Understanding rotations in Carrara

stitlown

Hi Guys,

For a number of years, I've used Carrara to film a fly into and then fly out from space to the earth's surface to "locate" where a particular video is set.  I have always had troubles getting the planet/sphere rotations just right because I find the Carrara rotations totally unintuitive and it has a habit of swapping numbers between axes and values when it thinks it knows better than me.  I finally thought I'd cracked it and so decided to do a fun video of the earth in space from a number of different lattitudes.  To achieve this I had to do some wierd rotations but I thought it made some sort of weird geometric sense.  However, late last night admining my work, I realised that the rotations were still wrong - ok over the equator and looking almost ok at the tropics but clearly wrong, wrong, wrong at the arctic / antarctic circles.

So this morning I set out to rectify and started to try and get the poles right first - but have failed miserably.  Frustrated, I loaded up DAZ Studio where the gui is friendlier for experimentation and started plyaing.  In Daz Studio, it is super easy and perfectly intuitive.  A sphere created with its hot point at its center can be made to rotate around any chosen lattitde circle with just with y-rotation (sphere created with y+ as the main axis) and the x-rotation dialled (fixed number) to the chosen lattitude.  The only quirk is that longitude 0 is y-rotate 180 but that is a feature of the earthmap construction.   This works all the way from the equator to the poles.

Is there anybody out there who can explain to me how carrara rotations work and why it is not as simple as Daz Studio; and if you are so inclined how I could set up my spheres to do what I want.  FWIW, the dud video is here on youtube (for the time being) https://youtu.be/09JYaMIq4oU

Also FWIW, the rotations I used in that vid are:z-rot for the axis spin.   x-rot/y-rot 0/0 for equator, 0/33.3 @0 and 360 degrees (realised I've got that wrong, should be 23.5) 16.65/-16.65 at 120 degrees; and -33.3/0 at 240 degrees  for the tropics- double those values for the arctic / antarctic. 

It's possibly academic as I am recreating the scene in D|S and will animate it there where I can get to the outcome I need a whole lot quicker, it appears.

Thanks in advance. Lx

evilproducer

I guess I'm at a loss here. Are you rotating the earth to get your camera view of a certain latitude or moving the camera so that latitude is visible in the camera? Also, are you using the spin modifier?  Could you be accidentally inadvertantly adding keyframes if manually altering the tilt of the earth, which could throw off the rotation? What are you using in the Motion Tab: Quaternian or Angles? I <i>think</i> Carrara defaults to Quaternian. What does Studio default to?

DesertDude

evilproducer said:

What are you using in the Motion Tab: Quaternian or Angles? I <i>think</i> Carrara defaults to Quaternian. What does Studio default to?

Yes, you are right it defaults to Quaternian. Switching to Angles allows for much "free-er" rotation options. For technical explanations, I throw up my hands as I have seemingly read contradictory explanations of what Quaternian actually means. All I know is one of the first things I do when creating new objects is switch them to Angles for peace of mind, perhaps much to my detriment and ignorance.

stitlown

Thanks guys.  I was rotating the earth sphere (5 of 'em in fact) under a stationary camera.  Was not using spin, just animating on the rotation modifiers.  Definitely no aberrant key frames.  Knew nothing of Quaterian or Angles so will go explore (and know very little of spin etc.  I'm and "old newbie" who just muddles through when he has to.)

FWIW, I was able to get the same scene up an rendering in Studio very fast (although generated a bug report along the way - haha) and Carrara's rendering seems much faster than 3Delight.  17 mins per 10secs on this scene in Carrara vs about 38 mins per 10secs in 3Delight.

Off to explore spins and angles. Thanks again.

stitlown

Quick follow up and thanks again guys.  In just some quick playing, "Spin" is the answer, just need to learn how to tune it.  I can manually navigate to the place I want to start and then "spin" on the appropriate axis does exactly what I need - and with way simpler timelineing.

As for Quaterian vs angles, had a play with both.  I sort-of (30 second glance) understood what Quaterian is all about, so basically great for computers etc but difficult for a human to see quickly what parameters .... and I watched both while the spin over the south pole worked out and I can sort-of understand what is happening with the angles (lots of swapping from + to - and angle complements and supplements etc.) but as to understanding the starting angles in either, it is definitely greek to me.  A near-to-the-south-pole in angles (when the equator is 0 / 0 / -151 == approx the equator above Sydney) is approx -97 / -50 / -99.  Could not possibly explain why those angles, but the result is looking down on what anyone but a pedant or accuracy freak would think was the South Pole.  But very different numbers would be needed in all 3 if I wanted to start say at the longitude of Rio!

Cheers, Lx

evilproducer

The spin modifier can be keyframed, so for example you start with the standard 1 spin per second, and two seconds in, you change it to -1, the spin will reverse. The type of tweener you use between those keyframes will determine what that change of direction will look like.

Mistara

teee hee  this was after changing Motion Tab: to Angles

ed3D

Mistara said:

teee hee  this was after changing Motion Tab: to Angles

Question is How to get the Small object to  Orbit around the Big One  ?? ( with two Spheres )   +   Thanx 

WendyLuvsCatz

ed3D said:

Mistara said:

teee hee  this was after changing Motion Tab: to Angles

Question is How to get the Small object to  Orbit around the Big One  ?? ( with two Spheres )   +   Thanx 

move the hotpoint (Capslock) 

Dartanbeck

Center both spheres in the same place (x,y and z)

Create a Target Helper Object and center it in the same location - do not parent it to either sphere

Place the orbiting sphere into this Target Helper and then with only the sphere selected, move it out to where it's orbit sould be

Now the outer sphere can orbit the center sphere by rotating (or spinning) the Target Helper object independently from the center sphere, which can spin away however it needs to.

 

If we want this aparatus to orbit something else:

Make another Target Helper Object and drop all of this into it. Make another Target Helper Object and center it on what these two spheres are supposed to orbit and drop the THO which contains the aparatus into this one. Now the aparatus can freely orbit whatever.

 

See DCG's (now free) Cognito plugin for more sophistication!

Dartanbeck

So for Earth, we'd have a sun, the Earth, and the moon.

1. Let's make all of the necessary spheres in the same place: 0.00x, 0.00y, and 0.00z
2. Rename them to Sun, Earth and Moon respectively
3. We'll scale them for our scene so we can easily identify which is which visually once we move them around
4. Hide the sun sphere so all we can see is Earth (the moon still trapped inside)
5. Create a Target Helper Object through the menu so it ends up at 0, 0, 0, like the others
6. Rename the Target Helper to: Lunar Orbit and then drop the Moon sphere into it (parent)
7. Create a new Target Helper Object and name it: Earth's Orbit and then drop both Earth and Lunar Orbit into it 
8. Select Lunar Orbit and maneuver it out to it's appropriate orbit considering our scene
9. Make the Sun visible again and maneuver the Earth out to where it should be, leaving "Earth's Orbit" centered with the Sun

 

Now the moon can orbit the Earth and use a Point-At modifier to keep the Dark Side away from Earth's view at all times

Earth, with the moon orbiting it, can now orbit the sun using Earth's Orbit

 

We can similarly animate the rest of the solar system in this same manner.

Edit for mistake: We also need Earth to be in it's own Target Helper Object, which contains both Earth and Lunar Orbit