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interstellar
01-15-2007, 01:27 PM
I'd like to post a thinly-disguised question in the form of a "mini-challenge".

These two pictures represent the nucleus of a comet (the rock) surrounded by its coma (the foggy glow):

http://members.aol.com/INTERSTELL/coma.jpg

The coma is a radial light with fog enabled. Both pictures were made with EIAS but the shadow in the top image was added (in post-production) using Photoshop. The challenge is that a camera will fly through the coma so the shadow must be generated within EIAS. This means the coma cannot be a fog-enabled radial light.

How would you make the rock cast a shadow within an EIAS project? Thanks in advance for your suggestions.

Joe T

richardjoly
01-17-2007, 05:52 AM
Here is something to look into... until someone post the right way to do it.

My test comet shadow (http://www.rdn.qc.ca/eias/comet.mov)

interstellar
01-17-2007, 09:31 AM
Hi Rick,

Thank you for posting your clip. How did you make your coma? Is it a volumetric cloud from someone like Northern Lights or Konkeptoine?

Sincerely,

Joe T

richardjoly
01-18-2007, 01:19 AM
Volumetric cloud plugin?... No, it's a simple sphere. The shadow is an extrusion from the mid part of the comet ending at the end of the sphere. I used a clipping map for the shadow object so it matches the transparency of the sphere edge. That's it. Of course this is not the perfect solution but it would work for far to mid shots.

Here is the project file (http://www.rdn.qc.ca/eias/Project_comet.prj.zip) (The starfield background is in low rez, size does matter...)

interstellar
01-20-2007, 10:32 AM
Hello again Richard,

When we enter the coma in your sample animation, there is a sudden change in the overall appearance as we cross the sphere's boundary. Ideally, the change in brightness would be gradual since the edge of the coma is more transparent than it is near the nucleus. I know your project was a first approximation (thank you for making your project available) but I wonder if anyone can suggest another method for portraying this?

Sincerely,

Joe T

WmH
01-20-2007, 06:28 PM
Hey Joe, this is a simple (old school; no volumetric plugins) method of creating shadows in glows

http://idisk.mac.com/holderness/Public/Concept/comettest1.mov

You cut the shadow by enabling glow in your illuminating light (ie: the sun) and enabling ray, then inverting fog and glow and finally setting the glow intensity to -1 (assuming your primary glow, ie: coma glow light, was 1)

There are a couple things to watch out for: the negative shadow (inverted ray) must match the distance (or slightly less than) of your primary glow field. Extend your negative glow past the glow field and you will rip a hole in the universe;-) (a large white "hole" will appear in your rendered image)

A smoker can be used but again the primary glow and the "negative shadow" settings must match exactly (set up a smoker the way you want it and use the smoker settings unmodified in both the lights (coma and sun) any difference will rip a white hole in your
image where the negative glow light (shadow) differs from the glow
Really simple, once you grasp the mechanics, and renders quickly (that entire animation rendered in about a minute). If you want the project let me know and I'll copy it up. (it took literally 5 minutes to do)

-WmH

interstellar
01-21-2007, 10:47 AM
Hi WmH,

Thank you for posting your recipe and video. I had set up a project based on Richard's method. His recipe worked great until I made my nucleus rotate. My nucleus and its shadow object (a suitably-configured cylinder) could not match perfectly unless I made my nucleus almost perfectly round. My nucleus is irregular in shape, as a true comet nucleus is, so now I'll give your method a try.

I had known about using negative intensities but I've never used them myself. My background is in science and in the real world there is no such thing as light with a negative intensity. I try to remind myself that the digital world is much more flexible. I have to keep telling myself that I'm not really arranging objects in a real-world scene; instead I'm writing lines of code which allows me to do things I could never do in the real world!

See you later,

Joe T

WmH
01-21-2007, 03:24 PM
Glad to help, I played with it a bit (during some idle time I had yesterday) I added a smoker to the glow and pushed the coma back slightly (to account for the push of the solar wind). I am not happy with the (temporal) progression (drift and offset) that I have, it just looks to swirly, but with the smoker in the glow the render time increases substantially and I don't have the time to discover what settings would look right.
It does however look ok in stills.

http://idisk.mac.com/holderness/Public/Concept/comet_3.png

You will need to point the project to your local ubershape plug and bump shader (I didn't include) Turn off the smoker in the sun AND coma glow light to get reasonable render time when you don't need it .
Project file (http://idisk.mac.com/holderness/Public/Concept/comet.prj)

PS I forgot to mention, negative light is a surreal concept to begin with, and this is an inverse use of it (the sun's ray shadow in the glow is inverted to positive and then set to negative illumination) so taking a bit of effort to wrap your head around it is to be expected.

interstellar
01-21-2007, 04:18 PM
Hi WmH,

I threw together a project using your recipe and it works great! For the "sun" light I set the Glow Intensity to -0.5 and the Glow Factor to 2.0. For the "coma" the Glow Intensity is 0.5 and the Glow Factor is 1.4. These values produce a realistic image and they avoid the abrupt disappearance of the shadow at the edge of the coma glow (seen in your original video).

Joe T

WmH
01-22-2007, 02:35 PM
Hi WmH,

I threw together a project using your recipe and it works great! For the "sun" light I set the Glow Intensity to -0.5 and the Glow Factor to 2.0. For the "coma" the Glow Intensity is 0.5 and the Glow Factor is 1.4. These values produce a realistic image and they avoid the abrupt disappearance of the shadow at the edge of the coma glow (seen in your original video).

Joe T
Glad you are getting good results with it, however the shadow edge was likely related to the lights glow extents rather than to intensity or glow factor... I was just quickly scrapping the project together and set the reach of the suns shadow so that is was "for sure" inside the coma glow (as the reverse yields rendering artifacts).

You will find this "trick" sometimes requires fairly precise alignment of the two extents for a believable shadow (primary and negative glow) and that the negative must be "just short" of the primary glow extent or you will get artifacts.

richardjoly
01-22-2007, 04:19 PM
William you are amazing. Always comming up with the right answer... I remember couple months ago with the Storm challenge, your solution was excellent. How many tricks like that do you have up your sleeve...? I knew this shadow in a glow could be done as I have seen it before. The question as where...!

We should bring back an updated tutorials section on the upcoming New Ei Webside: "Old school trick that works perfectly well with recent EIAS version..."

Thanks for sharing your knowledge.

interstellar
01-22-2007, 09:18 PM
I agree with Rick and I owe you one, William. A couple beers, if you're ever in the area (Space Coast of Florida).

I found those artifacts you mentioned; even when the glow regions are precisely set, minor artifacts appear when the Camera is near the juncture of the shadow and the back edge of the coma. However, careful positioning of Camera avoids that and allows me to get a nice "sunrise" off the edge of the nucleus with a dramatic shadow!

Joe T

richardjoly
01-23-2007, 01:48 PM
Joe, would you care to post your final image or animation. Would be a nice conclusion to the thread.

WmH
01-23-2007, 04:17 PM
Thanks for the kind words Richard, I was a heavy user of EI 2.X and spent many nights knocking my head against the CRT. (perhaps why it stuck so long;-) Amazing that many of the old "tricks" still work and still hold up by todays (visual) standards (further proof how amazing EI really is)

No problem for the assistance Joe, just pay it forward; if sometime you see another EI user struggling and (think) you have an answer then take the few minutes to share.
I owe Bear for many hours that I would have spent struggling years ago if not for his always generous assistance.

And I agree with Richard it would be great to see some of the final product.

interstellar
01-24-2007, 09:08 PM
Although it's just a WIP at this time, here's my cometary nucleus. The gas jets erupting from the nucleus are spotlights shining through smokers. I'll probably add several more of these and they'll be animated.

William & Rick, thanks again for your help.

Joe T
http://members.aol.com/astroscans/nucleus.jpg

richardjoly
01-30-2007, 06:54 PM
Theses are great Joe! Thermal expansion and floating debris are a nice touch. Congrats.

halfworld
01-30-2007, 11:35 PM
Exceptional work! I love the tone of the images.

Look forward to seeing more! (We are greedy us users ;)
Ian

interstellar
01-31-2007, 09:54 AM
Richard and Ian, thank you for your nice comments on my images. It may be several weeks before I noodle this project into its final form. I'll try to remember to post something when it is done.

Joe T

WmH
02-07-2007, 12:53 PM
Sorry, been too busy to post. Really nice image(s), hope to see your finished product. Amazing how convincing smokers can be given the current state of the art (for light passing through semi transparent objects).
In my minds eye I had always imagined comets would have been a bit more translucent with some subsurface scattering (like marble or a dirty snowball) but the (few) actual images taken of comets core's show a form very (very) close to your model.
Question: what are the brighter reddish area's in the shadow zone (particularly in image 2), is that glow or translucence or something else entirely?

yhloon
02-07-2007, 04:12 PM
this is the best EI technique I ever seen...
Thanks for sharing! bookmarked

Loon

interstellar
02-10-2007, 07:22 PM
Hi William,

Even though they are largely composed of water ice, comet nuclei aren't translucent in any of the NASA or ESA images I've seen. However, only a handful of comet nuclei have ever been imaged at close range so who knows?

The brighter reddish patches on the "darkside" of my object are meant to be "active" regions on the surface. Today I added a gas jet that erupts from one of those red areas. In reality, the night-side of a real cometary nucleus would probably be as black as coal, but I have to "hollywood-ize" my stuff to keep it lively (thereby keeping my clients happy).

You are right about Smokers; they are very useful. There are eleven in my project so far, and I expect that number to increase.

See you later,

Joe T

interstellar
03-03-2007, 08:42 PM
Hi All,

Here's the update you requested (Ian). I don't have the bandwidth for a nice video, so here's a clunky animated GIF showing every 50th frame of my outgassing comet coma (minus the starfield). There are 18 gas jets (glow lights) each with its own uniquely configured Smoker. A Maya-using friend has already asked for an HDTV rendering of this for possible use in a show.

This wouldn't have been so dramatic without the shadow technique William gave me - thanks again for that!

p.s. I am replacing the animated GIF with a 15fps QT movie.

Sincerely,

Joe
http://members.aol.com/astroscans/comet.mov (http://members.aol.com/astroscans/comet.html)

yhloon
03-04-2007, 05:43 AM
very nice, but I would like to see a more FPS version...

for the bandwidth problem, you can upload to youtube or some other web brodcast if you don't mind...

thanks for sharing

FelixCat
03-04-2007, 04:05 PM
Beautiful, i can understand the interest of your friend for an HDTV rendering. I think must be very interesting to see it in large size. I canīt imagine how you get those gas jets with the smokers, they really looks as particles with all the subtile details and twists of the gas. Great work.

FelixCat

interstellar
03-05-2007, 11:54 AM
Hi Loon and Felix,

Thank you for your nice comments on my project. Loon, I'll try to get a video up somewhere for you. I'm not sure I want to register with YouTube; it looks too crazy there for me. A few years ago, I registered with another edgy site and I cannot get off their mailing list.

Felix, in order to achieve all the different textures in the gas jets, I just used various settings on the glow lights and Smokers. If anyone would like to see them I could email a copy of my project. I'd have to substitute an uber-sphere for my asteroid, though. My asteroid is about 13 Megabytes in size and I still use an old-fashioned, dial-up internet connection!

Joe T

FelixCat
03-05-2007, 02:44 PM
Hi, Joe. Very kind of you for offering your project for study. I could be very happy if you can (when you have some time) send me a copy of the project. BTW would be a good idea to have some kind of projects repository in the Ei web site...
FelixCat

halfworld
03-05-2007, 03:00 PM
BTW would be a good idea to have some kind of projects repository in the Ei web site...
FelixCat

Lets make our own... After all, the new EI site has a WIKI :)

Great work Joe, I really hope you find a way to get a full speed version online ;)

Again, damn fine stuff,
Ian

interstellar
03-06-2007, 09:20 AM
Hi Felix,

My project contains almost two dozen lights and has a file size of about 2.8 megabytes. If you'll send me your email address (contact me at INTERSTELL@aol.com) I'd be happy to send you the project. I'll have to substitute an EIAS rock or an uber-sphere for the nucleus I used; my ZBrush nucleus is about 12 megabytes (it has a lot of craters) and I can't put that through my email service.

Hey Ian,

Thanks again for your damn fine comment on my project!

Best Regards,

Joe

interstellar
03-08-2007, 10:26 PM
Hi Loon,

I put a compressed, 15 fps QuickTime clip of my outgassing comet nucleus in place of the animated GIF. Please follow the link in my earlier message and it should load up for you (I hope).

Joe T

tumbling nucleus (http://members.aol.com/astroscans/comet.mov)

halfworld
03-08-2007, 10:47 PM
What more can I say, it's every bit as good as I expected it to be! :D

Congrats, I really hope it ends up in your friends show!
Ian

FelixCat
03-08-2007, 10:57 PM
Veeeery nice done, Joe. All the little details sells perfectly the shoot.
Great work.

FelixCat

interstellar
03-09-2007, 09:26 AM
Hi Ian,

Thank you very much for your nice comment. I couldn't have done it without all the tips you and other contributors to these forums have made.

Sincerely,

Joe T

interstellar
06-29-2007, 01:33 PM
Hi All,

I thought I'd update you on my comet project, especially since you guys (William and Richard) helped me along the way.

After I finished setting up the project I rendered it at 1920x1080, 60 frames per second. That way I could be ready for just about anything. It's a good thing I had it "on the shelf"; I received a request for the footage on very short notice. It's being worked into a History Channel show about comets.

Thanks again!

Joe Tucciarone

richardjoly
06-30-2007, 01:08 AM
Thank you for the feedback Joe. This is great news, I'm gonna watch for that show...!
This is a large render, would you care to post render time and hardware if you noted it?
Congratulations!

interstellar
06-30-2007, 10:40 AM
Hi Richard,

I'm on vacation right now and miles from my studio but here's what I remember:

The project contained 18 lights of which about 13 were glow lights shining through Smokers. The nucleus was a ZBrush asteroid; in FACT file format I think it was 45 Megabytes although I forget how many polygons it had. The debris consisted of about 35 Ubershape rocks set to detail level 2. The ZBrush nucleus and every rock were set to cast shadows. I used "Raytrace" Camera but since the motion of the debris was so slow I didn't use any motion blur and it looks fine.

I still use EIAS version 6.5.2. I was in no hurry at the time so I didn't kick on my renderfarm; I rendered the 25 second project on a dual Mac G5 (1.8 Gig). With both processors rendering it took 3 and a half days to make the 1920x1080, 60 fps animation.

Joe Tucciarone

richardjoly
07-02-2007, 02:55 PM
Thank you, have a nice vacation.

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