[Bomber] Ability to specify particle pivot

IMHO, the Bomber needs the ability to specifiy Particle Pivot X/Y.

Why? Because sometimes you need very precise control over the way your particles spawn fr om a Chance map, and over how they transform when squashed or rotated.



<example> (see image below):

A forest of trees. I need the trees to grow fr om the Chance area (the red ellipse). Obviously, the particle pivot needs to be at the base of the tree - the ground - because that's usually the location a tree grows from. It also happens to be the point around which a tree should rotate and squash.

So, I like the density in the upper forest, but I don't like how particles spawn/squash/rotate etc. If I compensate for the hard-coded pivot by modifying the particle itself, it is reduced to a quarter of its original size. As a consequence, the visual density is reduced drastically. This effect can be seen with the lower forest.

Note that the Bomber in my example has its Density set to its maximum, and -- for artistic reasons -- I really do not want to introduce half-transparent particles by increasing Details and Roughness.

Obviously, the ideal solution would be to use the upper particle and just change the particle pivot to x=0.5/y=1.0!

Instead, if I don't want to loose particle density, I'd have to use an offset to shift the whole forest up to wh ere it really should have grown. And then the particles would still squash and rotate the wrong way, and not sit tightly on the edge of the Chance map.

</example>

Can't be to hard to implement this, now can it?

And here's how that super-tall mountain would look when bombed. Yup, can't offset our way around that one. The "visually incorrect" depth sorting is here to stay.



Conclusion: Please don't force us to compensate for the hard-coded pivot at the particle level. Give us an option to tweak this in the Bomber itself.

Quote
Until we can have a bomber/particles that take advantage of the unbounded 'Free' patterns, this would be nice.

A Particle map input always samples the coordinate area 0..1 in x and y. Sampling from a larger coordinate area (say 0..5) will not solve the problem presented above. Furthermore, I'm not sure it makes sense for a particle to be unbounded -- it has to be bounded by definition.

What's important here is the origin of transforms for operations like Squash, Squash Chaos, Rotation and Rotation Chaos -- i.e. the particle pivot. The problem is: it always sits at x=0.5/y=0.5.

In my super-tall mountains example, the mountains on the right side exhibit visually incorrect depth sorting because they are squashed from the x=0.5/y=0.5 origin when they really should be squashed from x=0.5/y=1.0.

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