Sign in to follow this  
Kiel368

Unity Tiling textures using mod() in shader causes stripes on textures

Recommended Posts

Kiel368    239

Hi!

 

In my Unity project I want to apply various textures to my voxel terrain. I'm using a texture atlas. In some cases I needed to repeate the texture, so I found out mod() function to be the solution, but it produces nasty one-pixel wide stripes on my textures, which appears to be the first stripe of the neighbouring texture. I turned all the filtering off (apart from point, which cannot be turned off (which is logical) and I think this is the problem), but it did not solve the problem. And here's the question:

 

How to get rid of this stripe?

 

Possible solution (but i'd rather a simpler one):

 

Create an alghorytm that from an array of individual textures creates a single texture atlas, but it adds additional one-pixel padding to each texture (repeating the bordering pixels) - if sampler just takes that one pixel from the neighbouring texture due to point filtering (which cannot be turned off) it will fix the problem, but as I wrote - if you know a simpler solution, it is better for me.

 

Below I place the source of my shader:

I also attach some screenshots.

 

Input.color contains texture offset in atlas.

Thanks in advance for your help!

Shader "Custom/WorldShader" {
	    Properties {
	    	_MainTex ("Base (RGB)", 2D) = "white" {}
	    	_TileScale ("Texture size in atlas", float) = 1
	    }
	    
	    SubShader {
		    Lighting Off
		    pass {
			    CGPROGRAM
			    #pragma vertex vShader
			    #pragma fragment pShader
			    #include "UnityCG.cginc"
			      
				sampler2D _MainTex;
				float _TileScale;
			       			     
			    struct VertIn {
				    float4 vertex : POSITION;
				    float4 color : COLOR;
				    float2 texcoord : TEXCOORD0;
			    }; 
			     
			    struct VertOut {
				    float4 position : POSITION;
				    float4 color : COLOR;
				    float2 texcoord : TEXCOORD0;
			    };
			     
			    VertOut vShader(VertIn input) {
				    VertOut output;
				    output.position = mul(UNITY_MATRIX_MVP,input.vertex);
				    output.color = input.color;
				    output.texcoord = input.texcoord;
				    return output;
			    }
			     
			    float4 pShader(VertOut input) : COLOR0 {
				    float2 newUVs = float2(fmod(input.texcoord.x, _TileScale) + input.color.r, fmod(input.texcoord.y, _TileScale) + input.color.g);
				    return tex2D(_MainTex, newUVs) * (UNITY_LIGHTMODEL_AMBIENT * 1.5);
			    }
			    ENDCG
		    }
	    }
    }

Share this post


Link to post
Share on other sites
C0lumbo    4411

My immediate thought was also that it was a bilinear filtering issue, but you say that point sampling doesn't fix it. Adding a little padding around atlas textures is something that's pretty commonly done and sounds like a decent solution.

 

The only other thing that occurred to me is that maybe it's a floating point precision thing. Your UV coordinates are being passed to the GPU as floating point numbers, which are incredibly accurate, but the further away from zero they are, the less precision they'll have after the decimal point. A floating point number has no problem accurately specifying a single texel in a 1024x1024 texture if the UV is near zero, but you'll find that if your UVs are up beyond 1000 or so, then the amount of precision after the decimal point becomes too small and you could expect precision artifacts.

Share this post


Link to post
Share on other sites

If I understand the issue correctly, that's an old, well-known problem. You will need to calculate (and specify in your texture lookup) the mip level or the gradient (whichever is supported by your hardware). Mip-mapping is still turned on, right? (also check driver settings to avoid surprise, driver may force it on even if you don't)

 

The problem with functions like modulo is that the hardware calculates the mip level from the gradient, and the modulo function being discontinuous causes big "jumps" in the gradient. Which, of course, causes the hardware to pick the wrong mip level at the discontinuous locations.

 

What surprises me a bit is that you think you're getting vaues from a neighbouring texture atlas piece. That isn't normally the case and it doesn't really look like that to me in the screenshot either (but who knows for sure -- you could extend each tile with its border pixel value as padding to "work around" if nothing else helps, or make a "control color" border around each tile to be sure, that is a color you would not normally expect to see).

Edited by samoth

Share this post


Link to post
Share on other sites
tanzanite7    1410

You might have bad mipmap selection as mentioned, however that would generate only 2x2 spots of garbage - that clearly does not match the picture.

 

Would guess it is the half texel issue (depending on whether Direct3D or OpenGL is used - (0,0) is either corner [OGL] or middle [D3D? - or have they changed that?] of texel) - however, the error seems to cover more texels that one would expect on such a case (might be just my eyes - the error should be about 1, rarely 2 texels worth).

 

My guess is that your texture coordinates are just wrong. Take pencil and paper and check that the final coordinates are exactly what they should be.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Similar Content

    • By Affgoo
      About us:
      We are a team of 14 developers developing multiple mid scope games both are over halfway complete. We polish all of our games and focus on quality.


      We are a small team, everyone currently on the team and future teammates must be interested in game development as a whole and not just one role, being a small indie company it is very important that you can wear a few hats and not just one. Everyone on our team is a game dev.

      looking for:
      3d Artist (hand painting a huge plus)
      3d Animator
      entry level Software engineer with reasonable skills in c# / shaders. 

      ^ requirement for all positions: A true love of game development and to be very self motivated.
      We are a very active team, you must be too. 


      If interested or for more information add me on skype: nicholas.boucher4


      Atlas Sentry art style: (art complete)(code complete)
      http://www.slidedb.com/games/atlas-sentry

      Rat n Gat art style: In Devlopment

    • By EvaBalikova
      Main menu in Feudal Alloy. 
      twitter
    • By Jcyshadow97
      Hi guys,i m looking for someone that can work with me on a "top-down" multiplayer fps as 2d and 3d artist.I used photon server and i can take the part of programming.For now i made only the basic gameplay of the game that include shooting,switch weapon and and damage player.If someone can help me please contact me via e mail: 270514974@libero.it.
      I really appreciate your collaboration and hope you have a good day.....
      Thanks for you time to read the post
      At the bottom i attach some screenshot of the current game,i m sorry that i can't attach a video...



    • By Raptor42
      I'm looking to form a new game development team, mostly for training purposes.
      About me:
      I'm a student - Unity C# developer, who worked part-time in this industry for a couple of years already. I've been a lead developer in many "random collab groups" as well as a few companies. I specialize in creating 2D games for Android, but I'm looking forward to trying out new things - especially 3D development.
      Currently, I've got one Android game close to a release so I'd work for this team in my spare time. 
      About the project:
      I've been thinking about creating a simple tycoon-like simulation game for Android (and PC eventually), inspired by the Game Dev Story (initially released by Kairosoft in 1997) https://en.wikipedia.org/wiki/Game_Dev_Story 
      I haven't done much planning though, therefore I'm looking forward to hearing out your ideas.
      Right now, I've only created a test 3D scene using placeholder models and implemented a simple pathfinding system for me to play around with:
      https://i.imgur.com/xAd0l4o.png
      https://i.imgur.com/nHZerOT.png
      I'm looking to work with people who are:
      - willing to take a position of a: 3D modeller/2D artist/Designer
      - not necessarily very experienced, but eager to learn and improve their skills
      - active - check in at least once a day
      If you'd like to apply for a different position which I didn't list here, you are welcome to contact me as well.
      While this project is created mostly for learning purposes, if we ever get to release it and generate any revenue - you will recieve a certain percentage of it.
       
      To Apply:
      Send an email to rk.softwaredev@gmail.com
      Introduce yourself and attach an example of your work (if you have any)
    • By EvaBalikova
      Hello.

      We're a two-member team and I'd like to introduce you our game - Feudal Alloy. 
      It's a metroidvania-style action RPG with fishbowl-powered medieval robots.

      We've been working on the project for a few months. I'd be happy for any feedback.
      teaser
      homepage
      twitter
      facebook
       
      Our Steam page is public now: 
      steam link
       
       



  • Popular Now