I would like understand how to place a point at a very specific location in 3-space. Mostly this is for rotation along axes not aligned with x, y, or z. In the Top, Front, and Right views I can only move the cursor on two axes, i.e. on a plane; the plane it moves on is (as far as I can tell) immutable. In the 3D view I can't really understand how the cursor moves around, but it always seems that when I place it where I want my selection point, the point ends up either far in front or far behind (in the direction perpendicular to the computer screen). I can tell from seeing the cursor moving in the other views when I move it in 3D view.

Is there any documentation on this that anyone can point me to? I am still fairly new to MoI and modelling in general so there may be something simple I am missing, and/or my terminology is wrong so I haven't been searching on the right words.

Thanks,
Rachel

Hi Rachel, welcome to MoI!

To place a point at a specific x,y,z location you just type those in directly when MoI is asking you for a point. So for example if you want to place a point at x = 40, y = 30, z = 5 you would type in:    40,30,5    and then push Enter and the point will be placed at that location.

Note that if you are in a location that uses the comma as the decimal point for individual numbers (like France for example where the fraction 1/2 in decimal is shown as 0,5 with a comma as the decimal point separator), you should put a space in between the coordinates rather than a comma.

If you are using 2D x,y coordinates where z = 0 you can just leave out the 3rd coordinate and only enter in the x,y . You can also enter in a single 0 as a shortcut for 0,0,0 and there are also some other coordinate entry methods like polar coordinate entry where you can enter in a distance and angle from the previous point rather than x,y,z coordinates. The different types of coordinate entry types are listed in the help file here:
http://moi3d.com/2.0/docs/moi_command_reference1.htm#__XYZ%20/%20Distance%20/%20Angle

When you start typing your coordinates the characters you type will go into the x,y,z coordinate input box which is on the bottom toolbar next to the Split/3D/Top/Front/Right view tabs:


So watch there as you type in your coordinates, you will see your text in that location when you start typing, then push Enter when you have finished typing the coordinates.


> In the 3D view I can't really understand how the cursor moves around, but it always seems that
> when I place it where I want my selection point, the point ends up either far in front or far behind
> (in the direction perpendicular to the computer screen)

It works by intersecting a screen ray with the construction plane - the screen ray is a line that goes from the 3D view's eye point out through the current mouse location - if you are looking at the construction plane at some kind of angle the intersection can possibly be a long ways off - it can be easier to draw points on the plane in the Top view instead of the 3D view, or at least angle the 3D view so that you are looking to some degree more downward at the plane rather than looking more towards the edge of the grid.


> the plane it moves on is (as far as I can tell) immutable.

You can actually relocate the construction plane somewhere else by using the View > CPlane command. But that's fairly advanced and I'd recommend just practicing drawing on the default construction plane for a while first, and maybe some more strategic use of the Top view rather than the 3D view would also make things easier as well. The Top view is fundamentally a 2D type view, with no perspective distortion on it or anything like that at all so it tends to be an easy place to draw 2D type stuff in.

Hope this helps, let me know if you are still stuck on anything in particular.

- Michael

Hi Rachel, also a lot of times you may want to snap points on to existing parts of objects like draw a line starting at the midpoint of some existing line. For doing that type of stuff you can use "Object Snap" - make sure it is enabled in the bottom toolbar, it will have an orange highlight on it when it is turned on. Then when you move your mouse nearby key points the current point you are picking will lock on to them, when you can use that it tends to be more convenient than typing in coordinates.

Also a lot of commands have their own individual numeric controls like when you're drawing a circle you can enter in the radius, or when you're drawing in a rectangle you can enter in the width and height - these commands often involve picking a point as well for the starting location like for the center of the circle. For picking the starting point when you type in coordinates, your keystrokes go to the x,y,z input box in the bottom toolbar. When you're on the next stage like with circle where you are then picking the radius in the second stage of the command you will see a new "radius" input field show up in the upper-right area of the main screen which is where all the options for a specific running command show up. When a command has an input field available like that then when you type characters your input goes into that field, so for instance if you want to draw a circle with its center at x = 24, y = 44, z = 2 with a radius of 3.5, you would start the circle command, and then type 24,4,2 and push enter (here your keystrokes have gone into the bottom x,y,z input field), and then at the next prompt where it asks you for the radius type in 3.5 and push Enter again - on that step your keystrokes will have gone into the radius field in the command options area.

So individual commands also have other numeric controls that you can use for their particular tasks as well.

- Michael

Hi Rachel, also if you haven't seen it yet, check out the introduction section of the help file:
http://moi3d.com/2.0/docs/moi_introduction.htm

It has some information about general operation of MoI and the section for Drawing / Picking points covers some of this stuff with some other information mentioned there too like how construction lines work.

Also in addition to that check out the video tutorials here which can also be a good help for getting started:
http://moi3d.com/2.0/docs/tutorials.htm

- Michael

Hi Michael, thanks so much for this information. I'm able to place points in arbitrary locations using the keyboard as you suggest (I'm already familiar with most of the other special inputs like radius, as they come up when that command is used). It's a little awkward as I have to write down the coordinates while moving the cursor into 2 or 3 views to get all the right numbers, but it works. I will re-read the intro because clearly I missed some stuff before!

Rachel

Hi Rachel, you wrote:

> It's a little awkward as I have to write down the coordinates while moving the cursor into
> 2 or 3 views to get all the right numbers, but it works.

Normally you would use direct x,y,z input when you already know the specific coordinate that you want to have, like if you're reading blueprints or plans that specifically call out a coordinate location. I had thought that's what you were asking about.

But it sounds like you're trying to do something different than that - something like eyeballing a location between multiple views or something along those lines? Something like that is probably better done by creating construction lines or drawing in helper lines and then using those to snap on to, rather than trying to write down existing coordinates. Mostly any time that you would be writing down coordinates it's a sign that some kind of snapping based drawing tool would do that job for you without any written down coordinates required.

Either construction lines, regular drawn lines, or placing a "point" object may be ways to get what you need done without writing own any coordinates. The "point" object is a marker that you can place and then snap on to later, it's available under Draw curve > More. Construction lines allow you to create temporary lines to help out with all kinds of alignment, extension, and positioning tasks, there is a bunch information on them here:
http://moi3d.com/2.0/docs/moi_command_reference11.htm#constructionlines

Can you maybe describe in a little bit more detail exactly what you're trying to do? If you have a particular file that you are working with it would also help if you could post the 3DM file as an attachment here.

- Michael