The GCat model of the Solar System

[GCat]

I was messing with the idea of building a fully functional and realistic solar system!

The first stage was getting the proportions of the planets right. I thought that the early result is quite interesting as it shows us just how small planet earth is. Thought I’d share it for its educational value… (We’re on the third planet from the sun incase people weren’t sure)

Diameter of sun = 1,400,000km
Diameter of earth = 12,000km

[EDIT: I used the following way of getting the proportions right:
1 blender unit = 100,000km
For the sun I added a sphere and scaled it to 14x its original size, for earth I decreased it to 0.12.
On reflection I’m not 100% sure this is right because I’m not sure whether the size values refer to diameter of a sphere, its circumference or volume.
Does anyone know if I was right?]

[btw, I’m struggling with mapping photos of planets onto spheres. I’m about to read a bit more on this subject, but if anyone has any quick solutions I’d be interested to hear]

[anogarlr]

I like the idea. It’d make for a neat animation when you’re done. Keep it up.

[digital_me]

I tried this once. And I failed. :x
But don’t get discouraged!
[extreme optimism]If anyone can do this, you can![/extreme optimism]

d_m

[orion119net]

yea, i tryed it too, and failed. good luck(i mean it)!

[fudje]

I presume those aren’t meant to be the actual distances of the planets… Of course, in an accurate model with a realistically sized lens, by the time you managed to be able to have all the planets in shot something is going to be invisible.

[Blendfreak]

try searching the length it takes for the planets to go around the sun. For earth its 365. You can let it go around in 36.5 frames. When you repeat it the planets go around properly. You also need to know how long a day takes on the planets. The hard part is getting the starting position of the planets right.

[GCat]

thanks for comments folks. Sounds like a few of you have begun the same sort of project and given up / got bored! Well, maybe the same fate awaits GCat.

fudje: you are right. Those aren’t distances between planets but the (equatorial) diameter of the sun / planet. And yes, I already tried setting the distances between planets using the scale 1 blender unit = 100,000km. Result: planets = invisible dots and the spaces between planets is vast. So much so infact that I can’t zoom out in Blender to see the entire scene. I’ll have to use a different scale for the distances.

Blendfreak: now I’ve got the relative sizes ok (I think), the next step is to get the individual planetary rotations correct. After that I’ll have a go with the orbit time and orbital path for each planet. Am attempting a systematic approach

Back to work now

[GCat]

quick update on progress.

Because there have been several comments about people having tried this before but not finished the project, I thought it might be useful to leave a note about the process as I develop the model. It’s also turning out to be very educational so I thought I’d include some details of what I’m finding out about our solar system. Here’s where I’ve got to so far:

1. Size: there are 2 important size considerations.

a) The relative sizes of the planets and sun
b) The relative distances between the planets and the sun
It is very difficult / impossible to use the same scale for both size of planet and distance between planets. Therefore I have decided to use 2 different scales (For planet size I am using 1 Blender Unit = 100,000km)

Educational bit: the 4 planets closest to the sun (Mercury, Venus, Earth and Mars) are of a similar size (5,000km - 13,000km diameter). The next 4 planets (Jupiter, Saturn, Uranus and Neptune) are called “Gas Giants” and they range in size from 48,000 - 142,000km diameter). Pluto is an anomaly

2. Time: sorting out time is pretty complicated!! You have to begin with considering the number of frames per second and the length of the animation. There are 2 time-related animation issues:

a) The length of time that each planet takes to do a single rotation (Earth = 24 hours)
b) The length of time that each planet takes to orbit the sun (earth = 365 days)

As with distance, it is very difficult to make an (interesting / educational) animation using a single timescale. So far I have worked on the planets rotation about its own axis and have decided to do the following:

Frames per second = 20
1 earth day = 20 Blender frames = 1 second
All other planets IPO curves were set relative to this
IPO curve for “RotZ”: interpolation set to “linear”, extrapolation set to “cyclical”

Educational bit:

Which planet has the longest day?..

…[Edit]Venus: which takes 243[/edit] earth days to do a full 360 degrees rotation about its axis. [edit]Venus’s day is longer than Venus’s year[/edit]

Which planet has the shortest day?

Jupiter takes just under 10 hours to complete a 360 degree rotation about its axis! **********!!! Has anyone noticed how big this planet is?

3. Mapping an images to a sphere: I’ve found out a bit more about this. As far as I can make out, UV mapping is the solution.

[Demonghast]

Pluto has a decaying orbit I believe. It is predicted that it will leave the suns orbit and leave our solar system after some time. I’m a bit curious if you will be using a circular orbit or an elipse?

I guess after you get the planets done then you can start on the moons, comets and an asteroid belt
Best of luck with this project. It would be really nice to see it finished.

[GCat]

thanks for encouragement Demonghast.

My reference on pluto tells me that it was discovered in 1930, that it has an unusual orbit which takes it inside the orbit of neptune, that it takes the longest time to orbit the sun (248 earth years) and that it has only recently (in 1978) been discovered to have a moon (which is called Charon) and which is half the size of pluto.

It is suspected that another planet exists beyond Pluto.

[Rhysy_2]

I don’t see why you’re having difficulty mapping textures onto spheres. Just go here :
http://gw.marketingden.com/planets/planets.html
Then just use the sphere button. Simple !

Good luck with your virtual orrey

[orion119net]

@Rhysy 2

I don’t see why you’re having difficulty mapping textures onto spheres. Just go here :
http://gw.marketingden.com/planets/planets.html

very good site. ive used some of those textures and theyre very good.

[GCat]

big thanks rhysy2. Jupiter is mapped!

[shadowman99]

You need to see Celestia:

http://www.shatters.net/celestia/gallery.html

Celestia is a free (open source) real-time space simulation that lets you experience our universe in three dimensions. Unlike most planetarium software, Celestia doesn’t confine you to the surface of the Earth. You can travel throughout the solar system, to any of over 100,000 stars, or even beyond the galaxy. All travel in Celestia is seamless; the exponential zoom feature lets you explore space across a huge range of scales, from galaxy clusters down to spacecraft only a few meters across. A ‘point-and-goto’ interface makes it simple to navigate through the universe to the object you want to visit.

[Fonix_Wircs]

[btw, I’m struggling with mapping photos of planets onto spheres. I’m about to read a bit more on this subject, but if anyone has any quick solutions I’d be interested to hear]

Use this place for your textures:
http://gw.marketingden.com/planets/planets.html

Make a UV sphere for the planet, Add material (tex image=Planet texure) then in the material button map it to sphere it may come out crooked but rotation should fix that.

<Edit>
oops just realised rhys fixed that problem, but here ya go anyways…

[GCat]

shadowman99: thanks for pointing out Celestia - amazing site

Fonix Wircs: thanks also for tips - this was a bit of a problem earlier, but I think those images have helped heaps.

Here’s where I’ve got to so far:

The inner solar system:

And The Gas Giants and Pluto

I’ve got a bit of work to do on Saturns rings!
The rotations are OK as far as I can tell
After this I’m going to set up the angle of each axis and then move onto the orbital paths and distances… that’s the plan anyway

Educational bit:
Mercury takes approximately 87 earth days to orbit the sun
Saturn takes 30 earth years to orbit the sun
The average density of earth is more than 5x that of water, whilst the average density of Saturn is less than that of water

[GCat]

progress report - orbits are now set for the planets (set relative to each other). GCat is very exited.

Go to say a big thankyou to S68 for a previous tip he gave about parenting objects to paths.

Here’s a couple of stills from the test animation:

Educational bit:
Venus has some unusual features
Unlike the other planets in the solar system it spins clockwise
Not only that, but it spins very slowly
This has lead some people to conclude that it has been in collision with another object at some point in time
It is a very hot planet (at 600 degrees celcius)
It is covered in thick cloud and atmospheric pressure is massive - similar to being 1km under the sea on earth

= not a good holiday destination

[kirpre]

It looks good so far. One comment that I have is that the planets’ axis should be tilted. I don’t know of any that have a completely vertical axis.

[GCat]

@kirpre

It looks good so far. One comment that I have is that the planets’ axis should be tilted. I don’t know of any that have a completely vertical axis.

Thanks kirpre. Sorting out the tilt is the next stage / challenge(?) of the project. I’m a bit worried that the rotations will get all messed up once I try this.

As far as I can make out, there are three planets with a negligible tilt from the orbital plane:

mercury = 0 degrees
venus = -2 degrees
jupiter = 3 degrees

Neptune has the greatest tilt at nearly 90 degrees

[GCat]

Have worked out the problem of tilting the planets whilst keeping their rotation about the axis. This took some time to work out, so here’s a note on how its done:

Set the rotation of the planet whilst its z axis is parallel to the global z axis
Add an empty
Parent the planet to the Empty
Tilt the empty to whatever angle you need