30 seconds left (Final animation in the animation section)

[Matt]

A scalar is just a single number, a quantity, or a magnitude. If you read up on scalars the definitions are more specific and jargon-laden than that, so I'm not surprised that they are hard to understand, but I think for the sake of understanding what they are in Terragen you should think of a scalar as a number. e.g. 0, 1, 2, 5.6, -10.3, -5, 1 million, etc.

A scalar only becomes a point in space after you multiply it by a vector, but that's because the result is a vector, not a scalar. Often we just deal with scalars, without vectors, so there's no need to think of them in terms of vectors all the time. So, scalar = number.

If you multiply a scalar by a vector (that is to say, multiply a vector by a scalar), the scalar multiplies the length (or magnitude) of the vector to create a new vector. Vectors can represent the difference between two points (i.e. the displacement from one point to the next), and when you multiply such a vector by a scalar it multiplies the length/magnitude of the vector. However, if you are using the vector to represent a point in space then it multiplies the point's distance from the origin, because a point is represented by a vector that takes you from the origin to the point.

Otherwise, a scalar is just a number.

Matt

[TheBadger]

Hannes, like you said, its just a test video. But I noticed that the clouds are moving up from the object, rather than back and away. Maybe that is what should happen. But if so, shouldn't it happen slower?... The upward movement I mean.

Cant wait for the next render man!

[Hannes]

@Matt, thank you so much for your detailed explanation. Maybe a short and very simple tutorial where scalars and other things like that are used would be nice for those like me who have difficulties with those abstract things.

@Badger, actually the clouds and their density shaders aren't moving at all. The only thing that moves is the asteroid. So the clouds stay in place which is what I want. There is no reference point for the movement since the earth is hidden for testing purposes, but right now I am rendering another test animation (a bit larger and longer), which shows the earth and hopefully the correct behavior of the trail.

[Hannes]

First of all:
@rat: I forgot to say thank you for your efforts, sorry! I liked what you did. What did you use in PS?
@TU: funny! What I did is quite exactly what you mentioned some threads before. I used a very similar technique like in my avalanche animation.

Here is another test animation as mentioned. I thought about posting it in the animation section, but it's still part of this thread I think. Maybe the next one.
It's quite noisy and flickering. I used a little time blending in AE to make it a bit smoother.

[TheBadger]

Ahhhhh I see now. Great! It works perfectly, it seems.

Its really fantastic Hannes

I only see one issue. Really not a issue, just a observation. And that is the comet is far outside the Exosphere, but comets don't burn until they reach the Mesosphere.

Ok OK, im being a dick. It does looks great. Never mind me and my back seat driving. 

Still, since I brought it up anyway. How hard is it to move that death star around anyway?
How hard will it be for you to render the shot your showing now, then a shot form deeper in the atmo, then a shot from ground looking up as its coming in?
Would you just copy your nodes and then put in new coordinates, or just move the camera, or what? Is it hard to work with?

Some info you may want, depending on how far you decide to take this.
http://www.srh.noaa.gov/jetstream/atmos/layers.htm

take a break if you need Hannes, but don't abandon this one. Its freaking cool!

edit*
Sorry, last question... Is the planet/comet object rotating? I thought it was. But now I think its just an effect of the camera moving...
Can the object be set to rotate on its axis? I remember lots of discussion on this in the forum, but cant remember what the conclusion of those threads were.

[Hannes]

Hey Badger, thanks again!
The issue you mentioned came into my mind too. Call it artistic freedom. I'll let it burn for the same reason you can hear loud explosion sounds in space in almost every sci fi movie. 

The asteroid isn't rotating. I guess it would be possible to just animate the rotation, but in this case the trail's localised clouds have their coordinates on the planet, so they would follow the rotation too, which is not wanted. A solution would be to create a non renderable not rotating planet for the trail and an identic one that's rotating and renderable, but not connected with the trail.
At least in theory...

Moving the asteroid is just like moving any other object. Since it's small enough you can use the handles, which is quite comfortable.
It's quite special to sync the trail with the asteroid. They move automatically with it, but for some reason the coordinates have to be adjusted during the animation.

[TheBadger]

I'll let it burn for the same reason you can hear loud explosion sounds in space in almost every sci fi movie. 

lol! I accept that answer with a huge smile! 

Thanks for answering questions!

[Hannes]

Rendertest with higher quality settings. I disabled GI and used a fill light setup instead. Rendertime for this image: 34 minutes.
Strange artifacts in the orange glow to the left. I don't know if these are really artifacts or parts of the asteroid?! It's still there even with acceleration cache set to none.

[TheBadger]

Looks like a rib cage.

[Hannes]

Indeed! I'll see if this will be neglectable or not. I started the animation with rendertimes of about 11 minutes per frame, since the earth, which takes longer to render, is not yet visible.

[Tangled-Universe]

Thanks Matt, of course very useful!

I was wondering a few things:

A scalar is just a single number, a quantity, or a magnitude. If you read up on scalars the definitions are more specific and jargon-laden than that, so I'm not surprised that they are hard to understand, but I think for the sake of understanding what they are in Terragen you should think of a scalar as a number. e.g. 0, 1, 2, 5.6, -10.3, -5, 1 million, etc.

Ok clear.

A scalar only becomes a point in space after you multiply it by a vector, but that's because the result is a vector, not a scalar. Often we just deal with scalars, without vectors, so there's no need to think of them in terms of vectors all the time. So, scalar = number.

This is where I get in trouble, because in my search for math-wisdom to figure out differences between scalars and vectors I come across multiple sources which clearly state:
Scalar = vector without direction.

So my question is simple: are those sources wrong or is TG using a different definition?

The definition you gave does explain why scalars and colours are interchangeable in certain parts of the node network, as colour also allows you to specify a number.
This doesn't answer my question of course, since this only describes the implementation of these principles in TG.
It's just to see if I can get my new way of understanding it now being confirmed.

If you multiply a scalar by a vector (that is to say, multiply a vector by a scalar), the scalar multiplies the length (or magnitude) of the vector to create a new vector. Vectors can represent the difference between two points (i.e. the displacement from one point to the next), and when you multiply such a vector by a scalar it multiplies the length/magnitude of the vector.

Say I want to multiply a vector with a scalar, do I use a multiply vector node or a multiply scalar node or does that not matter?

(edit: there's something in the docs about data type conversion that should answer it I believe/hope)

However, if you are using the vector to represent a point in space then it multiplies the point's distance from the origin, because a point is represented by a vector that takes you from the origin to the point.

This confuses me, because it implies that there are other ways of representing a point in space than a vector?
My belief was a scalar, but as you may know by now I don't know it anymore

Consequently, I don't understand the "however", because to me it's the same as the first part of that paragraph.
I don't understand the difference you're explaining.

I hope you find some time to explain some of these ultra-basic things.
Thanks in advance

Martin

[Hannes]

OK, thanks guys, now I'm completely confused!
I'm so glad that I didn't have to use the blue nodes...

[j meyer]

Very nice Animation test.
Go,Hannes,go!

[Matt]

A scalar only becomes a point in space after you multiply it by a vector, but that's because the result is a vector, not a scalar. Often we just deal with scalars, without vectors, so there's no need to think of them in terms of vectors all the time. So, scalar = number.

This is where I get in trouble, because in my search for math-wisdom to figure out differences between scalars and vectors I come across multiple sources which clearly state:
Scalar = vector without direction.

So my question is simple: are those sources wrong or is TG using a different definition?

I have never seen a scalar described as a vector without direction. A scalar is not a vector.

If you multiply a scalar by a vector (that is to say, multiply a vector by a scalar), the scalar multiplies the length (or magnitude) of the vector to create a new vector. Vectors can represent the difference between two points (i.e. the displacement from one point to the next), and when you multiply such a vector by a scalar it multiplies the length/magnitude of the vector.

Say I want to multiply a vector with a scalar, do I use a multiply vector node or a multiply scalar node or does that not matter?

(edit: there's something in the docs about data type conversion that should answer it I believe/hope)

You would use a Multiply Vector. With most function nodes in Terragen, the last word in the name of the node (here it is 'vector') tells you what datatype the node outputs. When you multiply a scalar by a vector you want to output a vector, so use Multiply Vector.

However, if you are using the vector to represent a point in space then it multiplies the point's distance from the origin, because a point is represented by a vector that takes you from the origin to the point.

This confuses me, because it implies that there are other ways of representing a point in space than a vector?
My belief was a scalar, but as you may know by now I don't know it anymore

Consequently, I don't understand the "however", because to me it's the same as the first part of that paragraph.
I don't understand the difference you're explaining.

I hope you find some time to explain some of these ultra-basic things.
Thanks in advance

I'm not the best teacher of this stuff. Try this:

http://www.sparknotes.com/testprep/books/sat2/physics/chapter4.rhtml

You can step through all the sections of this chapter using the "CONTINUE TO THE NEXT SECTION>>" link below the text.

Matt

[Matt]

However, if you are using the vector to represent a point in space then it multiplies the point's distance from the origin, because a point is represented by a vector that takes you from the origin to the point.

This confuses me, because it implies that there are other ways of representing a point in space than a vector?
My belief was a scalar, but as you may know by now I don't know it anymore

Consequently, I don't understand the "however", because to me it's the same as the first part of that paragraph.
I don't understand the difference you're explaining.

My sentence wasn't very clear.

A vector can be used to represent a point, or it can mean other things. I was trying to say that if your vector is a point (e.g. "Get position"), then multiplying that vector by a scalar moves the point further away from the origin or closer to the origin, but it always stays somewhere on the same line from the origin to the point. The line is infinite in both directions. I should also say that if you multiply by a negative scalar, the direction of the vector is reversed, so the point ends up on the opposite side of the origin, but it's still somewhere along the same infinite line.

Matt