Transparent Textures Flicker

the-environment-guy

Hello, I'm experiencing 3D render issues in Godot 2.1.1 Stable. Transparent textures flicker as the screen moves, posted a video of it on Youtube. Texture is double sided, perhaps there is alpha sorting or depth limit problem?

Megalomaniak

Looks like it could be something to do with self-shadowing. Might be able to offer more if I could take a look at the scene. would you be able to share it for exploration?

edit: one more thought, make sure you have turned of default viewport lighting, that is view dependent and doesn't get included in exported games anyhow.

the-environment-guy

Hi, cetainly its on Github. I would apprciate it. Its in project/scene/mountain Please don't mind the texture seams, unoptomised models and scripts. I roll over code from project to project and have since fixed the issues it has. This Was a two week slap together project to prep for doing higher end 3D graphics. Needed to get a feel for the engine

https://github.com/TheEnvironmentGuy/Godot-MountainTop-Environment/tree/master/project

Megalomaniak

Since it looks like it might just be to do with back-face culling I thought I'd try enabling double sided rendering(remember that textures might be double sided, but material settings also feature a boolean control for polygon rasterization) however while it improved the overall look of the foliage it didn't get rid of the flicker. It seems to specifically have something to do with the face normals and the draw order.

in other words yeah, I think it is z/depth-~~fighting~~sorting so things that could help is using imposters for distant elements and higher tessellation for nearby foliage. Also playing around with camera depth during runtime might help avoid it.

edit: see depth sorting here: https://www.sjbaker.org/steve/omniv/alpha_sorting.html

MagicMike

Hey. I know it's been a year but are you still having this issue?

I'm using Godot v 3.1.1 stable and I get the exact same issue if I pass in any value to the alpha channel in my visual shader, even the value of 1 (solid no alpha).

What it seems like is that Godot sorts alpha transparency objects by the distance from their origin to the camera. This is a speed trade off I believe, because the other option is to draw them multiple times.

This is fine for some particle effects, but doesn't work for grass, hair, etc.

Anyways... I think I'm just going to build my project without alpha transparency for now. Different design decisions.

Also, for certain things this kind of Z sorting is ok. I was able to do eye-lashes for my character for example, but couldn't do hair well with the Z sorting. Smaller objects that do not intersect each-other work fine. So for example you could do many more smaller grass chunks that don't intersect each other or other physical objects. As far s looking good from different angles you could still have them face different directions but not intersect (so there's no Z sorting problems).

So for example, this cross shape you have below: --|--
It could be three separate objects and would likely Z sort correctly if my guess on how it's Z sorting is correct.

For me... I'm trying to figure out how to render longer hair well.

Calinou

@MagicMike Try setting Depth Draw Mode to Opaque Pre-Pass in the Parameters section of the SpatialMaterial. This will make Godot render opaque parts of the material in a separate pass to minimize transparency sorting issues.

I don't know how to change the depth draw mode of a ShaderMaterial though.