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apocriva
PostPosted: Wed Mar 16, 2011 12:46 am 
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Posts: 8
Image

At certain non-whole-pixel translations, I'm seeing terrible seams in TiledMap. I believe the root cause is due to Image.getSubImage's texture coordinates being on texel borders, rather than in the centers of texels. This would also manifest itself in anything else using SpriteSheet, or subImages, but I see it quite glaringly in TiledMap.

The reason the seams are white for me is due to the texture wrapping, and the opposite edge of the texture being white.

Ultimately, all that should be solvable by putting a few half-texel offsets into the rendering code in Image.java... Maybe in drawEmbedded() ~line 523 or so...

Code:
  float texelHalfWidth = (1 / textureWidth) / 2;
  float texelHalfHeight = (1 / textureHeight) / 2;

  GL.glTexCoord2f(textureOffsetX + texelHalfWidth, textureOffsetY + texelHalfHeight);
  GL.glVertex3f(x, y, 0);
  GL.glTexCoord2f(textureOffsetX + texelHalfWidth, textureOffsetY + textureHeight - texelHalfHeight);
  GL.glVertex3f(x, y + height, 0);
  GL.glTexCoord2f(textureOffsetX + textureWidth - texelHalfWidth, textureOffsetY
    + textureHeight - texelHalfHeight);
  GL.glVertex3f(x + width, y + height, 0);
  GL.glTexCoord2f(textureOffsetX + textureWidth - texelHalfWidth, textureOffsetY + texelHalfHeight);
  GL.glVertex3f(x + width, y, 0);


I would try the change myself, but I'm extremely new to Java and especially Slick, so I'm completely clueless as to how to build Slick myself. :)

Thoughts? This would certainly fix my problem, though I can't be sure it wouldn't cause knock-ons for others. Integers and floating points never play well together. :roll:


Last edited by apocriva on Thu Mar 17, 2011 2:04 am, edited 1 time in total.

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kevglass
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PostPosted: Wed Mar 16, 2011 10:17 am 
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You need to change your filtering on the tileset image to use NEAREST.

Kev
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apocriva
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PostPosted: Wed Mar 16, 2011 1:35 pm 
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I can't check at the moment, but I thought that the TiledMap loader, when loading tilesets automatically, was already setting the filter to NEAREST. The tiles certainly appear to be using NEAREST to me, even if it's not evident from the little screengrab.

In any event, I'll give that a shot tonight.
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R.D.
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PostPosted: Wed Mar 16, 2011 1:57 pm 
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in my project the TiledMaps are correct...

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apocriva
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PostPosted: Wed Mar 16, 2011 6:33 pm 
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I don't see the issue as long as all the pixel offsets are nice round numbers. If my matrix stack has a scale and translation in it that are non-integral, I see the seams. I don't see them all the time -- but as I slide through a floating point translation for map scrolling, the seams flicker on and off.
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apocriva
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PostPosted: Thu Mar 17, 2011 1:45 am 
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Well, I'm pretty sure that I just won't be able to use translation/scaling the way I wanted to.

This is really bad!

It appears to just be a texture rounding error, and I am totally at a loss for what to do about it. I can't really be rendering things pixel-perfect and still be able to scale nicely... I'm just using g.scale() right now to zoom in.
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apocriva
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PostPosted: Thu Mar 17, 2011 2:04 am 
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I'm getting around this issue by putting spacing between the sprites in my spritesheets. It feels gross, but it works.
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R.D.
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PostPosted: Wed Mar 23, 2011 11:35 am 
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I declare this as a bug now too.
For something like "fading out" to a point of the map this gives you the seams.

I will try it with putting space between the tiles...

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kevglass
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PostPosted: Wed Mar 23, 2011 11:44 am 
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Can you knock together a little example of the issue you're seeing. All the demos/tests work without seams.

Kev
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R.D.
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PostPosted: Wed Mar 23, 2011 12:26 pm 
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Jepp, here we go:
http://npshare.de/files/e09fc0ae/Seam.zip

Use up and down to change the y translate. At 0.0499999 or soyou can se the seams.

It might help to use a round value for the translate...

EDIT:
It's ALWAYS at x.49999997.

EDIT:
okay it seems that it also happens with x.50000000000000 values.
Workarround:
Code:
g.translate(-round(pos.x), -round(pos.y));

...

public int round(float value) {
      if(value < 0)
         return (int)(value - 0.5f);
      else
         return (int)(value + 0.5f);
      
}


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apocriva
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PostPosted: Fri Mar 25, 2011 11:44 pm 
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My major issue has been since I scale up everything using a g.scale (doing things in a 16-bit style, so I likes me some chunky pixels!), even if I have whole-number g.translate values, I'm still getting rounding errors on certain resolutions. That's really the root of my problems -- everything'll look fine on my monitor, but when I try on another that has a different native resolution, I get seams.

Ultimately, putting a buffer around my tiles has solved the issue without a great deal of headache for me, so I've been concerning myself with other things. It could very well just be a rounding issue at the hardware level, and I refuse to stress myself out over hardware. :) hehe
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