Stretch in 3D, Dynamic Block

[Rseybert]

Hi all,

I work for an events production company.  I am trying to build a Dynamic Block for a video screen with its "Cone", or beam.

The idea behind the block is that you place the screen into the model where it needs to go and then stretch the origin of the cone to the projector lens.  

The challenge is that the projector is usually never on the same plane as the center of the screen so you need to be able to stretch along the X, Y, and Z axis'.  However, the block editor seems to not recognize the Z axis.

How do I accomplish this?!

I've attached the block for reference.  

Any help would be appriciated.

[Libbya]

You can accomplish it by changing the UCS with each block insertion so that you ARE stretching along the XY plane.

[Rseybert]

Libbya,

Can you please expand on this?

Thanks.

[Libbya]

As you found, the block editor does not recognize Z, so there is not any way to manipulate linework on all three planes dynamically.  You can insert linework on different Z coordinates, and stretch it, but the plane of the stretch action will be Z=0.  If the projector can be centered on the screen in any of the three planes, then the stretch action can occur on the other two by using the UCS command to change which axis is called the Z and assigning the Z axis as the direction that does not get changed.  Make sense?

[Rseybert]

Yes, that does make some sense.  Howeve,  Does this mean that I need to change the UCS everytime I need to edit the cone?

[Libbya]

Once the block is placed, you can manipulate the grips without changing the UCS and the grips will snap to snap points on the XY plane of the block but simple dragging of the grips without using coordinates or snap points is difficult at best.  See the attached file.  I added a dynamic 'muntins' block to the two window panes.  For placing the block I set the UCS so that the XY plane is the top of the glass.  The stretch actions still work after the UCS is reset to World.

[steven-g]

Doesn't the projector need to be centred on the screen to stop distortion ? Is it the idea that the cone angle remains constant and the screen size increases or does the cone just get longer.

[Libbya · Accepted solution]

I had a chance to play with your block and the attached file might demonstrate what I was talking about better.  I basically turned all the linework of the block sideways and then changed the UCS sideways similarly and inserted the block.  I then set the UCS back to World.  If you click  on the block there is a stretch grip at the apex of the cone.  With it set up like that, the apex can be stretched on the YZ plane but if the X always reverts to center.  

[Rseybert]

Thanks Libbya! Thats pretty much what I'm trying to achieve. After looking at your block I totally understand what you meant. Not sure why I didn't think of it before.

[Rseybert]

Steven-g, in an ideal case, yes, you want the projector to be center to the screen. However, thats not always possible.

[steven-g]

I asked because, I was thinking along the same lines as Libbya, that at least one axis would be in a fixed plane and that creating the block from another UCS would make it easier to use.