3D Rotating Hotspot

[JGoode]

Hi,
I am playing with the 3D Rotating hotspots. Is there any way to change the plane which the hotspot rotates around? It is currently horizontal/flat but I want it vertical instead. I have used the example given by graphisoft and used the parameters in the code but I don't know how to manipulate it to do what I'd like it to.

Any help would be much appreciated.


Here is the Graphisoft example code for it.

 unID = 1
! --------------------------------------------------------------------------------
! Center
! --------------------------------------------------------------------------------
hotspot 0, 0, 0, unID, ang, 6     : unID = unID + 1

! --------------------------------------------------------------------------------
! Base
! --------------------------------------------------------------------------------
hotspot 0.2, 0, 0, unID, ang, 4     : unID = unID + 1

! --------------------------------------------------------------------------------
! Moving
! --------------------------------------------------------------------------------
hotspot 0.2 * COS(ang), r * SIN(ang), 0, unID, ang, 5     : unID = unID + 1

! --------------------------------------------------------------------------------
! Reference
! --------------------------------------------------------------------------------
hotspot 0, 0, 0, unID, ang, 7     : unID = unID + 1

[Bruce]

First thing: The reference hotspot cannot be the same as the centre hotspot. An imaginary vector drawn from the centre hotspot to the reference hotspot forms your rotation axis...like the axel/hub of a wheel.

To rotate in the vertical plane, the z-axis coord of the moving hotspot needs to be used, and either the x or y coord left at 0.

E.g. to rotate around the x axis, using your parameters, would be:

ROTX ang
HOTSPOT 0, r, 0, unID, ang, 4 : unID=unID+1 ! Base
HOTSPOT 0, r*COS(ang), r*SIN(ang), unID, ang, 5 : unID=unID+1 ! Moving
HOTSPOT 0, 0, 0, unID, ang, 6 : unID=unID+1 ! Centre
HOTSPOT 1, 0, 0, unID, ang, 7 : unID=unID+1 ! Reference
DEL 1

I can’t test this right now, but it should be something like this.

[JGoode]

Bruce wrote:
First thing: The reference hotspot cannot be the same as the centre hotspot. An imaginary vector drawn from the centre hotspot to the reference hotspot forms your rotation axis...like the axel/hub of a wheel.

To rotate in the vertical plane, the z-axis coord of the moving hotspot needs to be used, and either the x or y coord left at 0.

E.g. to rotate around the x axis, using your parameters, would be:

ROTX ang
HOTSPOT 0, r, 0, unID, ang, 4 : unID=unID+1 ! Base
HOTSPOT 0, r*COS(ang), r*SIN(ang), unID, ang, 5 : unID=unID+1 ! Moving
HOTSPOT 0, 0, 0, unID, ang, 6 : unID=unID+1 ! Centre
HOTSPOT 1, 0, 0, unID, ang, 7 : unID=unID+1 ! Reference
DEL 1

I can’t test this right now, but it should be something like this.

Ahh, it works but not how I want it. I want it to rotate around the Y axis. I've managed to get it to rotate that way, however the hotspot doesn't stay in the correct place. Here is my code now

unID = 1
 HOTSPOT 0.2, 0, 0, unID, ang, 4 : unID=unID+1 ! Base 
 HOTSPOT 0.2*COS(ang), 0, 0.2*SIN(ang), unID, ang, 5 : unID=unID+1 ! Moving 
 HOTSPOT 0, 0, 0, unID, ang, 6 : unID=unID+1 ! Centre 
 HOTSPOT 0, 2, 0, unID, ang, 7 : unID=unID+1 ! Reference 

It rotates around the Y axis but the hotspot doesn't stay in the correct place :S

Thanks very much for your help!

[Bruce]

1. Shift the unID = 1 declaration into the Master script.
2. In longer scripts, you will need the ROTY -ang command (in my first example) prior to the hotspots to reset the Base hotspot properly - otherwise your hotspot will just follow your geometry, and reset every time
3. It's also handy to limit your ang in the Parameter script so it behaves logically, i.e. VALUES "ang" RANGE [0, 360)
4. The Z coord for the hotspot needs to be negative in this case.

The below script works for me (it's just my quirk to put the unID=unID+1 statement before the HOTSPOT command):

unID=unID+1 : HOTSPOT 0.2, 0, 0, unID, ang, 4 + 128					!Base
unID=unID+1 : HOTSPOT 0.2*COS(ang), 0, -0.2*SIN(ang), unID, ang, 5	!Moving
unID=unID+1 : HOTSPOT 0, 0, 0, unID, ang, 6							!Centre
unID=unID+1 : HOTSPOT 0, 1, 0, unID, ang, 7							!Reference

ROTY ang

BLOCK 1, 1, 1

DEL 1

[JGoode]

Bruce wrote:
4. The Z coord for the hotspot needs to be negative in this case.

Thanks very much! Out of curiosity, why does the Z coord for the hotspot need to be negative? Very much appreciated!

[Bruce]

It has to do with the direction of rotation in GDL, combined with the ROTY to rotate the geometry. I still get confused over it, but that's the reason.