Heightmaps and other planetary data

Alright, this topic shall now serve for the discussion about planetary data and the Space Engine. For now, we can look for some whitepapers and other documents on how it's done.



One way is to do it like Kerbal Space Program: six quadtrees mapped into a cube. Also, some sources mention a spherical version of the ROAM algorithm, but I have had no luck finding it yet.

I think it Will Be Awesome in our game

Quote :

One way is to do it like Kerbal Space Program: six quadtrees mapped into a cube. Also, some sources mention a spherical version of the ROAM algorithm, but I have had no luck finding it yet.

Right. I've written a quadtree algorithm, but making one a neighbor to another is tricky.

I'm not sure how to iterate through the triangles in the ROAM algorithm with any decent framerate. (That's a lot of triangles to be performing distance checks on.)

roadkillguy wrote:

Quote :

One way is to do it like Kerbal Space Program: six quadtrees mapped into a cube. Also, some sources mention a spherical version of the ROAM algorithm, but I have had no luck finding it yet.

Right. I've written a quadtree algorithm, but making one a neighbor to another is tricky.

I'm not sure how to iterate through the triangles in the ROAM algorithm with any decent framerate. (That's a lot of triangles to be performing distance checks on.)

This seems fairly simple. Is there a limit to resolution? Also, I don't want to bother you guys about this, but I do feel the need to ask if anyone has ever done things such as overhangs. They would obviously require something more than this regular system. I figure that slopes of a certain angle could be further subdivided and then noised (up from the plane of the slope) to create rock faces that overhang the slope. I don't want you guys to really worry about it, but it is something to think about.

That's ok Rex, thanks for the bunny.

We can potentially have overhangs, but that would be extremely complicated. A quadtree makes that impossible. We would have to make the planet out of voxels, but that would require so much memory it's not even funny. Rendering over the surface of voxels = blech.

*Takes out Vorpal sword and slays voxel*
Feel better now, Roadkill?

That's about as useful as I am for this thread, but the linked picture looked awesome.

roadkillguy wrote:

We can potentially have overhangs, but that would be extremely complicated. A quadtree makes that impossible. We would have to make the planet out of voxels, but that would require so much memory it's not even funny. Rendering over the surface of voxels = blech.

oK. Just wondering if that would be too difficult. I can see how it would get complicated easily, given that you would then have two or three vertices on a ray going from the center out.

Using that method, you would then have to somehow define which vertices were attached to which. Procedurally? Very difficult.

Using a voxel engine also often creates little floating pieces of terrain (just like in minecraft). Height maps should be sufficient.

roadkillguy wrote:

Using that method, you would then have to somehow define which vertices were attached to which. Procedurally? Very difficult.

Using a voxel engine also often creates little floating pieces of terrain (just like in minecraft). Height maps should be sufficient.

That's what I'm trying to say, basically.

Sweet. Just found this.

roadkillguy wrote:

Sweet. Just found this.

That... Looks... Helpful...
*Gets to end, notices link*
It was used IN SPORE!!! RRAAAAAWWWRR!!!

Huff... Huff...

Anyway, I know Roadkill will be able to use it to make realistic planets, even if Maxis couldn't do that with a whole team of developers IN SPORE!!! RRAAAAAWWWRR!!!

Huffff...

So yes, this looks like it will do nicely, even if it was used in you-know-what. And it works with LOD!

Just read through it. It's pretty nice, but unfortunately unfinished - it does not have anything about texturing the landscape and so forth. Still extremly useful, though.

roadkillguy wrote:

Sweet. Just found this.

Brilliant.

This went over my head like a flying bowl of petunias, but the bit I understood was awesome.

The Uteen wrote:

roadkillguy wrote:

Sweet. Just found this.

That... Looks... Helpful...
*Gets to end, notices link*
It was used IN SPORE!!! RRAAAAAWWWRR!!!

Huff... Huff...

Anyway, I know Roadkill will be able to use it to make realistic planets, even if Maxis couldn't do that with a whole team of developers IN SPORE!!! RRAAAAAWWWRR!!!

Huffff...

So yes, this looks like it will do nicely, even if it was used in you-know-what. And it works with LOD!

?? what are you talking about?

It under references, a link to Maxis saying how they used this to make their planets. Not that they were any good of course.

I also mentioned my confidence in your abilities.

The Uteen wrote:

It under references, a link to Maxis saying how they used this to make their planets. Not that they were any good of course.

I also mentioned my confidence in your abilities.

To quote the late Bashi, "Spore did a most of the technical stuff quite well, it was the gameplay that was the issue."

Now, in any case, I was wondering when you might be able to give me a rough estimate on our planets' scales? How much smaller than Earth will a purportedly Earth-sized world be? Just need the info for my work on Society Stage and the like.

roadkillguy wrote:

The Uteen wrote:

roadkillguy wrote:

Sweet. Just found this.

That... Looks... Helpful...
*Gets to end, notices link*
It was used IN SPORE!!! RRAAAAAWWWRR!!!

Huff... Huff...

Anyway, I know Roadkill will be able to use it to make realistic planets, even if Maxis couldn't do that with a whole team of developers IN SPORE!!! RRAAAAAWWWRR!!!

Huffff...

So yes, this looks like it will do nicely, even if it was used in you-know-what. And it works with LOD!

?? what are you talking about?

Ahh ok. There's basically no other way to do dynamic LOD on a sphere. Really the only thing that I got from that article is that normalizing the vertex coordinates of a cube is sufficient to space the vertices on a sphere. Please look that up. It's really basic vector stuff. This method is a lot better spacing wise than a traditional lat/lon sphere.

Regarding size of planets, I would say small ones would be spore sized, and large ones could be 10x bigger. That's my estimate (and goal) but we might be able to tweak them bigger. (It really just depends on performance) I'd love to add support for gas giants too, which wouldn't even need to use this spherical LOD, just a dynamic fog thing. They could be MUCH bigger, and we can still have hydrogen cores and stuff just for fun. I'll make stars, but because they don't have solid mountains they'll be traditional spheres with jets of flame that will melt your ship. Easy. In the future I'll add rings too.

So yeah [1-10]x spore planets is my goal. To keep things in the universe proportional, I might say that a planet the size of earth would have to be 2xspore. Really, I don't think it will matter because we'll be simulating life on these planets too.

roadkillguy wrote:

Regarding size of planets, I would say small ones would be spore sized, and large ones could be 10x bigger. That's my estimate (and goal) but we might be able to tweak them bigger. (It really just depends on performance) I'd love to add support for gas giants too, which wouldn't even need to use this spherical LOD, just a dynamic fog thing. They could be MUCH bigger, and we can still have hydrogen cores and stuff just for fun. I'll make stars, but because they don't have solid mountains they'll be traditional spheres with jets of flame that will melt your ship. Easy. In the future I'll add rings too.

So yeah [1-10]x spore planets is my goal. To keep things in the universe proportional, I might say that a planet the size of earth would have to be 2xspore. Really, I don't think it will matter because we'll be simulating life on these planets too.

Okay, so there won't really be that much room for nations, and we'll need to call on careful planning and suspension of disbelief to make them work just right.

Thanks!

roadkillguy wrote:

roadkillguy wrote:

The Uteen wrote:

roadkillguy wrote:

Sweet. Just found this.

That... Looks... Helpful...
*Gets to end, notices link*
It was used IN SPORE!!! RRAAAAAWWWRR!!!

Huff... Huff...

Anyway, I know Roadkill will be able to use it to make realistic planets, even if Maxis couldn't do that with a whole team of developers IN SPORE!!! RRAAAAAWWWRR!!!

Huffff...

So yes, this looks like it will do nicely, even if it was used in you-know-what. And it works with LOD!

?? what are you talking about?

Ahh ok. There's basically no other way to do dynamic LOD on a sphere. Really the only thing that I got from that article is that normalizing the vertex coordinates of a cube is sufficient to space the vertices on a sphere. Please look that up. It's really basic vector stuff. This method is a lot better spacing wise than a traditional lat/lon sphere.

Regarding size of planets, I would say small ones would be spore sized, and large ones could be 10x bigger. That's my estimate (and goal) but we might be able to tweak them bigger. (It really just depends on performance)

Given gravitational forces, there has been a predicted limit to the size of rocky planets, which I shall go look up.

According to this paper (figure 4) the maximum size for a planet of earth-like composition is about 2.5x earth's radius, whereas the limit to the size of a planet that is a giant ball of ice is about 4x earth's radius. Any planet we work with will be limited to about 3.5 earth radii, but at that mass (possibly over 1000 times the mass of earth) complex multicellular life will be highly unlikely due to gravity

Back to that figure 4, we can see that the planets we're looking at will be the ones represented by red, green and dark blue lines.

Let's estimate the gravity on planets of different radii.

The volume of a planet with 1 earth radii is 4.1887
for a planet with 2 earth radii, it's 33.5103
for a planet with 3 earth radii, the volume is 113.0973

These numbers are maximums, and estimates, but they give us a good groundwork.

Size (earth radii)	earth volumes	mass (earth masses)	density (compared to earth)	gravity
1	1	1	1	1
2	8	5	1.6	3.2
3	27	10.5	2.6	7.8

So a planet 3x earth's radius could have as high as 7.8 gs, which would make life pretty difficult. So I'll cut off our planet size at about 2 earth radii, just so that we don't have to worry about extremely high gravity planets.

Sorry for the double post, but what would the maximum resolution for terrain? Around 1m²?

~sciocont wrote:

Sorry for the double post, but what would the maximum resolution for terrain? Around 1m²?

If we end up using space engine we should be able to do that (see third paragraph):
http://spaceengine.ucoz.ru/blog/detail_textures_on_planets/2011-07-30-1

Dr_Chillgood wrote:

~sciocont wrote:

Sorry for the double post, but what would the maximum resolution for terrain? Around 1m²?

If we end up using space engine we should be able to do that (see third paragraph):
http://spaceengine.ucoz.ru/blog/detail_textures_on_planets/2011-07-30-1

Yes It will help us

BTW
I just Opened A topic About Making Textures LOL