I think in your earlier experiments you said that when you draw an irregular sprite to the screen with filtering enabled for that image, it blends with the background fine, but that the pixels at the extreme edges of the sprite do not, is that right? If you were to switch on polygon smoothing, those pixels at the edge of the image would blend just as well as those within the sprite.
The amount of color contribution from the sprite image is blended with the color in the background pixel so that the resulting background pixel is some result of the two combining, as a float value. It should then be perfectly possible to draw another sprite at the same coord, next to it, and it should also contribute to that pixel value, which means it also takes into account the other sprite's pixel. You shouldn't need anything else to make them appear to be perfectly lined up and antialiazed with each other.
It shouldn't even require a mesh. In fact, the idea of a mesh is just an idea of a number of joined together triangles, usually in a strip, where two of the previous vertexes for the previous triangle are shared by the next triangle. But that gives you rows of triangles, not a 2d grid. With polygon smoothing on you should get seamless rendering.
The question might be whether it's really viable to use polygon smoothing all the time since it overrides any other blend modes you might want to use. And then you might want to look at full screen antialiasing.
The amount of color contribution from the sprite image is blended with the color in the background pixel so that the resulting background pixel is some result of the two combining, as a float value. It should then be perfectly possible to draw another sprite at the same coord, next to it, and it should also contribute to that pixel value, which means it also takes into account the other sprite's pixel. You shouldn't need anything else to make them appear to be perfectly lined up and antialiazed with each other.
It shouldn't even require a mesh. In fact, the idea of a mesh is just an idea of a number of joined together triangles, usually in a strip, where two of the previous vertexes for the previous triangle are shared by the next triangle. But that gives you rows of triangles, not a 2d grid. With polygon smoothing on you should get seamless rendering.
The question might be whether it's really viable to use polygon smoothing all the time since it overrides any other blend modes you might want to use. And then you might want to look at full screen antialiasing.