multiple nodes failing to launch the same compute shader

[sly sedge]

Hello, is there something to pay attention to when launching multiple nodes that have the same script launching the same compute shader?
i have this situation, and only one of the nodes is launching the shader as expected.

edit: what comes after was an unrelated mistake, please ignore
i don't really understand: only the color of the light seem to be taken into account somehow? 🤔 also the actual position of the node seem to be ignored for some reason.

Joined are images of the result, the part of the code where i feed the parameters to the shader in the process() and the print showing that the input parameters should differ.
Also i get an error telling me a a device is already submitted, which i do not understand as i got that error also on my light_module() node which launches its own shader once per process() and there is only one of it so why is it unhappy?.

[sacred geyser]

I'm assuming that rd is of type RenderingDevice

Are you using the same RenderingDevice for both nodes?

@sly sedge

[sly sedge]

let me check

var rd := RenderingServer.create_local_rendering_device() #create a local rendering device.

i'm doing that in the declaration of the class at the top

so it may be the issue 👀

No, they are different rendering devices

[sacred geyser]

At least I don't see the issue in the code you have posted so far

oh actually

What are these used for?

[sly sedge]

they're used to determinate the center of the set of tiles calculated, they're intended ot be the player coordinates

the shader is an image centered on the player; so it's to center

but even determining why the direction is the same for both lights, it's not normal

and why out of it all, the color of the light works

[sacred geyser]

How is light_angle defined?

also would love to get the full script that you took that screenshot out of

[sly sedge]

maybe a hint, if i don't do what i do in the ready() at line 61, the color is the same as the first light

[sacred geyser]

Could you just upload the script as a file? 😅

[sly sedge]

sure

[sacred geyser]

Sending screenshots of code is not the best practice ^^

[sly sedge]

just a ctrl c ctrl v and sending it as a txt?

[sacred geyser]

That will work!

[sacred geyser]

Do you get any warnings/errors about duplicate UIDs anywhere?

[sly sedge]

only the error i sent in the first batch of screenshot

i assume it'd be marked in red, i don't see anything UID related int here

i'm thinking it may be cause by the compute list

no nvm

[sly sedge]

ok i'm closing in on the problem i think. I'm rather sure it's because of that error i sent, but i have not found any trace of it online

it seems like the shader just doesn't run for the 2nd light. I had 2 lights because i was grabbing a wrong offset in the shader that mixes everything together

but now i fixed it and surprise surprise, when i look at the input lightmaps, one is empty

So the problem is clearly how to launch both

multiple nodes failing to launch the same compute shader

[sly sedge]

relevant data

the renderingdevice is different, the compute list value isn't but it doesn't seem to be the problem right? idk how you'd even make that vary

[sacred geyser]

I'm thinking that this error happens because you are trying to have the thing calculated every frame

and the thing is not fast enough for that or something

I would imagine that it's not related to the other issue, but you might as well fix that issue as well and hope it somehow magically fixes the other thing :b

[sacred geyser]

What about the array that has the inputs? Do you somehow have the same array referenced between the two nodes?

ACTUALLY that could be possible

I think..?

Exported array -> duplicate node -> same array on both nodes..?

would have to test that to know if that is possible

Doesn't seem to happen

(just tested this)

[sacred geyser]

This is still worth checking, though

[sly sedge]

i rigged the shader to set the first float of the array to be equal to 2, and i'm changing the first byte of the first float right after getting the data from the buffer

and look

one of them is equal to 0, so it means neither the shader nor the output_bytes[0] could modify it, so i guess i have goofed the array declaration somewhere somehow

🤔

[sly sedge]

how do you check the adress of an array in godot? i tried looking for that earlier but didn't find an appropriate method

[sacred geyser]

ah hm

You are probably getting all 0's because the compute shader was not ready yet

[sacred geyser]

^^^

[sly sedge]

yeah i'm not forgetting that error, but shouldn't that output_bytes[0] = 64

still go through

[sacred geyser]

not sure what setting the first byte to 64 would do to a float ngl

[sly sedge]

it's putting that small decimal part in

[sacred geyser]

since you're setting that byte and then converting to a float

[sly sedge]

hmm

[sacred geyser]

Sometimes float formatting does not show all decimals

I mean in different programs and languages and such

not sure what the case is in Godot

[sly sedge]

it shows for the other that's set to 2, so i assume it's not small enough to be ignored

[sacred geyser]

I'd just print the output bytes as they are

[sly sedge]

yush

i'll do that instead

[sacred geyser]

This is the kind of assumption that will lead you to waste tons of time some beautiful day!

Well, I say "day", but an issue can persist over weeks or months (or longer but we don't have to talk about that)

[sly sedge]

true

and u were right, it's actually set to 64

you just saved me a beautiful day (evening)

yeah alright well it's probably that other error

but i don't understand, the shader takes less than 2ms, it's definitely not slow enough for the frame to not be ready

and if i sync() the error message stays btw

ok well nvm it goes away when i sync

but it does not seem to solve the issue

and on top of all the other hints, you can tell the other shader doesn't launch because one node takes 2ms~ the other that's failing takes 0.8ms~

well it's not that it doesn't run, it runs but sets everything to 0

[sacred geyser]

If you tell the shader to process, and then try to read the results a few lines later, those 2 milliseconds have not passed

Calling for sync and waiting is pausing the code execution until the shader is ready, though

[sacred geyser]

Are the inputs to that shader valid?

[sly sedge]

i'm checking, i'll report back

ok so i think something goes wrong with the parameters, it does seem to launch, actually, when i rig the output of the shader to just write the inputs they show correctly in the output

i think it's just my calcs that went wrong 🤔 i'll dig more into it, you can consider my issue solved unless i'm come back in desperation.
Ugh tho when i had one light i messed with it a bunch to check if it was solid and i had no issues so whhhhhyyyyyyyyyyy is it showing now

Ok i found the issue, i kinda feel bad that you spent so much effort now

i pass a shadow geometry in the form of an array of triangles to the shader, and if it's empty, the shader just does nothing, i forgot this edge case

so that + the wrong offset in the shader that mix lightmaps together it really looked like there was a problem with calling the shaders or something in the likes. My bad sorry