I also tried to create an empty parent GameObject and throw the bullet in as its child, and set the parent's rotation.
Now it "always" facing "forward" (Z axis)! No matter where I turned my camera!
Could somebody please be so kind and teach me how to fix this!?
Much appreciated!
Wrap your model in a parent object, like this:
Then you can rotate the BulletModel 90 degrees and attach the script that moves the object to the ParentBullet. This should do the trick.
It's usually considered good practice overall to separate your model and logic/actual object like this.
I fixed it by some weird ways!
I just set its forward to the camera's right, and its right to the camera's back.
bullet.gameObject.transform.forward = Camera.main.transform.right;
bullet.gameObject.transform.right = -Camera.main.transform.forward;
But I still don't know why the empty parent GameObject trick don't work!?
I have a physics body that gets hit and rotates a lot. I want to limit the amount it can rotate (only 45 degrees in each direction or something) and I wanted to try to do that by applying torque if the direction goes past a certain point. I'm ok with the sprite wobbling back and forth (it's a bird).
I'm open to other suggestions on how to limit the rotation as well.
Thanks in advance!
Edit: I've already tried using zRotation (I printed it out and it was always 0.) I also tried using the vector but that gave me the direction the sprite was going.
xcode 5 iOS7 sprite kit.
My wish is to make a sprite that has its own gravity.
Like a planet. If another sprite comes within a certain range of it, it will slowly pull the other sprite closer.
I have two sprites. One moving and one stationary. When the moving sprite gets in a given distance of the stationary sprite the stationary sprite gravity should slowly pull the other sprite towards it. This way the moving sprite would change its path in a soft curve.
My idea would be to calculate the distance from the stationary object to any other object and if close enough start pulling and if the moving object gets out of range ageing, then stop pulling.
Would probably need to research some vector calculation.
Thats my immediate thoughts.
Is this possible and how? Does it already exist?
A friend of mine did this for his physics dissertation. multibody gravity simulation. So yeah you can but you need to be willing to learn some maths. Apparently there is a clever optimisation to make it run decently nlog(n) rather than n^2). you probably want to ask this on the physics version of stack overflow to get a good answer. I have the code at home ... will post it later but you will want an explanation - i used it in an xna app. Its badass once you get it working - although if you want naturally orbiting objects then you will want to code them using parametric equations for easy and cool orbits. Simply because its hard to solve and with time even using double will result in some errors (the good implementations also work out the error and adjust - again will post later). But the real problem is solving for stable orbits. You then use the algorithm for free moving bodies such and player objects / npcs. Although solving accurate movement for npc in a changing field is v hard.
you want to look at this question: Jon Purdys answer is the one you want
multi body physics - gravity
and this one (which is linked from above) ...
https://gamedev.stackexchange.com/a/19404
There is not a dead-simple way of doing that in any platform as far as I know maybe except for some game engines/platforms that export for different platforms (cocos2d, construct 2 etc).
What you need is a physics engine whether you write one (which is a complicated but fun thing to do) or use an available one.
Luckily I've found a link describing the usage of the famous 2D physics engine "Box2D" on iOS.
This one explains how you can include Box2D in an openGL application (but you can apply this to other environments (sprite kit) I think altough I'm not an iOS guy);
http://www.iforce2d.net/b2dtut/setup-ios
Anyways, you now know what to look for...
For iOS 8.0+ : you have SKFieldNode : radialGravityField()
For iOS 8.0- : one solution could be : 3 to 9
add your sprite ( planet ) with its physics
add an invisible SKNode ( the gravity zone ) with its own physics, as a child of your sprite, but with a radius much more than your sprite's one
you have a little explanation about invisible node here : https://developer.apple.com/documentation/spritekit/skphysicsworld
both, your sprite and the invisible node are centered in a zero gravity world
we look for contact and not collision ( set correctly your bit masks )
when any object get in contact with the invisible node ( gravity zone ), first you remove any moving action or impulse from it and then we add to this object an SKAction to move it toward the center of your sprite ( planet )
at second contact between this object and your sprite ( planet ), you remove all actions again from the object with a velocity = zero
I am trying to make a snake kind of game on the iPhone. For that I plan to have a simple dot as the sprite which draws a line. The dot is controlled by two buttons on the left and the right of the screen enabling it to turn left or right. Now I really do not have any idea how to make the sprite move automatically forward and how to program the turning. It should not be exactly as in snake where it abruptly turns left or right but it should more be a smooth curve. I hope you're getting my point and I'd appreciate all kinds of thoughts! Thanks a lot!
Somewhat trying to make it like this:
http://www.bnet.im/images/screen_curve.png
There are a lot of ways of doing this, but one simple way would be to store the angle of the snake's trajectory (I've called it theta) and move it a fixed amount in every call to Update.
Assuming that the snake class inherits from CCNode:
-(void)Update:(ccTime)dt {
self.position = ccp(self.position.x + cos(theta)*dt,
self.position.y + sin(theta)*dt);
}
You could then update theta from your event handling logic by increasing it or decreasing it when the user taps to turn left or right.