All parametric/All the time. There's much to say, please stay tuned.
Here's some stuff I made over the last few months.
If a child does not doodle with crayons, he/she will not build skills.
Doodling represents the world in a diagrammatic way, not by what it looks like, but by what it means. A kid can make a meaningless photograph, but not a meaningless doodle.
If a tool is cheap and readily accessible, people will doodle with it. Paper, pencils, crayons, mud, clay, Sketchup, Blender and even Rhino are cheap and accessible. Few people will doodle with $5000 finger paints. Besides, they're kept in that drawer with all the important documents and work stuff, best not to even go in there, looks boring.
If tools are expensive, they will be used for serious purposes, by serious and expensive people, who walk around with serious expression on their faces so you know that they are expensive. They will not laugh at your poop joke. They will look like this (minus the fabulous turban):
Serious people do not doodle. They do NOT play with crayons.
They also can't draw for poop.
I've heard this question for issues ranging from folks wanting to do accurate and complex curbing for parking lots to wiggly columns. I'll show an example for how to make structural supports for curtain walls. The same principle applies to do any category: make a dummy 3d shape in massing and use the edge of it to guide a sweep made in any other in-place mass category. Hackalicious
Sorry again for poor sound quality, one of these days I'll get a real mic.