(unsolved) How to render primitives/draw_* to a texture ?

[marsh vault]

Hi, i'm making a 2D game with 100% vectorial graphics to accommodate to all screen resolutions but because they take a lot of time to render them every frames i wanted to render then to a texture, save them in memory then display the texture instead of the vectors but i still can't find how to render a draw method on an empty image file

Also i'm on Godot 4.4d7 if it's useful 👍

[azure solstice]

Image.load_svg_from_buffer() should be what you're looking for.

[marsh vault]

no i'm using draw functions and i want to render them on an image that you save as a .png instead of rendering it to the screen

but thank you i didn't know that you could load SVG, it might be useful for me for other games

[azure solstice]

then you could use a subviewport to render the primitives to it and and the use get_texture() to recieve the last frame of it.

[marsh vault]

So it would work like this ?
view = SubViewport.new()
view.draw_circle(???, ???, ???, ...)
view.get_texture().get_image().save_png("path...")

[azure solstice]

no, subviewport is a node and it has to be part of the scene tree. you put the nodes you want to render as its children, wait a frame and then do get_texture().
you also might have to adjust some settings so it works without needing to actually be rendered to the screen.

[marsh vault]

I just did that but i just get a black screen

i can wait 0, 1 or 10 frames but i still get a pitch black image instead of a transparent one with the object draw on it

what do i do is when i have 6 objects to render, i do an array of 6 dictionaries (subviewport; node; path) and a timer

the first pass (timer = 0),
spawn a SubViewport node as the subviewport key's value,
then spawn a node2D node as the node key's value,
set the (relative) path name as the path key's value,
set the node2D node as the child of the SubViewport node,
then render on the node2D

after that i raise the timer by one, wait another frame then

the second pass (timer = 1),
get the texture, image, then save_png of each viewports
then delete all node2D and subviewport nodes

[azure solstice]

okay to start it would probably be simplest to just put the Subviewport inside a Viewportcontainer. that way it should definetly render with its default settings.

[marsh vault]

I've tried both "one container per subviewport" and "one container for all subviewports" and nothing has changed, sorry i'm not good with viewports 😅

[marsh vault]

(unsolved）How to render primitives/draw_* to a texture ?

(unsolved) How to render primitives/draw_* to a texture ?

[azure solstice]

the subviewportcontainer would only affect a single subviewport. But if you set SubViewport.render_target_update_mode to UPDATE_ALWAYS it should also work without containers. Alternatively UPDATE_ONCE can be used if you only want to render the next frame.

[marsh vault]

Yes i've tried this and when i use get_viewport() it does save the main viewport image (so the problem isn't at the saving step) but what ever i do, i can change every settings but i still can't use the draw functions on them (Viewport or Node2D) it's just a black screen 🤷‍♂️

[azure solstice]

hm, could you show your code?

[marsh vault]

ok ! i'm essencially doing this (it's a simplified version, in the normal version i'm rendering 17 different notes with a pipeline made for that and it's almost 1000 lines long)
`
var pass = 0
var size: float = 88.
var subv := SubViewport.new()
var nd2d := Node2D.new()

func _ready():
subv.add_child(nd2d)
subv.set_disable_3d(true)
subv.set_transparent_background(true)
subv.set_size(Vector2i(size, size))

func _process():
queue_redraw()

func _draw():
if pass == 0:
draw_note_A(nd2d, Vector2(size, size) / 2., size)
if pass == 1:
subv.get_texture().get_image().save_png("a_note.png")

func draw_note_A(node:Node2D, position:=Vector2(0, 0), size:= 1.):
node.draw_circle(position, size, Color.WHITE, true, -1.0, gl.win.aa)
node.draw_circle(position, size * 0.9375, Color.WHITE, false, size * .125, gl.win.aa)
var sVze = Vector2(size, size) * 56./128.
var sAze = Vector2(size,-size) * 56./128.
node.draw_line(position-sVze, position+sVze, Color.WHITE, size/(5.7)*sqrt(2), gl.win.aa)
node.draw_line(position-sAze, position+sAze, Color.WHITE, size/(5.7)*sqrt(2), gl.win.aa)`

It just doesn't draw to the viewport and i have no idea why

[iron basin]

You're never calling your draw method?
Also subv seems to never be added to the tree.

[azure solstice]

oh right isn't is _draw()?

[azure solstice]

you have to use _draw()

draw() is the signal that gets emitted on a redraw

[marsh vault]

i did, i just forgot to rewrite the "_" in the discord message

[azure solstice]

oh my bad

[marsh vault]

it's not automatically added to the main scene ? and yes in the full one i'm calling draw in the process function this is just the essentials

[azure solstice]

add_child() exists for a reason

also if you want to draw the node this script is attached to, it's not ideal to create the viewport here, as it needs to be a child of it.

also also, you can't draw on a different node inside _draw() as far as i know.

[marsh vault]

well, i have my main control node with nothing else manually added in the scenetree, and i do everything by code (i come from game maker studio sorry if i don't get the node system very well)

[iron basin]

Of course it's not, after var subv := SubViewport.new() the subv is parentless.

[azure solstice]

well you are pretty ambitious for someone just starting out.

[marsh vault]

i first did my project in game maker but because i couldn't use thread i did it in C, but SDL was a bit glitchy (and it's quite time consuming to do big projects in C) so i used Godot

But i've been making games for quite some time, this is just the node system that i don't really get

[azure solstice]

well i would suggest to first learn how to properly use the systems godot has to offer, like the node system.

[marsh vault]

Ok i'll try adding subv to the main scene and i'll see if it'll work

[azure solstice]

also like i said, _draw() allows you to use the draw-methods for this node. node.draw_circle() won't work.

[marsh vault]

i did that because in the function to draw the note is not in the same node but in the art autoload node (where all the code to draw the vector sprites are) so i have to pass the node i'm using to draw on the right node and not on the art node

[azure solstice]

well in that case you can pass the whole node that's supposed to be drawn, using change_parent() reparent(), or just add_child() if the node doesn't have a parent yet.

although reparent is more intended for changing a parent while keeping the position, so i would suggest sticking to remove/add child.

[iron basin]

If you want to draw with/using a different node (CanvasItem) then you can connect to its draw signal and use such other CanvasItem for drawing. Something like:

  (...)
  other_node.draw.connect(draw_something.bind(other_node))

(...)

func draw_something(drawer: CanvasItem) -> void:
  drawer.draw_circle(...)
  ...

[azure solstice]

oh didn't know that's possible. good to know!

[marsh vault]

So "other_node" should be nd2d (the node 2D in the subviewport) and draw_something is draw_note_A(...) ?

but in that case i should use a CanvasItem alone and draw on it instead of a SubViewport and a Node2D ?

[iron basin]

Technically you could use RenderingServer methods to add draw commands for any canvas item from anywhere. The thing is before NOTIFICATION_DRAW, draw signal, and _draw method such drawing commands are cleared, so you'd need to be careful about synchronizing it properly. CanvasItem.draw_... methods are restricted to be called only within this specific chunk because of that. https://github.com/godotengine/godot/blob/da4f9339ea7f614f5965e6a6b918b8c8285f2e1d/scene/main/canvas_item.cpp#L139-L149

[iron basin]

If I get your code right, yeah, something like that. But nd2d would of course also need to be within the SceneTree (soemwhere within your SubViewport? ).

[marsh vault]

it already a child of the viewport, but then i tried making the viewport the child of the current scene and it didn't changed anything 😅

[marsh vault]

I'm getting to this

nd2d.draw.connect(gl.gp.tex.note.bind(nd2d).call(nd2d, pos, 2, size, 1))

which looks very convoluted and crashes lmao

i'm going to try with a mock-up function, maybe ".bind" can't handle functions in dictionaries

[iron basin]

No idea about your specific details, but I doubt you're returning a Callable (like a method) from gl.gp.tex.note (you're calling its "version with bind").
(you can't connect anything else than a Callable to a signal)

[marsh vault]

before i was using

gl.gp.tex.note.call(nd2d, pos, 2, size, 1)

gl = global autoload
gp = gameplay dictionary
tex = texture dictionary (it's the vector data)
note = the function to draw a note

nd2d = node to draw to (: Node2D)
pos = position (: Vector2)
2 = note type (no written types)
size = well.... the size (: float)
1 = alpha (: float)

[iron basin]

You don't want .call(nd2d, pos, 2, size, 1)

[iron basin]

Guessing you might want nd2d.draw.connect(gl.gp.tex.note.bind(nd2d, pos, 2, size, 1))

[marsh vault]

then how to i pass arguments to my function ? it's the only way i've found it pass arguments to a function in a dictionary

[marsh vault]

ok thank you i'll try !!

[iron basin]

That's assuming gl.gp.tex.note takes relevant arguments.

[marsh vault]

it does, it displays correctly when i have 'self' for the Node2D argument

[marsh vault]

i'm still getting a black image when i'm saving it 😅

[iron basin]

Tons of potential causes. E.g. you could be saving it too early, see: https://docs.godotengine.org/en/4.3/classes/class_renderingserver.html#signals.
E.g. this should ensure the whole frame was drawn:

...
await RenderingServer.frame_pre_draw
await RenderingServer.frame_post_draw
...

[marsh vault]

Still doesn't change anything (it freezes for 1 frame before saving but that's it)

i think i'll do an empty project and try doing a basic subviewport off-screen rendering system then if i manage to get it to work i'll back port it into the main game