I have a node with a cube attached which represents for example a door. The physicsbody type is .static. If i animate the node up, rotate it and animate it down to the orignial position of the physicsbody stays in the upper position.
In the debug mode the color of the phyisicsbody is first grey (i asume grey = .static), after the translation up, the physicsbody stays at the bottom. As soon as I rotate the node in the upper position, the physicsbody becomes green and moves up to the nodes position. After I translate the node down to the original position, the physicsbody stays in the upper position. Why is this behaviour? Is this because the type is .static?
I know if I set the physicsbody type to .kinematic (shown red in debug) mode it works as expected. The physicsbody adapts the translations and rotations. But with .static type I can place more objects before the fps drops than with .dynamic.
From the documentation for SCNPhysicsBodyTypeStatic we learn that it is
A physics body that is unaffected by forces or collisions and cannot move
However you can use resetTransform to explicitly tell the engine that the node has moved and that the physics body needs to be updated:
If you change the position or orientation of a node with an attached
static or dynamic physics body, call this method afterward to ensure
that the physics simulation incorporates the change. You need not call
this method for kinematic bodies.
Note that dynamic and physics bodies
are designed to be moved only by the physics simulation or not at all.
You may use this method to move them regardless of this restriction,
but at a cost to performance.
Related
I am creating a tilemap platform game in SpriteKit. I assigned collision paths to the physics body of all ground tiles and made them non-dynamic. To the player I assigned two collision polygons: a circle on the bottom and a rectangle on the top.
The player sprite has a fixed position on screen, while the level is scrolling from right to left. Now, as long as the player sprite is on flat ground, the collisions work perfectly and the player is walking on the ground. However, I also have some sloped terrain tiles that I want the player to follow (e.g. walking uphill). But when the player reaches a sloped tile, he simply bounces off of it, being unable to "climb" it.
Similarly, when I drop the player from above on a sloped tile, he slides down the "hill", instead of remaining in position.
I have both restitution and friction set to 0.
So how can I make the player sprite follow the ground regardless of its shape and how can I make the player stay on a sloped tile instead of sliding down?
I tried using SKConstraints with positionX set to a constant value. At first it seemed to work, but then the player got stuck in the middle of a sloped tile and eventually fell through it.
I also tried different shapes of collision polygons on the player (e.g. a rectangle instead of a circle at the bottom) but that changed nothing.
Any help is appreciated!
This has more to do with your game logic instead of your map properties. You need to have several "states" for your player. For example, if your player is idle you can set the CGVector to 0,0. This will stop the player from moving in any direction.
To give you some examples on movement. Let's say you want to make your object move right:
// move node's physics body to the right while leaving vertical movement as is
// 160 is just an example
myNode.physicsBody.velocity = CGVectorMake(160, self.physicsBody.velocity.dy);
// do not allow right movement to exceed 160
if(myNode.physicsBody.velocity.dx > 160)
myNode.physicsBody.velocity = CGVectorMake(160, self.physicsBody.velocity.dy);
To move left you inverse the dx value:
myNode.physicsBody.velocity = CGVectorMake(-160, self.physicsBody.velocity.dy);
if(myNode.physicsBody.velocity.dx < -160)
myNode.physicsBody.velocity = CGVectorMake(-160, self.physicsBody.velocity.dy);
Allow myNode to be affected by gravity and it should remain in contact with the ground as it moves down a slope.
It's a tilemap platform game...
Then gravity isn't important, put gravity to a very low value and then change all your impulses for the jumps and such in relation to the change in gravity...
OR,
Possibly, if the game isn't randomly generated you can set up a uibezierpath, and turn the path off if he stops moving up the hill.
But then if he stopped mid-hill or was starting from the top, he would still slide down...
And increasing friction (not setting it to 0) may help. Try friction at 1?
Hello I have a physics body created within sprite kit editor, here are the settings I've set for it:
The problem is, it isn't acting "static". If another physics body bumps into it "weirdly" (for lack of a better description) it often glitches, flying all over the screen, or when I had it pinned, rotating around the pinned location. -Shouldn't this act static and never move, unless it is explicitly moved in code? I need it to have an alpha mask physics body and stand completely still (it is the ground in my scene).
I have a SceneKit setup and have one Sphere in it that is setup as a Dynamic body.
I am able to run the app and see the sphere drop on the static body floor.
What I am trying to do is setup the scene so the sfere initially does not drop.
Then when a function is run I want the sfere to drop.
what is the correct logic / steps to make the scene suddenly (maybe when a button is pressed or something) drop the sphere?
I have tried also to set the sphere to mass 0 and then set the mass to 100 but it does not cause the drop...
Mass doesn't control how fast something falls. This is true in the real world, but more so in simulations that take shortcuts instead of simulating every detail of real-world physics. (Sadly, iOS devices still don't have the CPU power to account for the rotating reference frame of the Earth, the Van der Waals attraction between your sphere and any body especially close to it, the strong force that keeps its triangles atoms together, etc etc.) In SceneKit, gravity is just a constant acceleration in a specific direction.
Setting mass to zero and switching it to something else interferes with the distinction between static/kinematic and dynamic bodies... so don't do that.
As #mnuages notes, you can add/remove the physics body from your sphere when you want it to be affected or unaffected by physics entirely.
But what if you want to keep the sphere's physics body for other reasons—such as allowing other bodies to collide with it even before you make it start falling? There are a few approaches you could use for that:
Set the sphere body's damping to 1.0.
Set the sphere body's velocityFactor to zero (at least in the direction of gravity).
Both of those will keep the sphere from moving when something else hits it. If you want the ball to get knocked around, but not be affected by gravity, the best thing to do might be to switch out scene gravity for physics fields:
Set scene.physicsWorld.gravity to SCNVector3Zero.
Add a SCNPhysicsField created with the linearGravityField constructor to your scene, and set its direction and strength to get the kind of gravity behavior you want.
Set the categoryBitMasks on both your sphere body and the gravity field such that the field affects other bodies but not the sphere.
Whichever of these methods you use, you can change them when you want to "turn gravity on" for the sphere: reduce the damping, reset the velocityFactor, or change the sphere's or the gravity field's categoryBitMask.
As of iOS 9, you can set the isAffectedByGravity property to false then flip the value to true to make the sphere drop: https://developer.apple.com/reference/scenekit/scnphysicsbody/1514738-isaffectedbygravity
setting a physics body to sphere only when you want to it to be affected by gravity should work.
I currently have a scene which contains a central node at the root of the scene with earth-like geometry and a node representing a flying vehicle.
However I cannot find the right approach to control the movement of the vehicle. I need the ability to turn left and right while orbiting at a static altitude and speed.
I have tried many combinations of animations and physics body forces all leading to undesirable results.
The closest I've come is:
Setting the pivot property of the vehicle to the centre of the scene
Then setting an Action like below to control moving forward
[_vehicleNode runAction:[SCNAction repeatActionForever:[SCNAction rotateByX:-1 y:0 z:0 duration:10.0]]];
Then finally applying forces for turning left and right with
[_vehicleNode.physicsBody applyTorque:SCNVector4Make(0, 1, 0, 1) impulse:YES];
However I cannot seem to set the pivot and/or position to the right value to get the desired result.
Edit: It appears as the above method would be the solution I'm looking for, however for some reason when I add geometry to the vehicle node, it's position in the scene graph gets changed dramatically. When I add hardcoded buttons to change it's position to where it belongs it appears correct for only that single frame then straight back to being in the middle of nowhere.
Edit 2: After replacing all geometry with a primitive sphere for testing the node is now rotating as intended but is now unaffected by physics forces appearing to ignore it's declaration as a dynamicBody.
If I understand what you are trying to achieve correctly, you can try this:
add a first node to your scene, positioned at (0,0,0) and make it rotate forever along the Y axis using an SCNAction
add your ship node as a child of the first node. Position it at (X,0,0) so that it orbits around the earth
rotate your ship node along the X axis with an action or an animation
I'm working on a game in which the user should be able to trigger 'rods' that come out from the edge of the screen to displace elements on screen (balls). These projectiles roughly resemble pool-cues. Or perhaps pinball plungers, except that they start from the 'loaded' position (mostly offscreen), and when triggered, they eject out, then quickly retreat.
I'm unclear how I should build these with Sprite Kit.
The game uses the PhysicsEngine, and the onscreen balls should be effected both by gravity AND they should be displaced when they collide with the rods. However the rods should neither be effected by gravity, not displaced when they collide with the balls -- they should simply retreat regardless of whether they've made contact with the balls.
I realize I can set the affectedByGravity property for the rods. However because they will still displace slightly when they collide with the balls. How can I 'fix' or 'peg' them in place? Do I need to use an SKPhysicsSlidingJoint? If so, has anyone encountered any examples online? Is there a simpler way to do this?
A related physics engine, Box2D distinguishes static, kinematic, and dynamic bodies.
Kinematic bodies can move and will collide with other objects, but they are themselves not affected by dynamic bodies or forces like gravity. Thus, consider setting rod.dynamic = NO; but animate it with actions. See also here in the reference for SKPhysicsBody.