We now floor the corner position and use this position as origin.
This gives us perfect derivatives in all cases even if very far from the origin.
Unfortunately this won't fix the low precision of coordinates used for computing the actual grid size, resulting in thick, non-smoothed lines.
Also did a bit of refactor how the axes are drawn.
Do not use the inverse perspective matrix inside the shader to recover world positions.
That leads to severe float imprecision leading to nasty artifacts.
Instead we compute the world view vector for each pixels and do a ray to plane intersection.
We are still getting low precision derivatives when going far away from the origin, and thus artifacts.
This commit also fixes the non-appearing negative Z axis in 3D view.
Removed infinite details and went for decreasing details with the distance instead (like the axis aligned ortho view auto sized grid).
Separate drawing of the Z axis into 2 pass (using shading group) to render ordered transparency with the main grid pass.
