Tracer Effect

[main yacht]

Hi

These are some tracers
I want to replicate this effect with a shader (I can't use gameobjects)
How do I go about it?

Specifically, I need help with the shader itself

I am currently rendering using Graphics.DrawMesh

[royal vigil]

Ok, based on this info alone, it doesn't change my reply, if you have a trace mesh already(for example, if you generate it at runtime), you just need to apply a shader to it. Any kind of shader would work really, but you probably want an unlit shader, so that the trace is not affected by lighting. I'd try the unity unlit one for starters, as I suggested.

[main yacht]

The shader is the point!!!!!!!!!!!!!!!!!!1

@royal vigil
Trail renderers are no good, the variable length depending on the speed is a bad thing
A small mesh with bloom is problematic because eventually there won't even be one pixel to display for post processing

I need to create an effect as seen in the video, where bullets gradually fade out of view instead of instantly due to aliasing
https://www.youtube.com/watch?v=jdCfhhJpi9E

[royal vigil]

Do you understand how shaders work? Vertex shader runs for each vertex of a mesh, transforms the vertices position to clip space + some other transformation and passes them on. The GPU fills the screen space triangles with pixels and calls a pixel shader for each screen pixel in the visible triangle. That's super simplified, but the point is, you need something for the vertex shader to work with. It can't make things out of thin air. That's why you need a mesh of the trace. That or it has to be a full screen shader, a post processing effect basically.

[royal vigil]

In thia video there's probably more than just a shader involved. It's likely that they're employing some advanced anti aliasing techniques, like ssaa or something.

[main yacht]

It is something already though

Current look

The problem

[royal vigil]

Well, how you rendering it? It's weird that a long shape mesh would render as a point like that. Unless it's rotated orthogonally to the camera.

[sly rock]

Is the problem that it appears too small when far away?

For that exact problem I used a shader that extrudes the mesh (adds the normals to vertex positions) over distance to camera

[old bone]

What stops you from using Particle System? Every game source and engine I had a chance to touch used Particle System implementation, this is like battle proven solution. It does many things out of the box.
Since you are restricted to Graphics.DrawMesh, I would look into possibility to limit minimum size of the object either though mesh or shader itself, I would dig into particle system code and see how its done in Render tab.
I have not done this that way, sorry to be useless.
But.
With Particle System you can build physical bullets, or ray cast based. You can have a bullet mesh, or/with traces that keeps its minimal size on distance, as alternative you might have different particle blending half way through to display far tracer as more visible/simplified one. With visibility over distance you might replace it with simple glare texture.

[hexed orbit]

I suggested particles or VFX Graph specifically for this purpose in the other thread that we already had

Particle System and VFX Graph particles already let you define min/max screen size, and then you'd just fade the color or alpha when it get far away

[main yacht]

This is what I'm looking for

[main yacht]

As an object

I'm demonstrating that the effect is much worse when you are facing towards the bullet

I don't want to use a particle system, it would be annoying to write the code for setting the positions and direction for every particle in the system, that is what I did the first time around

This is a thread about creating a shader for a small mesh to keep it visible as it gets further away

[sly rock]

You use shader graph?
Add the vertex normals to the vertex position in the shader. This makes the mesh extrude outwards along its normals.
Get the distance to the camera and use that as a multiplier for the extrusion.

[main yacht]

Not familiar with it, the creation of the shader is precisely what I need help with

Which one?

[sly rock]

I dont use URP but probably URP > Unlit Shader Graph

[main yacht]

Unlit?

[sly rock]

Since it will just emit light it doesnt need to be lit

[main yacht]

Right

[sly rock]

Lit = receive lighting, shadows and such

[main yacht]

@sly rock Well that's not right...

[sly rock]

Thats the idea, just need a very small multiplier based on distance

Is the position input World space or Object space?

If you unplug it you will see

[main yacht]

WORLD

[sly rock]

Good

[main yacht]

@sly rock ???

It's not even visible in the scene

[sly rock]

You missed the 'very small multiplier' part

Also your muliply should be before the addition, not after

You only need to multiply the normal with distance * some small number

Then add it to the position

[main yacht]

Looks like it just tears the mesh apart

[brittle forum]

If you push out the normals you need to have a continuous mesh. No split edges. All shared vertex indices.

Otherwise u get that effect

Another thing to consider that I tend to forget how to do (but remember to do) is you need to account for the fov of the camera for scaling problems like this. When multiplying by the projection matrix iirc the value you need for accounting for it is often stored in the w of a transformed xyz(w).

[main yacht]

@brittle forum @sly rock This kind of works

But the object likes to disappear before it's fully off screen and the scaling is really weird

[brittle forum]

You'll need to update the bounds of the object to reflect the increased scale.

It's getting culled

[main yacht]

uhuh

[brittle forum]

Pretty sure.

[main yacht]

how

[brittle forum]

This is a tricky one. The way you have it written it could almost be a c# script.

But the bounds are a cpu side thing

So you can't get them in a shader

It's J a problem with making things larger than they really are in shader

[hexed orbit]

A solved problem with particles

[brittle forum]

You can still use meshes with particles too.

[main yacht]

I'm not going to use a particle system

[hexed orbit]

I recommend VFX Graph, not the PS

[main yacht]

What is the VFX graph?

[hexed orbit]

GPU particle simulation

[main yacht]

See what I mean by weird scaling? It's not entirely uniform and is prone to weird angles

[hexed orbit]

A more flexible system than PS since it can do anything with any kind of data you feed into it, not just with predefined modules

So fading particle color over distance can be done within it without shaders
Screen space scaling is an included operation

[main yacht]

I'll look into it

Hell, I might be better off with a 2D texture rather than a mesh. I mean, look at this

[hexed orbit]

It's not quite possible to tell which one that is

[brittle forum]

U still have the problem you're describing where it's not visible from the front

[hexed orbit]

A 2D Texture will have to be made into a mesh to be rendered

[brittle forum]

That's tru too

[main yacht]

A mesh with 2 tris

Rather than my 4

We'll see

[hexed orbit]

Billboarding a stretched quad towards camera is tough to do manually, and tougher if it also needs to retain solid appearance frontally as hol mentions
Luckily VFX Graph has all kinds of billboarding options for quad particles

[sly rock]

I used a more capsule-like mesh so it extrudes more uniformly

[sly rock]

Not sure how this would work when viewed from behind/front

[royal vigil]

I wonder if frustum/distance culling is playing a part in what they describe as the "object disappearing"..?🤔

[royal vigil]

That's how you'd see it in real life though. If the trace is facing you, you'd only see a dot.🤷‍♂️

[royal vigil]

That is if they were visible in real life.

[main yacht]

What?

[main yacht]

Well, yeah. But it would still have bloom. The issue is not it being small, but bouncing in and out of being invisible due to aliasing

[royal vigil]

You'd be surprised, but normal bullets don't produce shiny traces as they fly through the air.

In real life*

[main yacht]

I'm not twelve, I know this

[royal vigil]

Can you record a video demonstrating the issue?

I feel like it's less "aliasing" and more has to do with the shape of your mesh.

Is it just 1 long triangle?

[main yacht]

cone

[royal vigil]

Hmm.. Okay. So can you record a video of what it looks like?

[main yacht]

It's too abrupt

I dunno what you're looking for, small object get so small that it become < 1 pixel big

[royal vigil]

Yes, I just wanted to confirm I understand the issue correctly.

[main yacht]

The fact that post processing is... post processing doesn't help the issue at all, so it's either blooming really bright or completely invisible

[royal vigil]

Well, what Osmal was suggesting should work. Although, I'd think what Spazi was suggesting is a more correct approach and provides more room for customization.

[main yacht]

I will look into converting over to a VFX graph, good excuse to learn it anyway

[sly rock]

If that doesnt work out, try the extrusion approach, you were very close to having it working. The mesh just needs to have a couple more vertices and no hard edges

Funny to hear the approach called incorrect when it solved this exact issue for me

Ofc the downside is having a few more vertices compared to a quad, but it probably wont make a difference

I dont remember running into any culling issues 🤔

[hexed orbit]

In my experience you run into those always when scaling up a mesh in vertex stage
It'd be simpler to only scale down

[sly rock]

Yeah it makes sense, I need to check again if its an issue

[main yacht]

I can just... scale it outwards. Like from the cone's tip.