I have a mirror in my scene that I want to have reflecting a certain spot on the other side of the room so that I can get it in the scene. I just don't know how to aim it to show in the render. How do I aim a mirror to reflect what I want?

use the TOP view and show your camera. Then set the mirror to point so the angle between it and the camera , and it and the target are equal.

Then switch to camera view and do an area render of the mirror to check.

If you have PP2014, use the raytrace preview window

use poser progressive render.  it's like luxrender or maxwell render, but fastsr and more poser-centric.  avoid caustics for now.

Coincidentally I noticed this utility at D3D's web site a couple of days ago. I haven't tried it yet so I don't know if / how it works, but it sounds like it could help.

Basic geometry skills?

The mirror, the object, and the camera form a triangle.  You know their locations (x/z coordinates) to be able to determine the lengths of each side.  Link to equation.

From that you can get an angle.  Then you can use said angle (solve for mirror's location) to figure out which angle the mirror needs to be pointed in order to see the reflection from the camera.

Quote - Basic geometry skills?

The mirror, the object, and the camera form a triangle.  You know their locations (x/z coordinates) to be able to determine the lengths of each side.  Link to equation.

From that you can get an angle.  Then you can use said angle (solve for mirror's location) to figure out which angle the mirror needs to be pointed in order to see the reflection from the camera.

Thanks, this is the information I think will work best. The problem is I am not too good with geometry...out of practice for years. I looked at the site you gave and it didn't make sense to me. Let me ask how to get the side lengths of the triangle.

If point a (mirror) is at lets say 4x and 3z and point b (object) was at 9x and 2z with point c (camera) at 9x and 6z I would be able to determin the distance between each object by ??? How do I get the side lengths?

Like this?

http://www.regentsprep.org/Regents/math/geometry/GCG3/Ldistance.htm

Here's an example scene. I have a room set up, and a chair that is to be in the mirror. This pic shows the view from my camera. You can't see the chair.

The green square is D3D's reflector, with a green line showing the camera view path, and another line from the mirror showing the reflection path. (The reflector is not green normally, I did it to show it easier)

You guys do know that you don't really have to aim a mirror, right? It'll reflect anything you put in front of it. What you have to do is position the CAMERA so you can see what is being reflected in the mirror.

Student: Wait, wait professor! I once saw this movie where this man was in prison and the only way he could see what was outside his cage was to hold a mirror out the window and aim it.

Good point, Johnny. Yes, you can move any point around, but once again the mirror will show anything that is in front of it. It is only when the veiwer or camera is in the right position in relation to the mirror  that it will see what you want it to see.

Quote - You guys do know that you don't really have to aim a mirror, right? It'll reflect anything you put in front of it. What you have to do is position the CAMERA so you can see what is being reflected in the mirror.

I think the original question is slightly misworded, and the original poster was really asking for help in achieving, once having set the camera, how to position an object out of view to be seen in the mirror. Which is what the replies have been about, whether it's using trigonometry or in my case D3D's freebie.