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View Full Version : Multipass rendering a sequence: is it possible in LW?


lmancg
08-09-2005, 12:02 AM
Hi all,

I've briefly done this at school a couple years ago so I need a refresher course. Here's the question:

How can I set up LW so that it would render a sequence with specularity, diffuse, reflection, transparency, shadows, etc. in different passes?

I've done this long time ago with a still image and was wondering if this is possible with a sequence. The purpose of this is so I can edit these passes individually in a compositing program (specifically After Effects). Any suggestions will help jog my memory. Thanks!

Varinder
08-09-2005, 12:10 AM
I'm also trying to figure out the same thing in lightwave. I've been trying to do it all day today and yesterday, but cant seem to figure it out in lightwave. I've done it in 3ds max, but its wierd in Lightwave. I'm also using HDR images to light my sequence, is there anything special i need to do when rendering with HDR lighting in passes?

thanks in advance!

KillMe
08-09-2005, 12:29 AM
get teh surpasses plugin and all your passes are pretty much set up for ya

m.d.
08-09-2005, 12:40 AM
image processing.....PSD export....all sorts of buffers built right into lightwave,transparency,diffuse,specular and a bunch more 1 pass and it's done.

And if you have DFX+ or DF4 it has an import function that merges the layers into there proper merges and modes(there is a problem with one of the passes merge modes though)

Varinder
08-09-2005, 12:49 AM
people always refer to digital fusion for compositing with your renders, but what about combustion or after effects? Can it be used the same way or is it just easier in digital fusion?

Caine607
08-09-2005, 12:57 AM
Image Processing/Render Buffer Export.

m.d.
08-09-2005, 01:03 AM
i'm not sure on combustion's PSD import, probably has some form.

i love fusion, i was trained on combustion, but i will always use fusion if i have the choice...more intuative in my humble opinion.Shake is also a kick ass compositer (if you got a Mac)

that being said all of them will do mostly the same thing with various strengths and weakness.

i would assume AE has a good PSD import.

m.d.
08-09-2005, 01:09 AM
i havn't tried the render buffer export, i think it only output's 1 buffer of your choice though, whereas PSD export is up to 22 or so.

note these can create huge file sizes,like 12 megs per frame or more so only use the buffers you need.

Varinder
08-09-2005, 02:01 AM
I seem to have a problem with when i render my passes out. I've used lightwave's render buffer, PSD export and buffer_saver. And my results are always the same, where the shadow pass is always just black. Can someone maybe explain why this is happening? Is there some setting i need to put on to see the shadow pass properly?

gerardo
08-09-2005, 06:39 AM
Varinder, are you sure you have a shadow and not a shading provided by GI (occlusion effect)?
M.D., we can add Buffer_Export in multiple slots :)
ASA_Buffer_Saver is very useful too



Gerardo

Varinder
08-09-2005, 07:27 AM
Yah, im using the Gi shading, i had a feeling that that was the reason i couldnt see the shadow. So how else would i be able to get a shadow from an HDR lighting setup? I'm just doing a bunch of tests right now with live action shots integrated with 3D characters. I cant seem to create a seperate shadow pass to put under the character.

I tried this tutorial out, http://www.andrew-whitehurst.net/hdri_tut.html, but when i get to the part where u create the 'difference matte', when i do that in photoshop, my character in the scene gets inverted, like all his colors and what not get inverted and i dont know how to get it back to normal.

Any help with this would be awesome, thanks.

lmancg
08-09-2005, 06:20 PM
i havn't tried the render buffer export, i think it only output's 1 buffer of your choice though, whereas PSD export is up to 22 or so.

note these can create huge file sizes,like 12 megs per frame or more so only use the buffers you need.

I have most recently attempted the PSD-Export. I've imported all the layers individually in After Effects but I'm not sure how the layers should be read. Do they have to be 32-bit PSDs when bringing into After Effects? Do I have to apply specific blending modes to the layers? Do I have to key anything?

Also, is it economical to use PSD-Export for sequences? The PSDs I exported out of LW were roughly 30Mb each. Is it more economical to just have separate scene files for the same sequence rendering out the different passes?

I'm going to try the Render Buffer Export next.

gerardo
08-10-2005, 10:00 AM
Yah, im using the Gi shading, i had a feeling that that was the reason i couldnt see the shadow. So how else would i be able to get a shadow from an HDR lighting setup? I'm just doing a bunch of tests right now with live action shots integrated with 3D characters. I cant seem to create a seperate shadow pass to put under the character.


Only lights generates shadows. Shades provided by GI aren't interpreted as shadows; so if we want to make a shadow pass, we need to add a light with shadow enabled (shadowmap or raytrace); then you will be able to generate a shadow pass with PSD_Export, Buffer_Export, ASA_Buffer_Saver or simply setting the surface alpha_channel according to shadow_density (SurfaceEditor / Advanced).
Btw, G2 includes a special tool to solve this very easily: LSD (Luminous Shadow Darkening); very cool feature!


I tried this tutorial out, http://www.andrew-whitehurst.net/hdri_tut.html, but when i get to the part where u create the 'difference matte', when i do that in photoshop, my character in the scene gets inverted, like all his colors and what not get inverted and i dont know how to get it back to normal.

Any help with this would be awesome, thanks.


There are several ways to make this (there are even special matte tools for this task); however a simple way that works for all packages (you can even avoid PS and to do it in LW), is to make a render (GI) of your character and the local scene, (let's say a plane surface to do it simple), matched with the background image; let's call to this img1. Then render just the local scene (without cg elements) with your HDRI; let's call this img2. Also is very important to have a mask or alpha channel of the cg elements (img1_alpha) and the local scene (img2_alpha). Then the composition would be in 2 parts:
In the first part, set as base img1, this image should be modified by the mixture of img1_alpha and img2_alpha, so that we only see the local scene. Above this, set img2 in difference mode; img2 should be modified by img1_alpha, so that we only see the local scene and not the areas where the cg elements are. You can make a nesting, precompose or render of this part (let's call it pre_comp). What you should obtain in pre_comp is the difference between img1 and img2 where is only shown the local scene, without background and cg elements.
In the second part of the composition, set the background as base; above it, set pre_comp in difference_mode; above both, set img1 modified by img1_alpha, so that we obtain the CG elements above the final result with the differential rendering.
Btw, in LW we can do this in a very simple way too (without compositing) using front_projection on the local scene :)



Gerardo

jeremyhardin
08-10-2005, 10:50 AM
there is a problem with one of the passes merge modes though
this was fixed in one of the 8.x updates.

digital verve
08-10-2005, 11:07 AM
Make sure that you are using LW 8.3 as Newtek corrected and enhanced the psd export to work and be useful. If you haven't updated yet then 8.5 should be out by next week (my guess).

Varinder
08-10-2005, 10:26 PM
Hey gerardo, thanks for your help, helped out a lot.

I wasnt able to do what you asked to do in photoshop since my photoshop skills arent that great. I was able to render everything and in alpha. But i wasnt sure how to modify my rendered image with the alpha channel in PS. If you think you can help me out with that, that'd be awesome. And also, if you dont mind, can you explain how to do that 'front-projection' thing in LW, if thats easier then going into PS and doing all that stuff, then i'd rather do that :)

Thanks in advance.

-Varinder

Varinder
08-11-2005, 06:44 AM
Alright, i learned how to do front projection and its quite a neat trick and easy to do. But i cant get it to work the way i want it still. Like, i got the ground (what the character is standing on) to project the image in the background, but not completely, you can still see it a little. I cant figure out how to completely get rid of the ground floor and keep the shadow of the character on the plane. I think the reason why the ground isnt completely disappearing is because its still getting 'light information' from the HDR image thats lighting the scene from Image World. So, im trying to figure out how to tell LW not to put any light on the ground but still recieve shadows from the character. If anyone knows how to do that, that'd be awesome, thanks!

m.d.
08-11-2005, 07:07 AM
Also, is it economical to use PSD-Export for sequences? The PSDs I exported out of LW were roughly 30Mb each. Is it more economical to just have separate scene files for the same sequence rendering out the different passes?
PSD files are big, and the trade off is you can usually do it with one pass.And a lot of those buffers you will likely not use and can turn them off.

The one I actually use the most is RPF, which will output most of what I need....and sometimes the Zbuffer from PSD has been really buggy for me. It's file size is considerably smaller than PSD,and you can always run a separate PSD export for reflection,ect if you need it.

gerardo
08-11-2005, 08:01 AM
Hey gerardo, thanks for your help, helped out a lot.

I wasnt able to do what you asked to do in photoshop since my photoshop skills arent that great. I was able to render everything and in alpha. But i wasnt sure how to modify my rendered image with the alpha channel in PS. If you think you can help me out with that, that'd be awesome. And also, if you dont mind, can you explain how to do that 'front-projection' thing in LW, if thats easier then going into PS and doing all that stuff, then i'd rather do that :)

Thanks in advance.

-Varinder


Ok. I've made a little tutorial about this compositing process. To show how simple it is, I use LW Textured Filter (Effects/Processing/Add_Image_Filter); I think this tool (TF) is more powerful than LW compositing panel :) but the same process can be used in any other composition software:

http://www.geocities.com/cgtalklinks/phase1.txt

http://www.geocities.com/cgtalklinks/phase2.txt

http://www.geocities.com/cgtalklinks/phase3.txt

(In final image, local scene is grainy because for an explanatory purpose, I've just rendered without antialiasing)



Gerardo

gerardo
08-11-2005, 08:24 AM
Alright, i learned how to do front projection and its quite a neat trick and easy to do. But i cant get it to work the way i want it still. Like, i got the ground (what the character is standing on) to project the image in the background, but not completely, you can still see it a little. I cant figure out how to completely get rid of the ground floor and keep the shadow of the character on the plane. I think the reason why the ground isnt completely disappearing is because its still getting 'light information' from the HDR image thats lighting the scene from Image World. So, im trying to figure out how to tell LW not to put any light on the ground but still recieve shadows from the character. If anyone knows how to do that, that'd be awesome, thanks!

If you are talking about shadow (cast by a light), let's say intensity at 100%; you can do this:
Set diffuse about 50% (your table surface), and luminosity 50%; play with these parameters until you match perfectly with your background plate, don't worry about the shadows here,
Then set up this simple light rig:

Supposing you are using luminosity about 50%:
Light1: 100% Affect_Diffuse/shadows OFF (if you don't want the light affect your objects diffuse, you can avoid this light)
Light2: 200% Affect_Diffuse/shadows ON
Light3: -200% Affect Diffuse/shadows OFF
This way you can control your shadows strengh without affecting the diffuse of your surfaces
like I said previously, G2 has a very nice tool (LSD) for this specific task :)



Gerardo

EDIT: If you are talking about shades (provided by your GI solution) maybe you want to make a mask (a gradient, weightmap or bitmap) in transparency channel, to blend your table with the background

Varinder
08-11-2005, 08:36 AM
First off WOW, Gerardo you are the best, man. I really appreciate you taking the time and making a kick ass tutorial like that, thats really amazing. Ima try out your tutorial right now and let you know if it worked out. Thanks again man, really appreciate it.

gerardo
08-11-2005, 08:41 AM
First off WOW, Gerardo you are the best, man. I really appreciate you taking the time and making a kick ass tutorial like that, thats really amazing. Ima try out your tutorial right now and let you know if it worked out. Thanks again man, really appreciate it.

You're welcome. Hope it helps you :)



Gerardo

Varinder
08-11-2005, 12:09 PM
Hey Gerardo, in your 'phase2'.jpg, i did all that stuff in TF but i have no clue how you rendered those out and got those pictures on the right with the difference applied, the precomp. Again, I'm not very good at compositing tricks yet, still learning, so do you mind explaining how you did that? Like once you put all your files into the texture filter...how do i render those images the way i want it or the way you did it?

gerardo
08-12-2005, 12:38 AM
Sure. You don't need to render out those pictures :) they just are a graphic representation about what is happening with that group of layers.
The idea is to render a picture with the cg element and local scene in where the alpha shows your cg element but not the local scene (you need to set constant black for your local scene's alpha) and use a format that supports alpha channel (or render it as an independent sequence)
the other picture is the local scene only (without cg element or dissolve 100%) and its normal apha.
In Image editor you need to set your images this way:
for img1 (cg element + local scene): enabled alpha; for this image make 2 clones:
first clone img1: disabled alpha
second clone img1: alpha only
for img2 (local scene only): enabled alpha, for this images make 1 clone:
clone img2: alpha only
Then you may set these images as layers in Textured Filter :)



Gerardo

Varinder
08-14-2005, 04:19 AM
Alright Gerardo, need your help again buddy. Ive been trying to do your tutorial and for the longest time for some stupid reason i wasnt able to get the results you were getting. But finally today i got the 'difference in local scene (precomp)' rendered just the way you have it. But, once i got that figured out, in 'phase3.jpg' i did exactly what you showed in your tutorial, but im not getting the shadows in my scene still. My character is just standing there with no shadow underneath him still. I have the exact same settings as you do in that tutorial of yours, but im not getting the same results as you. I have a feeling it has something to do with my difference in local scene (precomp) render, but I'm not sure what to do to make it work. So, wondering if you could help me out with this once more :D I have no clue why such a simple thing of getting a shadow under your character is so hard to figure out for me, lol. I've done it before in max but in lightwave its been a pain in the ass. Anyways, hope to hear from you soon. Later

-Varinder

gerardo
08-14-2005, 08:31 AM
mmm... I guess your cg element doesn't have the alpha channel set appropiately, but is hard to say what happen without seeing your layers. Can you post some pictures (low res) of your background, difference in local scene and cg element + alpha to take it a look?



Gerardo

Varinder
08-14-2005, 09:29 AM
Sure no problem, i'll send it through yousendit.com, make it easier. I put in a bunch of images you can look at. This is also just a test to see how to get hdri shadows, so it's really sloppy lol.

http://s26.yousendit.com/d.aspx?id=0EJG450K5U8XF3LQLH374KGSUH (http://s26.yousendit.com/d.aspx?id=0EJG450K5U8XF3LQLH374KGSUH)

gerardo
08-14-2005, 01:19 PM
Sure no problem, i'll send it through yousendit.com, make it easier. I put in a bunch of images you can look at. This is also just a test to see how to get hdri shadows, so it's really sloppy lol.

http://s26.yousendit.com/d.aspx?id=0EJG450K5U8XF3LQLH374KGSUH (http://s26.yousendit.com/d.aspx?id=0EJG450K5U8XF3LQLH374KGSUH)


You are doing this very well, Varinder. Congratulations! btw, the solution was pretty simple:

http://www.geocities.com/cgtalklinks/problemsolved.txt

Your layer of difference in local scene is right, just disable its alpha channel :)

I think a real problem is your local scene is inconsistent with the background plate, since your local_scene's diffuse reflactance is too high, they don't MATCH. Is hard to say if problem is color or diffuse, but I guess the problem is the color (is too bright). A nice tip to find out the proper color, is load your background plate in PS or any 2D software, select an area of the local scene where lighting is measured and apply it a lot of Gaussian Blur; commonly what remains is one flat color; pick this color and take note of its RGB values; then copy these values in your local_scene surface (table). Render. Compare and adjust luminosity or saturation (from Color Panel) if is necessary. Render again until you match the flat color you have in color channel (this process assumes you have the appropriate gamma and exposure for your light-based model)
Once you've matched your cg element and local scene with the background image you may obtain a better results :)
I tried to find a HDRI that matched the most possible with your background. I used 100% in diffuse channel with this color: R:203 G:182 B:146

background
http://www.geocities.com/cgtalklinks/Bckgnd.txt

local scene (note the diffuse level)
http://www.geocities.com/cgtalklinks/Ls.txt

local scene + cg element
http://www.geocities.com/cgtalklinks/Lscge.txt

difference in local scene
http://www.geocities.com/cgtalklinks/Dils.txt

final result
http://www.geocities.com/cgtalklinks/Result.txt

I'm sure you will achieve a better result with your distant scene :)



Gerardo

Varinder
08-15-2005, 12:30 AM
Thanks Gerardo that cleared it up nicely. Now i finally know how to put shadows under my character through HDRI lighting, thanks to you, i really appreciate it. :)

But, like always you fix one problem, another rises. Once i figured out how to put shadows under my character, i decided to render the same scene with AA (Antialiasing). I did everything the same way i did before, but when i tried to render out my precomp, you see a border of the local scene for some reason. It has something to do with the AA rendering, because when i render it without AA , the border line is gone. I tried a bunch of different settings, but couldnt get the border to dissappear. I'll post up the pick incase your wondering what it looks like:

gerardo
08-15-2005, 11:22 AM
Thanks Gerardo that cleared it up nicely. Now i finally know how to put shadows under my character through HDRI lighting, thanks to you, i really appreciate it. :)


:thumbsup:



But, like always you fix one problem, another rises. Once i figured out how to put shadows under my character, i decided to render the same scene with AA (Antialiasing). I did everything the same way i did before, but when i tried to render out my precomp, you see a border of the local scene for some reason. It has something to do with the AA rendering, because when i render it without AA , the border line is gone. I tried a bunch of different settings, but couldnt get the border to dissappear. I'll post up the pick incase your wondering what it looks like:


Ok. I understand, none others problems rises; what happens is for the purposes of the previous tutorial (show the logic behind the process), I didn't take into account the antialiasing :)
Basically when we need to do this, we use composition softwares that have tools and special options to manage alpha channels and mattes, and commonly this can be solved with only 3 or 4 layers.
I suppose in LW we have this situation because apparently LW interprets the alpha channel as Premultiplied (matted with black color) and also, since we are using TF, pixel_blending option "increases" the situation. In a composition software we would solve this changing alpha channels to Straight (unmatted).
As I said previously, is better to do this in a composition software, but if you want to make everything in LW, I find you have at least 2 options:


A. Render everything at quadruple resolution without antialiasing. This supposes to use a considerable number of RaysperEvaluation and to add the motion blur effect in post (what implies to lose the opportunity to use some cool tricks with this feature). Isn't my first option but it can be viable in some cases :)


B. You can change slightly, the process described previously and make this:

http://www.geocities.com/cgtalklinks/comp1.txt

http://www.geocities.com/cgtalklinks/comp2.txt



Gerardo

Varinder
08-17-2005, 07:10 AM
Alright, Gerardo you genius, that helped out a lot. The shadows look a lot better now, without the stupid borders. I think im done with learning how to composite in LW now. :) So, again I really appreciate your help man, helped out a lot thanks buddy.

gerardo
08-18-2005, 09:55 AM
hehe... glad it helps you :) and yes, those annoying edges aren't so easy of remove; for that reason I think that it's easier to make it in a composition software. If you only have PS to do this, you can do it there too (at least with one image), although certainly Photoshop would not be my first choice for this kind of task (since isn't a software designed for composition of sequences).
I suppose there are many ways of making it in PS, at least is easy with a single picture:

http://www.geocities.com/cgtalklinks/PScomp.txt

but I consider difficult to do the same thing with a sequence (maybe somebody more skillful with PS can advise you some other better technique).

If you are planning to do this with a sequence and you only have PS and LW, at least for me, is advisable to make it in LW. If you have some composition software, the process is even more simpler than in LW and PS. Here you can see the process with AE, but the principle is the same for any other CS:

http://www.geocities.com/cgtalklinks/AEcomp.txt

btw, good luck with your project! :thumbsup:



Gerardo

Varinder
08-19-2005, 06:20 AM
Hey Gerardo, those 2 .gif tutorials you made worked out amazingly. I was able to composite my scenes so quickly and smoothly in both those programs, PS and AE. Thanks a lot man. Thats really all i needed to know right now. I've been doing a bunch of really simple tests with your tutorials. Now im gonna make some really cool stuff :)

Thanks again buddy, you are #1 lol.

gerardo
08-20-2005, 04:10 AM
Hey Gerardo, those 2 .gif tutorials you made worked out amazingly. I was able to composite my scenes so quickly and smoothly in both those programs, PS and AE. Thanks a lot man. Thats really all i needed to know right now. I've been doing a bunch of really simple tests with your tutorials. Now im gonna make some really cool stuff :)



:thumbsup:



Gerardo

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