Find out when SCNNode disappears from SCNScene - objective-c

Does a particular method get called when an SCNNode is removed from the scene?
-(void)removeFromParentNode;
Does not get called on the SCNNode object.
To set the scene
I am using gravity to pull down an object. When an object goes too far down, it automatically disappears and the draw calls and polygon counts decrease. So the SCNNode is definitely being destroyed, but is there a way I could hook into the destruction?

Other answers covered this pretty well already, but to go a bit further:
First, your node isn't being removed from the scene — its content is passing outside the camera's viewing frustum, which means SceneKit knows it doesn't need to issue draw calls to the GPU to render it. If you enumerate the child nodes of the scene (or of whatever parent contains the nodes you're talking about), you'll see that they're still there. You lose some of the rendering performance cost because SceneKit doesn't need to issue draw calls for stuff that it knows won't be visible in the frame.
(As noted in Tanguy's answer, this may be because of your zFar setting. Or it may not — it depends which direction the nodes are falling out of camera in.)
But if you keep adding nodes and letting physics drop them off the screen, you'll accumulate a pre-render performance cost, as SceneKit has to walk the scene graph every frame and figure out which nodes it'll need to issue draw calls for. This cost is pretty small for each node, but it could eventually add up to something you don't want to deal with.
And since you want to have something happen when the node falls out of frame anyway, you just need to find a good opportunity to both deal with that and clean up the disappearing node.
So where to do that? Well, you have a few options. As has been noted, you could put something into the render loop to check the visibility of every node on every frame:
- (void)renderer:(id<SCNSceneRenderer>)renderer didSimulatePhysicsAtTime:(NSTimeInterval)time {
if (![renderer isNodeInsideFrustum:myNode withPointOfView:renderer.pointOfView]) {
// it's gone, remove it from scene
}
}
But that's a somewhat expensive check to be running on every frame (remember, you're targeting 30 or 60 fps here). A better way might be to let the physics system help you:
Create a node with an SCNBox geometry that's big enough to "catch" everything that falls off the screen.
Give that node a static physics body, and set up the category and collision bit masks so that your falling nodes will collide with it.
Position that node just outside of the viewing frustum so that your falling objects hit it soon after they fall out of view.
Implement a contact delegate method to destroy the falling nodes:
- (void)physicsWorld:(SCNPhysicsWorld *)world didBeginContact:(SCNPhysicsContact *)contact {
if (/* sort out which node is which */) {
[fallingNode removeFromParentNode];
// ... and do whatever else you want to do when it falls offscreen.
}
}

Your object will disappear if it goes further than the ZFar property of your active camera. (default value is 100.0)
As said by David Rönnqvist in comments, your Node is not destroyed and you can still modify its property.
If you want to hook-up to your Node's geometry disappearance, you can calculate the distance between your active camera and your Node and check it every frame in your rendering loop to trigger an action if it gets higher than 100.
If you want to render your Node at a greater distance, you can just modify the ZFar property of your camera.

Related

Getting Contact Information with Tiles in Godot

Can I somehow get information that the player has touched a specific tile located in the resource (tilemap.res)?
It is necessary to determine which tile it stands on (for example, on land or in water)
It depends on what kind of behavior you're expecting. There's two major ways to do this:
In each individual script that you want to be affected by the tiles, get the tile it's on every time it moves, then run the logic directly from there.
As above, get the tile the unit is on each time it moves, but instead of just running the logic every time, emit a signal whenever the tile changes, and keep the current tile cached so you can check when it's on a new tile; have the TileMap itself attach to the signal, and when it receives the signal, act on the Node2D until it leaves. This is what I'd do.
The exact method to find the tile is TileMap.world_to_map(TileMap.get_cellv(Node2D.position))--you just need to have the Node2D and the TileMap, and you can get both in the same function using the above two methods.
Technically, you could also procedurally add Area2Ds to the tilemap based on the tiles at various positions using TileMap.get_used_cells_by_id, making sure that the ID is the one that has the special behavior, then attaching the TileMap to those areas' body/area_entered and body/area_exited and using that, but spamming a whole lot of Area2Ds isn't necessary when you can check the tile a Node2D is on directly.

No keyframes are visible but the object still moves

I'm using Blender 2.8 and I just have 2 objects: hand and gun and I want to create animations for them. So, for instance, I want to create a simple firing animation. What I do:
1. I create animation for gun
2. I create animation for hand
But if I switch somehow incorrectly I "lose" the first animation I've created. I tried creating fake users and stuff. I just don't get why I select the armature for which I've just created the animation, it plays, but there are no keyframes.
Here's the vid, here's the file.
Ask me questions if you have any.
The movement may be cached in Blender, you may need to reset the movement cache.
Alternatively, you should look at both the Track Controller and Dopesheet(action editor) - the animation may be stored in both.
The movement could be related to parenting ( to an object that is moving )
The movement could also be caused by physics simulation of a rigid body.
Hopefully with the help of the above, you find the problem.
I had the same problem. In the Animation mode (horizontal tabs across the top of the window), click on the object to animate.
The keyframes will appear.
If the object is not selected, the keyframes disappear.
Just leaving this here so that nobody spends 30 minutes trying to work this out, like i just did.

Tearing graphics in SCNView

Hi, I have a SCNView with some nodes, when rotating I get some strange tearing, the nodes on top have a higher rendering order, changing this seems to have no effect.
Is there anything I can do to get rid of the white lines?
It's like it's fighting for position??
as said above, it looks like you're experiencing z-fighting because your colored objects and white object lie in a same plane.
You can avoir this
By slightly offsetting your geometries, but this trick does not work in every situation (the user might notice the gap depending on the point of view)
by changing the renderingOrder of your nodes but don't forget to tweak the writesToDepthBuffer and readsFromDepthBuffer properties of your materials
When use NO.2 solution mnuages introduced:
node.renderingOrder = 100;//Max value to ensure your node render at latest.
//disable deep buffer for rendering
node.firstMaterial.writesToDepthBuffer = NO;
node.firstMaterial.readsFromDepthBuffer = NO;
This is only work for node's geometry locate top hierarchy otherwise will lead to a weird perspective scenario.

Cocos3D - background shown through meshes

I imported the .pod file created from Blender and the blue background is shown through the eyelash and eyebrow meshes. Does anyone know why I'm encountering this?
WITHOUT additional material (looking normal except the root of the hair).
WITH new green material added to her left shoulder, the eyebrow and eyelash began showing the background
This issue is caused by the order in which the nodes are being rendered in your scene.
In the first model, the hair is drawn first, then the skin, then the eyebrows and eyelashes. In the second model, the hair, eyebrows and eyelashes are all drawn before the skin. By the time the skin under the hair or eyelashes is drawn, the depth buffer indicates that something closer to the camera has already been drawn, and the engine doesn't bother rendering those skin pixels. But because the eyelashes, eyebrows and hair all contain transparency, we end up looking right through them onto the backdrop.
This design use of a depth buffer is key to all 3D rendering. It's how the engine knows not to render pixels that are being visually occluded by another object, otherwise all we'd ever see was the last object to be rendered.However, when rendering overlapping objects that contain transparency, it's important to get the rendering order correct, so that more distant objects that are behind closer transparent objects are rendered first.
In Cocos3D, there are several tool available for you to order your transparent objects for rendering:
The first, and primary tool, is the drawingSequencer that is managed by the CC3Scene. You can configure several different types of drawing sequencers. The default sequencer is smart enough to render all opaque objects first, then to render the objects that contain transparency in decreasing order of distance from the camera (rendering farther objects first). This works best for most scenes, and in particular where objects are moving around and can move in front of each other unpredictably. Unfortunately, in your custom CC3Scene initialization code (which you sent me per the question comments), you replaced the default drawing sequencer with one that does not sequence transparent objects based on distance. If you remove that change, everything works properly.
Objects that are not explicitly sequenced by distance (as in part 1 above) are rendered in the order in which they are added to the scene. You can therefore also define rendering order by ensuring that the objects are added to your scene in the order in which you want them rendered. This can work well for static models, such as your first character (if you change it to add the hair after the skin).
CC3Node also has a zOrder property, which allows you to override the rendering order explicitly, so that objects with larger zOrder value are rendered before those with smaller zOrder values. This is useful when you have a static model whose components cannot be added in rendering order, or to temporarily override the rendering order of two transparent objects that might be passing in front of each other. Using the zOrder property does depend on using a drawingSequencer that makes use of it (the default drawing sequencer does).
Finally, you can temporarily turn off depth testing or masking when rendering particular nodes, by setting the shouldDisableDepthTest and shouldDisableDepthMask properties to YES on those nodes.

How to code a random movement in limited area

I have a limited area (screen) populated with a few moving objects (3-20 of them, so it's not like 10.000 :). Those objects should be moving with a constant speed and into random direction. But, there are a few limitation to it:
objects shouldn't exit the area - so if it's close to the edge, it should move away from it
objects shouldn't bump onto each other - so when one is close to another one it should move away (but not get too close to different one).
On the image below I have marked the allowed moves in this situation - for example object D shouldn't move straight up, as it would bring it to the "wall".
What I would like to have is a way to move them (one by one). Is there any simple way to achieve it, without too much calculations?
The density of objects in the area would be rather low.
There are a number of ways you might programmatically enforce your desired behavior, given that you have such a small number of objects. However, I'm going to suggest something slightly different.
What if you ran the whole thing as a physics simulation? For instance, you could set up a Box2D world with no gravity, no friction, and perfectly elastic collisions. You could model your enclosed region and populate it with objects that are proportionally larger than their on-screen counterparts so that the on-screen versions never get too close to each other (because the underlying objects in the physics simulation will collide and change direction before that can happen), and assign each object a random initial position and velocity.
Then all you have to do is step the physics simulation, and map its current state into your UI. All the tricky stuff is handled for you, and the result will probably be more believable/realistic than what you would get by trying to come up with your own movement algorithm (or if you wanted it to appear more random and less believable, you could also just periodically apply a random impulse to a random object to keep things changing unpredictably).
You can use the hitTest: method of UIView
UIView* touchedView=[self.superview hitTest:currentOrigin withEvent:nil];
In This method you have to pass the current origin of the ball and in second argument you can pass nil.
that method will return the view with which the ball is hited.
If there is any hit view you just change the direction of the ball.
for border you can set the condition for the frame of the ball if the ball go out of the boundary just change the direction of the ball.