Hair rendering compositiing solutions

[francescaluce]

i set rendering optimization to large flushable with the scanline turned offmm. you should render your hairs with the rasterizer turned on.
and the raytracer turned off. using detailed shadow maps. you can handle
really a big amount of hairs in this manner and it will be terrible fast.
also about the 'flushable'.. take care that hairs only in rasterizer mode
will get flushed when necessary. if you're not used with the mr rasterizer
mode or the scene has a different setup, only render out the hair and recomp
them in post. take care that you need the 5.1 to get the power out from
rasterizer as for 5.xx there's not implemented the shading quality parameter.

ciao
francesca

[kimaldis]

you should also mess with the *hair* bsp settings. They get pretty critical when the hair gets complex or dense. Method for optimising pretty much as scientific as render bsp, bugger about with them until you hit fastest render. Last time I did this I got render times down from 45 minutes or crash to around 10 minutes.

Fransesca's right about the rasterizer, it'll speed things up considerably but there have been some changes since 4.2.

Avoid area lights like the plague; I had a 20 fold increase in render times over standard shadows. Detail shadow maps work well, though.

[RenisanceX]

THaNX

For more information about setting environment variables, see the XSI Setup guide.




francescaluce: , only render out the hair and recomp them in post

Yeah i have already settle on this seeing when its time to place him with in scenes its better.But thats where im having problems.... the compositing.

How and what passes do i need to be able to lay the hair down on top of each other and still have it look and not loose/overide other layers completely. I was trying to remember how R&H attack aslan's rendering but the speaking was a while ago and i think im missing some key notes from that night.

My main problems which you seem to know francescaluce: is how to comp the layers of hair on top of each other and still have the parts of the lower layers that are suppose to show through do so. Some of the problems that im running into has lead me to either remember that at the R&H speaking some kind of depth matte was used for the layers of aslan's hair or maybe my brain just placing that thought there dunno


KIM Avoid area lights like the plague;

thanx for the advice. ...

At the current moment im using spots... Ideally i'd like to use hdri lighting ived tried it and i can only render half the creature before xsi crashes

Im not a wiz like you at xsi i have been just following the documentation on optimizing hair for rendering and the bsp settings it has which i think or 50 or larger for large scenes if i can recall right and thats what im using at the moment. Any more indepth tips about the bsp ?

ps kim when will that fine little particle plug you were showing during the td love tour be released or sold with the dvd of the tour ;). Was really looking foward to it

[francescaluce]

Ideally i'd like to use hdri lighting ived tried it and i can only render half the creature before xsi crashes
Leo you can't use these things if you have really great amount of fur and hairs.
I'd make a single pass for the hairs and then composite in post. You can disable
the visibility for anything but your fur. for that pass I'd use rasterizer with detailed
shadow maps. Hdri lighting means FG, that is raytraced. raytracing with fur and
hairs is an hazard. with the rasterizer you'll be close to the levels of 3delight
and prman when rendering fur. not only from 3.4 mray has a special mechanism
to flush fur when it comes too heavy in memory or better it divides your fur in
small chuncks that can be loaded and unloaded in memory one at time to give
you more chance to never touch the extreme. so you should be able to render
the whole fur pass. only for the remaing things in the scene you can adopt hdri
or what you prefer. render fur, man, is a challenge. so I'd spend a bit more time
on the rasterizer trying to get a good diffuse look for my fur by using simple lights
with detailed shadows maps. Also how many hairs do you have ? I just put a
ball in a scene with 1mil hair and with rasterizer and detailed (called volumic in
xsi ) shadows maps I got it to render in a bounch of mins with one gb of ram.

ciao
francesca

[ShadowM8]

Well speak of the devil...
I'm doing some R&D on fur and today I have been working on a pass rendering workflow
So far I have been having hard time getting the same result as my beauty render. I have it split into color, spec and shadow pass. One major difference between beauty and composite is the shadowing and to lesser extent specular.

Any advice on how to approach the setup correctly would be appreciated.

[RenisanceX]

francescaluce thanx again

well its a quadraped I have 6 chunks of hair.
4 covering the main body mass area 2 on the face and neck

The lowest level of hair i had at 90000 with strand multiplier of 5
A higher layer at 60000 with multiplier of 3.6
two other layers at 20000 with " " of 3 and 2

then the other two smaller chunks are both 40,000 with multiplier of 4 and 3

[kimaldis]

There are no hard rules for setting BSP, it varies from scene to scene, object to object.

For optimising hair BSP, open up a small render region over an area of the hair and turn on verbose for the region so you can see the wallclock time for the render of the region.
Now, take the max depth and increase it by 5. If the render time decreases, increase it in steps of 5 until it levels off or begins to increase.

Repeat with max size parameter.

getting this will both decrease the render time considerably, it will also reduce the memory requirement.

To comp your hair without the hair at the back showing through you need to occlude the hair at the back of your character. Do this by rendering the character model with the hair but with a constant black surface. You can do this by putting it in a partition and applying the constant shader to the partition.

The course material for the TD Love tour should have been sent out some time ago. If you haven't recieved it yet I'd get in touch with the guys at Softimage. Probably jennifer. If you don't have details for her, contact me (email not message) and I'll forward her email to you.

K.

[kimaldis]

I meant to add, don't forget that Softimage, both the eductions section and the wiki, are great resources when you stuck on something like this. Check out this excelent page:

http://www.softimage.com/education/learning_resources/tutorials/webTutorials/XSI_3_0/Siggraph03Seminars/vfx/FX_Seminar_Siggraph_2003.pdf

[barbapapa]

Im having the same problem compositing the hair...one question, if you oclude the hair with the model rendered in constant black how do you go about compositign it with the other render. Because the result will give an alpha channel of the model and the hair , but not just the hair that must be seen in the front... Don know if that was clear. the other thing is that you loose the shadows of the hair cast over the model. Any ideas on how setting up this?

[barbapapa]

bump .......

[Pooba]

Im having the same problem compositing the hair...one question, if you oclude the hair with the model rendered in constant black how do you go about compositign it with the other render. Because the result will give an alpha channel of the model and the hair , but not just the hair that must be seen in the front... Don know if that was clear. the other thing is that you loose the shadows of the hair cast over the model. Any ideas on how setting up this?




same question..

[Pooba]

bump..................................

[Zerflag]

Im having the same problem compositing the hair...one question, if you oclude the hair with the model rendered in constant black how do you go about compositign it with the other render. Because the result will give an alpha channel of the model and the hair , but not just the hair that must be seen in the front... Don know if that was clear. the other thing is that you loose the shadows of the hair cast over the model. Any ideas on how setting up this?

the answer is quite simple: set your rgba of your constant shader all to 0 (this way you have black alpha as well)

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.