How do I combine an (animated) 3D scene with a static backdrop picture, so that the "ground object" only receives the shadow from the scenes other objects and do not display any self shadowing? I have tried al kinds of combinations (flatshaded/0% falloff/render only shadow etc) with no luck. Anybody knows how or know of a tut showing the procedure?

...oh yeah...by the way: why doesn't the shadow cast on the ground get tinted by the color of the ground? The shadow should by brown in the rendered image...

I tried sampling it in Photoshop and it is browner than an equivalent grey would be.

Perhaps turn off "Cast Shadows" for that object?

That is not due to the color of the object, but because the (brown) background shines through. The object designated for front projection apperantly turns into a greyscale in the rendering.

Yep, have a look into the Options of the object.

*Fuchur*

Nope...unfortunately that doesn't work. Neither does switching on flatshading - then the self shadowing disappears but so does the cast shadow :-/
But thanks for the answer!

It you to mix the color of the object with a front projection then you may need to literally front project on it. A light can take an image as a gel and a light can be matched to the position of the camera. "Light Lists" can be used to make the light shine only on the desired object.

Well, first of all I want to composite 3d renderings with a backdrop so 3 elements can be seen:

1. the 3d objects
2. the backdrop
3. the shadow from the 3d objects

like eg this: http://vimeo.com/18665952

It shouldn't be that hard, I'm just to stupid to find out how...:-)

The sample pic you show looks right. Why do you want the front projected image to become tinted very dark brown?

It isn't the tint that is the main problem. The real serious thing is that I can't get rid of the 3d-ground (the round plate)'s self shadowing, without at the same time loosing the shadow from the red 3d object.

Regarding tinting of the shadow: as can be seen in the background picture the shadows there are rather brown in tint. It would be nice (if at all getting this to work) to be able to adjust the thrown 3d shadows to blend in with the background.

Z-buffered shadows from Kleig lights can be given a "tint" (black is default). Under Options

Can you post an image to use with that PRJ?

:-)

ToreB,

HELP IS HERE brother!!! A while back, I had to extensively work on this in order to use Hash in my many projects and composites over the years. ....I re-worked your project to get the shadow only..

Click to view attachment
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Hope this helps my friend!

Cheers,

William

Oh yeah.....in the render options panel make sure to check only the "Alpha" and "Shadow" buffers...

THE TRICK to getting rid of the "Self" shadowing on the ground plane is to use a "White" only rotoscope on the camera and the make the ground model both projection and Flat shaded. STUDY THE two MODELS new render settings that I made.

As far as the "brown" color...It can be tinted in just about any post app.

Cheers,

William

Here's a quick test using your image. Let me know if this helps.

Click to view attachment

Cheers,

William

Hi William,

and thanks a lot for your answer, and your work finding a solution! This method really seems to be working :-)

It could be nice and work saving though, if A:M offered a one-click-solution, merging all these post processing / compositing steps into one simpel option within the program.
Maybe a feature to wish for in future versions?

Here's my all-in-A:M version

Click to view attachment


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HOWEVER, i don't think that brown patch over at the side of the picture is a shadow, I think that's overturned dirt because none of the other objects in the picture cast a shadow in that direction or in that color. Everything else has a very hazy "AO" shadow only.


But, you can make a colored shadow in A:M if you need to.

Looks awesome Robert.... How did you count out the shadows on the rim of the ground and the shodows on the space ship?

FANTASTIC! Thanks Robert!! This is exactly what I was looking for. And, yes, how DID you do it? I have trying to find out how you did it...but couldn't see anything different from my original file???
Please enlighten! :-)

And you're absolutely right: the darker stuff in the left is dirt in another color and not shadows. But never mind the color tinting was just a secondary issue. My absolutely main wish was to be able to make the seamless composite. This will save me lots and lots of rendering time! So thanks again, and please tell how you did it!
:-)

Getting rid of the shadow on the edge of the disk was just a matter of backing the light farther away so it lit the entire disk.

There is a slight edge where the disk meets the background color. It would be easy to shape your ground plane so that happened where there was some obvious edge in the background image like at the foot of the building.


I hadn't noticed that the red glob wasn't self shadowing but I'm not sure why it isn't. that may be a bug.

It has something to do with using a z-buffered light instead of a raytraced one, but it should be self shadowing in my PRJ. Hmmmm.

Yes I see how you did it now. Not as perfect as I thought first. The need for adjusting the light so the groundplane don't show up, dictates the lighting for the rest of the scene in an unacceptable way.

I would like to be able to set up a complete scene with both sets, props and actors, then render this WITHOUT the animated parts (the actors, typically) in a very high resolution (2 or 4K), then load this rendering as a rotoscope/backdrop, and turn on the actors (and their shadows) on top of that.
This procedure would cut render times dramaticaly, as only the animated elements would need rendering on a per frame basis.

But if the lighting setup has to change between backdrop rendering and animation rendering, it would cause inconsitencies not acceptable - for me anyhow.

Well, back to the wishfull thinking then...

Why do want to not completely illuminate the ground plane?

Because that would affect all the other elements in the scene - which I do not nescesarily want to be illuminated that way.
Take eg a scene like this from Trapez. Try to imagine what difficulties it would entail to seperate the character (and his shadow) from all of the rest of the scene...

William's (Detbear) method will still work for you I believe.

And I'm sure there's an all-A:M solution also. Just need to think about the tools a bit more.

Williams method works, but isn't very straightforward.

An all-A-M solution would certainly be sweet!

So the object is to reduce render time, right?

How long is it taking to render that now?

The problem is that your lighting does not even come close to matching the lighting in the background image.
The lighting in your chor is for a very dark stage with a bright spot light. The lighting in the background image is outside in full sunlight. Unless you change your lighting, it will look unnatural. But if you don't mind if it looks unnatural, you would have to approach the problem like this. See the attached project file.

this great stuff. I am thinking of rendering as it were in layers

Sorry, Homeslice, but that's simply not true.

In the attached 4 pictures I have tested a scene with exactly the same lights on foreground and background, and you can clearly see that the groundplane excibits self-shadowing and contributes to the composited rendering in anvery unfortunate way. The edge of the circular scene is very visible and what looks like double exposing is the kliegs sweet spot is apparent.

Every major 3d pacakage I know has this simple feature - to turn an object off, so it becomes completely transparent - EXCEPT for shadows cast on it. And I took for granted that A:M could do this too, and that it was just me fumbling and couldn't get it working.
Thats why I asked here in the forum. Apparently there is no such feature in A:M. So I guess I'll just request it in the A:M Mantis.

Thanks a lot for trying to help me out though :-)

What's wrong with this one, again? Until i told you HOW I did it, it looked just right, no? It was what you said you were trying to get.

Suppose we could get this but without the volumetric beam of light...

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And use that as a background image for aniamtion like this but just the man and the beam of light...

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And together they got you this...


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Would that do it?

Well...what about the shadow cast by the actor on the ground (stage floor)?

And why not have the volumetrics (which by the way is on all of the scenes 10 or so kliegs) rendered once and for all on the rotoscope/background? One of the reasons for doing this is to move tgings that takes long time to render - as volumetrics and mist and the likes - into the backdrop for time savings sake.

I still think it would the easiest and most straight forward thing to have the option as I have described.

The example I have given here is just one scene. Other scenes could have completely different lighting setups and it would be to much hokus pokus to make new lighting strategies for every new scene, in my opinion.

The easy thing is a switch turningg of a given object, except for the shadows (not the light) cast on it.

The volumetric light never has to move?

Is this problem the one thing stopping you from getting this movie done?

No, the condition for this "trick" would be stationary camera and stationary lights (unless some kind of tracking software were used - I think the Soulcage guys once made a succesfull tracking compositing shot with A:M)

Well not exactly stopping me...but it certainly would be a nice way to cut down on render times...
A:M isn't exactly a Ferrari when it comes to rendering of volumetrics / particles / and the likes - but it has such a beatifull and painterly way to render light :-)

These images are different than the one you included in your sample project. OF COURSE THE LIGHTING IS DIFFERENT in the *other* images of the stage. Those are not the ones I tested with and they are not the ones I was talking about., You didn't even look at my project file or you would have seen how to get the effect you want. I'm beginning to think you don't even want a solution.

OK, then. Don't panic yet. I think there's solution, we just have to let it simmer a bit. Put this problem on hold and work on some other part inthe mean time.


How long does it take to render this, but without the volumetric light?

Click to view attachment

It ticks in at exactly 6:17.

...and is very very dark!

the only reason n00b is about to do the fab gab flab is, i was studying this a while back and
i tried pushing all the buttons too, to no avail, and the solution was:
the "shadow only" option is not visible in any image - it is stored in the alpha channel of that image.
i never worked further, accepting the abstract as an answer and the tut is here:
http://www.hash.com/forums/index.php?showt...l=alpha++buffer

I think that this is a method that can achieve the results you want within AM and without using external compositing. It is a somewhat 'old' trick that many software packages used before. I have not tried it using a volumetric light but from what I understand, you will pre-render that anyway.

Click to view attachment

This is a folder with some html files explaining the process. I hope it is clear, since I wrote this a few years ago. I hope this can help you.

Javier

Basically, you're going to use that as the front projection image and project it back onto the whole geometry of the set (not just a flat plane) then set up the character and the volumetric spot light on top of that and render the animation.

Before you say it can't work, I'll say i know it will if you do it right.

Apparently I have offended you some way - that was certainly not my intention. I'm very gratefull for the help you offered. But I am not looking for a solution for a specific setup or a tweek, but for a feature that is general, and can be used in every ligthing situation. As it would be if A:M had a simple "shadows only" switch.

I have now put this request up:

http://www2.hash.com/reports/view.php?id=5848

So lets see if something comes out of this in future A:M versions :-)

Here's the scheme:

Your situation is like this, a set with complex lighting and textures and an animated character in a spotlight:

Click to view attachment 38 seconds to render



You turn off the character and Spotlight and render this:

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Then you delete all the materials from the set and turn everything up to 100% Ambiance. it will look like this:

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Set all those objects to "Front Projection Target" ON and use the above Background only render as the Camera Rotoscope. Turn on the Character and spot light:

Click to view attachment 4 seconds to render




Problem solved!

He he! How inventive you are!

But if you have to be nitty-gritty (and you know I am), the two pics - before and after - are by far identical:

Click to view attachment

There's a loss of contrast in some areas and not in others, and it seems like the fill light's shadow disappear alltogether (but maybe that is due to the weak contrast/gamma).

I myself was beginning to experiment a bit with A:M's composit options - you know, using the clean shadow buffer as a third layer in a foreground/background composit - but ran into all sorts of really strange behavior, and had to give up. It all get's unnescesary technical, and the time spend on experimenting plus setting up some elaborate pipeline for each of the shots, comes to outweigh the time saving gained by the shorter render time.

I think I need to go back to animating now. And of course keep my fingers crossed that something come of my feature request!! ...one little switch to bring the shadow buffer into the render/chor that's all!!

Thanks a lot, Robert, for all your great input and everybody else too for all the helpfullnes!

I believe you wouldn't have to do that. Just set all the models (other than the knight character) to front projected ON (but NOT flat shaded), ground plane is front projected and flat shaded (probably, depending on shadow types). The front projection will override materials, decals (except for hair, particles)

gets this

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