I'm very new. I'm trying to specify where on a polygon the center of transformations should be, when a polygon is an input to an l-system, as if the polygon were a leaf on a tree. If I use a transform operator to move pivot for translate and pivot for rotation, it does what I expect when rotating a grid. But, in the L-System, it's using the center of the grid rather than the pivot location, I think. I'm probably not understanding something basic. How can I have the l-system transform from somewhere other than the center?

well my guess is your leaf is either flat on the ground (top view) or upright (front view), either way just use matchsize and align max/min of Y or Z to whatever looks right.

Thanks! That does what I want. I don't understand why, though. I used Match Size with translate alignment position x .5 (the grid is 1x1). I guess the l-system is using the center of the bounding box?

It also works if I edit the "center" of the grid, and then use the grid as input to the l-system. I was looking for that and found pivot. I don't understand pivots or pre-transform, yet. I am having difficulty finding the concepts that examples demonstrate, while I try to learn houdini.