Cloud shadows still buggy

[t00fri]

I carefully checked my 64k Earth setup with the latest CVS compilations in two configurations:

a) RGB base + Spec texture in ONE RGBA arrangement. VT tiles 1kx1k of this. Tile resolutions latitude optimized, of course.

b) Separate 1kx1k tiles of RGB base texture and Spec texture. That's the 'canonical' setup for most people (ignoring how to assemble RGB+Spec into RGBA).

Again tile resolutions are latitude optimized.

In case a) (which is more storage economic), things run fine both for Linux and Windows and with cloud shadows both ON and OFF. My cards have 256MB RAM each. The system RAM is 3GB for Linux and 2GB on my Windows notebook.

+++++++++++++++++++++++
Case b) crashes BOTH for Linux and Windows if cloud shadows are ON. For Windows I get the familiar red ball. Linux just crashes.
+++++++++++++++++++++++

In any case this situation is unsuitable for 1.5.0 final!

Bye Fridger

[BobHegwood]

Any more information forth-coming on MOVING cloud shadows?

Just thought I'd ask. I see from a thorough search that this topic
is probably not very high on the list of things to be done, but it would
be very nice at some point.

Thanks, Bob

[chris]

Any more information forth-coming on MOVING cloud shadows?

Just thought I'd ask. I see from a thorough search that this topic
is probably not very high on the list of things to be done, but it would
be very nice at some point.

Thanks, Bob

Cloud shadows do currently move with the clouds, if that's what you mean. Or are you asking about cloud shadows that move with changing sun direction? I've come up with a technique that might work for that and that doesn't require reprojecting clouds onto a cube map.

--Chris

[t00fri]

I thought in the present CVS code cloud shadows were deactivated!? In fact, I cannot make out ANY differences in the rendering for shadows ON|OFF...

Bye Fridger

[BobHegwood]

Hence my question...

[chris]

I thought in the present CVS code cloud shadows were deactivated!? In fact, I cannot make out ANY differences in the rendering for shadows ON|OFF...

They're not deactivated. However, they will only work if you are using textures that are smaller than your graphics cards max texture size (i.e. 4k x 4x for your GeForce 5900.) A future implementation will remove this limitation.

--Chris

[BobHegwood]

If I may...

Is the implementation method still restricted to alternate textures?

In other words, is there still no other way to implement the cloud
shadows within Celestia itself? Can't add a line to the solarsys.ssc
file?

Feature request?

Thanks, but I've been away for a while, Brain-Dead, Bob

[chris]

If I may...

Is the implementation method still restricted to alternate textures?

In other words, is there still no other way to implement the cloud
shadows within Celestia itself? Can't add a line to the solarsys.ssc
file?

Feature request?

Thanks, but I've been away for a while, Brain-Dead, Bob

Some people did make static cloud shadows using--I think--the overlay texture. But, these cloud shadows didn't move as the clouds rotated. As of 1.5.0, cloud shadows are 'automatic', subject to the restrictions I mentioned in my response to Fridger. You click a check box and cloud shadows are enabled--no need to mess with solarsys.ssc.

Aside from the restrictions on texture size, the problem with cloud shadows as currently implemented is that they are faked--the shadow appears directly under the cloud, regardless of where the sun is in the sky. This is sort of ok because the height of the clouds above the surface is small relative to the size of the planet.

--Chris

[Cham]

The clouds shadows aren't working at all on my Mac. Turning ON the shadows option gives some painfully slow dark rendering on the planet. Especially when the clouds are a large texture (as in the case of Earth). I think we need an option at the SSC level to tell Celestia to not render the shadows for this or that planet.

[t00fri]

I thought in the present CVS code cloud shadows were deactivated!? In fact, I cannot make out ANY differences in the rendering for shadows ON|OFF...

They're not deactivated. However, they will only work if you are using textures that are smaller than your graphics cards max texture size (i.e. 4k x 4x for your GeForce 5900.) A future implementation will remove this limitation.

--Chris

I was aware of this restriction.

My clouds are my old 2k x 1k ones and I use 1k x1k VT's. Nothing is bigger than that. Also some time ago, the cloud shadows worked for me (badly though).


Bye Fridger

[chris]

The clouds shadows aren't working at all on my Mac. Turning ON the shadows option gives some painfully slow dark rendering on the planet. Especially when the clouds are a large texture (as in the case of Earth). I think we need an option at the SSC level to tell Celestia to not render the shadows for this or that planet.

Still? Cloud shadows have been greatly simplified since the original implementation.

I don't want to add an SSC switch to control cloud shadows: there's either a driver bug or a Celestia bug here, and in neither case is it worth adding an ssc option as a workaround.

--Chris

[chris]

I thought in the present CVS code cloud shadows were deactivated!? In fact, I cannot make out ANY differences in the rendering for shadows ON|OFF...

They're not deactivated. However, they will only work if you are using textures that are smaller than your graphics cards max texture size (i.e. 4k x 4x for your GeForce 5900.) A future implementation will remove this limitation.

--Chris

I was aware of this restriction.

My clouds are my old 2k x 1k ones and I use 1k x1k VT's. Nothing is bigger than that. Also some time ago, the cloud shadows worked for me (badly though).

The fact that you are using a VT for the Earth's surface is the reason you're not seeing in cloud shadows. Sorry--I realized that I wasn't clear at all about which textures needed to be <= 4k x 4k: it's *both* the cloud texture and the surface textures. After 1.5.0, I will be changing the cloud texture code to remove the size restriction for surface textures, though the requirement for cloud texture size will remain.

So everyone knows what to expect, here's a demonstration of cloud shadows with Don Edward's 8k DDS cloud texture:

Cloud shadows on:


Cloud shadows off:


Note that only DX10 capable graphics hardware like the GeForce 8xxx series and the Radeon X2xxxx series are capable of using 8k textures, but you can get similar results with older hardware and a 4k cloud map. In order to really see the effect of the shadows, it's important to have a higher resolution cloud map than the 1024x512 default texture. Also, the effect is only noticeable from lower altitudes; from distant viewpoints, the clouds hide their own shadows.

--Chris

[Cham]

Actually, I just remade the clouds test on the Earth (with the 8k clouds texture) and I got nothing : no shadows at all.

It's just not there.

[chris]

Actually, I just remade the clouds test on the Earth (with the 8k clouds texture) and I got nothing : no shadows at all.

It's just not there.

That's expected with your hardware and an 8k cloud texture--see this remark:

Note that only DX10 capable graphics hardware like the GeForce 8xxx series and the Radeon X2xxxx series are capable of using 8k textures,

For older hardware, Celestia has to split an 8k x 4k texture, at which point it becomes impossible to compute cloud shadows. For your graphics card, I think you need to use a 2k texture. NVIDIA cards have supported 4k textures since the GeForce FX series, but only very recent ATI cards have this capability.

--Chris

[Cham]

Chris,

it doesn't work on Mars either, where I use a 2k X 1k clouds texture. Turning ON the shadows doesn't change anything. No shadows.

[chris]

Chris,

it doesn't work on Mars either, where I use a 2k X 1k clouds texture. Turning ON the shadows doesn't change anything. No shadows.

Only two things that I can think of:

- The effect with the Martian clouds is so subtle that it's barely noticeable (this will naturally be the case with very thin clouds)
- Or, you have a high resolution surface texture (> 2k) for Mars

--Chris

[Cham]

- Or, you have a high resolution surface texture (> 2k) for Mars

This is the case. But then, I don't understand what textures I should use to see proper shadows. Why is the base texture resolution should be related to the clouds texture ?

EDIT : I just tested a gas giant with clouds, and the shadows are there. But they are very ugly and the planet looks unatural. I'm unable to tell if the shadows rendering is right, or if there's something wrong in this case. I suspect the rendering is okay, except that it's ugly. The rendering is much better, in this case, without the shadows. So this is why I'm asking for a shadows switch at the SSC level.

Suppose I have some new hardware which is able to show the shadows in all cases. I want to keep the nice shadows for the Earth, but don't want to see the ugly shadows on my gas giant. Without the shadows switch in the SSC, I'm forced to have those ugly shadows in many cases, and nice shadows in other cases. This is bad ! We need that SSC switch.

[chris]

- Or, you have a high resolution surface texture (> 2k) for Mars

This is the case. But then, I don't understand what textures I should use to see proper shadows. Why is the base texture resolution should be related to the clouds texture ?

It's a limitation of the current technique for computing cloud shadows. It will be lifted after 1.5.0.

--Chris

[Cham]

Chris, please read again my previous message (cross posting...). I edited the message.

EDIT : and there's also a consistency point : we already have a kind of "switch" at the SSC level, for the bump map (and normal map), in the case of the base texture. It's a similar thing for the clouds shadows. We should have a shadow "switch" in the SSC too.

Actually, I think that we should have more control in the SSC, on how the rendering should be done.

[BobHegwood]

Well, I hate to throw a rotten egg at you all here, but I haven't seen
a cloud shadow since I've been using Celestia. This is why I opened
this can of worms again.

Sorry, but my 8400 GS can display 8k textures, and I have the box
checked under view options, but I still see nothing that indicates to
me that there are cloud shadows available.

Sorry I brought it up now. The point I'm really having though,
is how do I define these cloud textures to BE cloud textures.
Where in the SSC? do I define a texture as a cloud texture?

Does this question make sense?

Take care, Brain-Dead