Pixel perfection, texel snapping

[micktu]

        if(Futile.isOpenGL)
        {
            Futile.screenPixelOffset = 0;
        }
        else //directX needs to be offset by half a pixel
        {
            Futile.screenPixelOffset = 0.5f * Futile.displayScaleInverse;
        }

While this is correct, it is not a solution. Subpixel movement will still get artifacts most of the time, on both OpenGL and DirectX. This could be resolved two ways: the less elegant is to snap every object's position to points (e.g., round() for OGL, round() + 0.5 for DX; the more elegant one is to snap inside the shader, and in fact, a shader like this is already a part of the official Unity kit. Grab Unity 4.2 shader source and take a look at Sprites/Pixel Snap/Alpha Blended.

[MattRix]

Yeah I'm not a big fan of snapping the objects themselves (that will create other issues), but doing it in a shader is an interesting approach. I don't think I'd make it the default, but having pixel-snapping shaders as an option in Futile would be handy.

[micktu]

On the other hand, I thought that eliminating subpixel positioning by snapping vertices to points may not be a bad idea after all. It will also allow people to use their own shaders without integrating them with pixel snap algorithm. I will try that as well, it's an easy patch after all.

[MattRix]

Yup, you could go into the FRenderLayers and manually round the position of each vertex. I think that'd work but it'd introduce a sizeable processing overhead if you were doing it every frame.

[micktu]

I don't think a call to a single native method will cause any significant overhead, I even think that it will be a tiny nice optimization (don't update vertices if they round up to the old values). I haven't digged into the renderer code yet, but I'm pretty sure it's not reuploading vertices unless they are changed, so it'd be just a bonus condition.