One of the trick to accelerate the calculation on animated character is to
bake first your light diffuse contribution ( Area, spot light, point light )
in an environment map and convolute it. And use it like any environment
lookup plugged in the ambient slot of your SSS shader ( or any others shader
actually ). This 2 pass approach will give you any type of lighting for
almost for free. You will still have to use your light to calculate shadows
and specular of course but theses calculation are less heavy than diffuse
and indirect.
To accelerate any glossy reflection involved in your shader I strongly
suggest to use Arch-mat shader and add it to the SSS shader.
Have a look to MasterZap blog for that.
Harry Bardak
TD / Compositor.
Http://www.harrybardak.co.uk/
+44 781 661 4147
----------------------------------------
> From: peter_b(at)skynet.be
> To: XSI(at)Softimage.COM
> Subject: Re: rendermap / lightmap SSS shader
> Date: Wed, 28 May 2008 11:03:52 +0200
>
> You can bake illumination with regular rendermap too - looks much better
> to
> me - with the bump and geometric detail and displacement. You're loosing
> most of that with vertexmap.
> And with the density of meshes I had it was crashing all the time.
> For a human face I'm down to 3-4 maps as is - and the comped results are
> fine. For full body it can be 8 or so and for quadrupeds 10 and upwards.
> With a lightmap working in UVspace this would be one single rendermap -
> doenst seem all that far fetched to me.
>
>
>
> ----- Original Message -----
> From: "Andreas Bystrom"
> To:
> Sent: Tuesday, May 27, 2008 11:09 PM
> Subject: Re: rendermap / lightmap SSS shader
>
>
> you can also try baking the illumination into a vertexmap, and then
> "comp" the textures on top of that.
>
> if you need lots of detail you can subdivide the mesh a bit. I found
> this method to be working rather well, I still had to rendermap from
> 3-4 different camea-locations but it was much easier to get nice
> smooth results compared to rendermapping into textures.
>
>
> On Tue, May 27, 2008 at 9:07 PM, peter boeykens wrote:
>> Thanks for the link.
>>
>> I am doing multiple rendermaps with the camera in different positions,
>> and
>> recombining them - this gives me a fairly good result.
>>
>> It's just a lot of work - mostly because of the very slow rendering times
>> and instability of rendermap.
>> A 2k rendermap is 1.5 hours on average on the stuff I'm working on -
>> regular
>> 2k renders are less than 15 minutes. I'm scripting overnight renders of
>> several rendermaps which helps out a lot - but one night out of two
>> rendermap either crashes, freezes or simply disappears.
>>
>> ...
>>
>>
>> ----- Original Message ----- From: "Halfdan Ingvarsson"
>>
>> To:
>> Sent: Tuesday, May 27, 2008 5:06 PM
>> Subject: RE: rendermap / lightmap SSS shader
>>
>>
>> It's not complicated what it does. It's basically a trick they used on
>> Finding Nemo, described in some Siggraph notes, but using the camera's
>> pov,
>> rather than the light's pov. (see:
>> http://graphics.stanford.edu/facecourse/facecloning05/Presentations/scat.pdf
>> )
>>
>> The lightmap contains the interleaved illumination of the front and back
>> surfaces (+depth of back) as seen from the camera, then the fast_sss
>> shader
>> simply blurs the image samples based on distance, for each sample lookup.
>> This is why this trick won't work in a wraparound mode. If you froze the
>> lightmap and then orbited, the SSS effect would look quite funky where
>> you
>> were viewing perpendicular to what the original camera's sampling
>> position
>> was.
>>
>> The only decent way to do it would be something along the lines of what
>> Alan
>> describes.
>>
>> - ½
>>
>> -----Original Message-----
>> From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf
>> Of
>> Alan Jones
>> Sent: 27-May-2008 10:55
>> To: XSI(at)Softimage.COM
>> Subject: Re: rendermap / lightmap SSS shader
>>
>> On Tue, May 27, 2008 at 3:20 PM, peter boeykens wrote:
>>>
>>> For "unsupporting" SSS - this seems lame - as it wouldn't take all
>>> that much to get it to work.
>>> The downfall is with the lightmap being camera dependent.
>>> I dont think that's a limitation of lightmaps - as color sampler
>>> lightmap is working with UV space.
>>
>> The fast SSS shaders don't do anything akin to an ordinary lightmap in UV
>> space.
>> They use lots of strange trickery behind the scenes to do their work and
>> Zap
>> is very tight lipped on their secret sauce used. Don't forget that Halfy
>> is
>> an exceptionally intelligent guy, if there was something on his end he
>> could
>> do to resolve this it would already be done.
>>
>> There's nothing stopping you from writing/employing someone to write your
>> own SSS shader which could achieve similar speed using lightmaps by doing
>> some nice trickery to store to a kdtree/bih instead of a UV space texutre
>> and then looking that up within the main shader. It'd be nice and fast
>> and
>> you'd avoid the camera dependency that makes fast SSS so unhappy.
>>
>> Though if you use SSS a lot grab a copy of 3Delight - their SSS is
>> absolutely gorgeous, though I've not look at whether they support
>> rendermapping in XSI, though I'm sure Aghiles would be more than happy to
>> provide customers with something that does this within XSI in order to
>> get
>> 3Delight into a new facility.
>>
>> Cheers,
>>
>> Alan.
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