Another to?

 From:  Michael Gibson
689.10 In reply to 689.9 
Hi Brian,

> 1. I presume with MoI that x is l to r, y is vertical, and x is depth.

MoI uses a coordinate system where x and y are flat on a tabletop, like a blueprint for a building. If you are looking straight down at the blueprint x is running from left to right, and y is running vertically.

Then the z direction protrudes upwards from the tabletop surface. If you can imagine the lines of your blueprint pushing up into walls, the walls would be extending along the z axis direction.

When you switch between different views, you end up looking at different world axis directions. Like for instance from the top view the x axis travels left and right along the screen and the y axis travels up and down on the computer monitor screen. If you switch to a "front" view, then it is the z axis that is running up and down on the monitor.

> 2. I am completely lost with the sentence, "Pick the first point of the
> "revolve"? axis? snapped to the "oriigin"?, and the second point on the Y axis."

The "Revolve axis" is a line that you draw inside the revolve command - it defines the "hinge" that will be used to swing your profile curve around to create the revolve.

This might be clearer:

First, select the circle, then run Construct / Revolve. There will be a prompt in the upper-right corner of the window that says "Pick revolve axis start point". This means that MoI is waiting for you to pick one point to define the base point of the revolve axis, pick it in the spot indicated above - this is the world origin and there should be an "origin" snap when you move close to it unless you have turned off Object Snaps in the bottom bar.

After you click that point, the prompt will change to say "Pick revolve axis end point" - so now pick the second point shown above. This is along the world y axis, which is the vertical direction when looking from the Top view.

After you pick those 2 points in that direction, it will generate this type of a revolved surface:

You can kind of see that the circle was rotated around that line, with the line acting as kind of like the pin in a door hinge.

Hope this helps!

- Michael