orient particle to specific axis: Page 2

orient particle to specific axis

DJM

i thought id only needed the hitnormal vector. i dont know what to pass to "lookat" and "hitnormal" vector. specific sympton is that theres' is no particle visible right now when spawning the decal

xyz

@DJM said: i dont know what to pass to "lookat" and "hitnormal" vector.

Me neither, because I don't know how your system is set up :)

For lookat you need to send camera look direction, which is camera global basis.z For hitNormal you need to send that forward direction you wanted the particle to stretch along in the first place. If your script already orients "impactnormal" scene (somewhere, somehow) then we'll need to see this code to figure out the correct vector. Assuming "imapactnormal" is already oriented so that forward axis is its local z axis then the whole thing would go as follows:

# get camera node
var cam = get_tree().get_root().get_camera()
# get camera look direction
var lookat = cam.global_transform.basis.z.normalized()
# set look direction to shader
particles.process_material.set_shader_param("lookat", lookat )
# assuming the forward direction is our current local z axis, send it to shader
var hitNormal = global_transform.basis.z.normalized()
particles.process_material.set_shader_param("hitNormal", hitNormal)

Note that camera lookat needs to be sent every frame, because it changes as you rotate the camera. So this code should go into _process()

DJM

im using code from a tutorial on the net to spawn a simple quad with a texture im not sure if its the best way , cause it doesnt seem to allign the quad decal at the facing normal always correctly. i ve found this guys' tutorials dont always seem to be designed very well, but it was the first thing i had found

xyz

The code calls look_at() at the end. This aligns impact's global z axis with collision normal, as assumed. So code in my previous post should work. If you don't see anything, try to use reversed hitNormal or lookat vector to flip the billboard facing. You got this.

DJM

@xyz how do i get the MainCamera that is a child of the players' node? im using a 2 camera setup so i think the code doesnt get the correct cam variable

xyz

You get it the same way you get any other node, by using get_node(relative_path_string)

However addressing nodes from an instanced scene that are "above it" in the hierarchy is considered a poor practice. It can lead to future bugs (e.g. if instanced scene assumes certain node configuration in the parent scene that changed in the meantime)

Best approach would be to define a property in the instanced scene that's supposed to hold the reference, and then inject its value upon instancing from the scrip that instanced it. In impactnormal:

var cam = null

in RayCast.firebullet():

impact.cam = $"../"

Now impactnormal has the reference to the camera

DJM

i get "invalid on base NIL" error in the decal script

raycast script

extends RayCast

export(PackedScene) var impact_normal
export var force = 20.0
export var damage = 50.0
export (NodePath) var maincamera_path
onready var maincam = get_node(maincamera_path)
func firebullet():
	self.force_raycast_update()
	
	if self.is_colliding():
		var collider = self.get_collider()
		
		var impact = impact_normal.instance()
		collider.add_child(impact)
		if collider is RigidBody:
			
			collider.apply_impulse( self.get_collision_point() - collider.transform.origin ,- self.global_transform.basis.z * force)
			
		impact.cam = maincam
		impact.global_transform.origin = self.get_collision_point()
		impact.look_at(self.get_collision_point()+ self.get_collision_normal(),Vector3.UP)

decal script

extends Spatial



export (AudioStreamSample) var impactsound 
export(NodePath) var particles_path
export(NodePath) var myaudio_path
onready var particles = get_node(particles_path)
onready var myAudio = get_node(myaudio_path)
var cam = null

var random = RandomNumberGenerator.new()

func _ready():
	
	#add_to_group("ignore")
	random.randomize()
	addDecal()

func addDecal():
	myAudio.stream = impactsound
	myAudio.pitch_scale = random.randf_range(0.9, 1.1)
	if myAudio.playing  == false:
		myAudio.play()
	
	
	
func _process(delta):
	
	
	# get camera look direction
	var lookat = cam.global_transform.basis.z.normalized()
	# set look direction to shader
	particles.process_material.set_shader_param("lookat", lookat )
	# assuming the forward direction is our current local z axis, send it to shader
	var hitNormal = global_transform.basis.z.normalized()
	particles.process_material.set_shader_param("hitNormal", hitNormal)
	particles.set_one_shot(true)
	particles.set_emitting(true)
	
	

func _on_VisibilityNotifier_camera_exited(camera):
	self.queue_free()

xyz

A good way to debug when you get null reference errors is to print the value every step of the way. Printing is the first line of defense in debugging. When you post error messages, please paste the full message and line it happened at. Otherwise we can't tell which variable at which moment the editor is complaining.

My first suggestion would be to try to assign impact.cam before adding impact as a child. Not that when you call add_child() the code in child's _ready() callback will be executed. So if at this point something isn't initialized, the error might happen.

print(maincam.name) #make sure maincam is ok
impact.cam = maincam 
collider.add_child(impact)

DJM

error happens at startup of sceneµat this line

var lookat = cam.global_transform.basis.z.normalized()

tried setting impactcam before addchild, same error print "maincam.name" doesnt get called

guess ill be using a 3d spritesheet instead seems less complicated for the same effect. would have been nice to spawn particles in a stretched billboard that spread a little to really have that impact effect at the normalvector for lets say an explosion or something

xyz

Then there's something wrong with getting the camera node in this line

onready var maincam = get_node(maincamera_path)

Check if maincamera_path is correct. Print it out in RayCast._ready(). Always print everything you suspect may be related to the problem.

To billboard a sprite in the same way, you'll need to attain exactly the same two vectors: camera look direction and alignment normal. Only difference would be that the basis calculation is now done in script instead of shader.

DJM

prints out the correct path

ill leave it for now, giving me a headache

cybereality

You need to make sure cam is valid, as I believe process may run while it is still null. An easy way to fix it is to check make sure cam is valid before running any of the code in process():

func _process(delta):
    if cam:
        var lookat = cam.global_transform.basis.z.normalized()
        # rest of code on this level

xyz

Then the problem is that RayCast.firebullet() somehow gets called before RayCast._ready().

When/if you get back to this, try to assign maincam at the start of firebullet():

maincam = get_node(maincamera_path)

cybereality

The cam is not being set on ready. It's being manually assigned after the instance is created.

cybereality

Or move the code like this, since I don't think _process will happen until the object is in the tree.

var impact = impact_normal.instance()
impact.cam = maincam
collider.add_child(impact)

xyz

@cybereality said: The cam is not being set on ready. It's being manually assigned after the instance is created.

maincam is assigned on ready, from the path set via gui, Then cam is assigned from maincam. But it looks like maincam is still null when first assigned to cam from within firebullet(). But we don't know who and when called firebullet() :/

Not sure why @DJM gave up now. This should be easily fixable. Its order of execution/initialization problem. Ultimately you can just attain and assign everything that is needed right before impact is added to the tree, not relying on any uncertain previous initialization.

cybereality

No, maincam is valid. cam is the problem. maincam is set on ready in RayCast node and should be valid (provided it was linked in the inspector, which I assume it was, but good to double check). I believe the issue is that cam in the decal Spatial is initially set to null. It is only set to maincam after it is initialized and added to the tree, and the first time it enters _process() cam is null because it has not been set yet. So you either check for null (and allow process to continue on the second frame) or assign cam to maincam immediately after instancing it (before adding it to the tree).

xyz

Right. I suggested printing maincam before adding the decal to the tree. Apparently, as reported by @DJM this print didn't get called at all because the null reference (cam) error in decal's process() stopped the execution. This would mean that decal's process() got called before the decal was added to the tree. Which is impossible with order of calls we both suggested.

Maybe somebody just need to sleep on it and return with a fresh mind :)

DJM

@xyz said: Right. I suggested printing maincam before adding the decal to the tree. Apparently, as reported by @DJM this print didn't get called at all because the null reference (cam) error in decal's process() stopped the execution. This would mean that decals's process() got called before the decal was added to the tree. Which is impossible with order of calls we both suggested.

Maybe somebody just need to sleep on it and return with a fresh mind :)

yeah i have no idea why it tries to get the cam even if its not even instantiated yet

xyz

Maybe there's a decal scene instance manually put somewhere in the main scene

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