Re: [Algorithms] Normal map blending for creases in geometry

[Alex W. <Ale...@im...>]

=0D=0A=09-----Original Message-----=0D=0A=09From: gdalgorithms-list-bounces=
@lists.sourceforge.net=0D=0A[mailto:gda...@li...urcef=
orge.net] On Behalf Of=0D=0ADaniel Yeung=0D=0A=09Sent: 07 July 2006 15:51=0D=
=0A=09To: Game Development Algorithms=0D=0A=09Subject: Re: [Algorithms] Nor=
mal map blending for creases in=0D=0Ageometry=0D=0A=0D=0A=09Firstly, sorry =
if I made myself unclear... linear interpolation=0D=0Abetween=0D=0A=092 nor=
mal maps is what I will be doing, the question was actually=0D=0Aabout meth=
ods of automatically driving the blending system...=0D=0A=0D=0A=0D=0A=09Ale=
x Walters wrote=0D=0A=09"If your 'eyebrow raising' is an interpolation betw=
een 2=0D=0Aanimations then you can use the t you are already using for blen=
ding=0D=0Abetween the two keyframes to drive the texture blend, this would =
work=0D=0Aover the whole texture, not just the local area of the eye"=0D=0A=0D=
=0A=0D=0A=09Unfortunately you cant really do this, because "t", your=0D=0Ai=
nterpolation=0D=0A=09between animation keyframes doesn't necessarily corres=
pond to=0D=0Athe amount=0D=0A=09of movement that is being applied to a bone=
=2E=0D=0A=09For example, you could have an animation raising the eyebrow al=
l=0D=0Athe way=0D=0A=09up, and an animation raising the eyebrow only half-w=
ay. In both=0D=0A=09animations, "t" is still just a linear interpolation be=
tween 0.0=0D=0A-> 1.0.=0D=0A=09Whereas we only want to blend the normal map=
 based on how far=0D=0Athe bone=0D=0A=09has moved as opposed to how far we =
are through the animation...=0D=0A=0D=0A=0D=0AI meant that in this case you=
 would need an 'amount of desired=0D=0Acreasyness' associated with the key =
frame or spline.=0D=0A=0D=0ATo calculate an interpolation value you need to=
 know both extents, if=0D=0Athe eyebrow can move at most 2cm upwards then y=
ou know that distance=0D=0Amoved / 2cm is the correct value of t. If you ha=
ve no explicit way of=0D=0Adetermining how far from the extent the movement=
 is then you need some=0D=0Aother upper bound quantifier. If designing the =
animation for a slight=0D=0Agrimace, a small amount of wrinkling would occu=
r on the forehead, there=0D=0Afor by attaching some kind of info, such as a=
 spline or keys to the=0D=0Aanimation to indicate the ammount of wrinkle th=
en you can use this=0D=0Ainconjunction with your normal inter key frame int=
erpolation controller.=0D=0AIt also becomes artist tunable.=0D=0A=0D=0AIn a=
ll honesty I didn't really answer your question as I assume you were=0D=0Ai=
ntending to come up with a way of determining the desired wrinkle=0D=0Apure=
ly from what is already in your pipeline. Namely something along the=0D=0Al=
ines of this set of data.=0D=0A=0D=0A1. vertex positions, start, current, p=
ossibly destination,=0D=0A2. t value of interpolation controller,=0D=0A3. b=
one weights if present,=0D=0A4. bone degree of freedom, if present.=0D=0A=0D=
=0ABasicly you need to identify something that will give you an upper bound=0D=
=0Aon the ammount of possible movement so you can identify that as the=0D=0A=
point of maximum wrinklyness. Then from the start and that upper bound=0D=0A=
working out t.=0D=0A=0D=0A=0D=0A=09One method I was considering was storing=
 information on two=0D=0Aposes....=0D=0A=09one with the character in the re=
laxed position (legs/arms=0D=0Aoutstretched,=0D=0A=09face relaxed), and the=
 second with the character in the most=0D=0Acreased=0D=0A=09position (legs/=
arms completely bent, face scrunched), and then=0D=0Alooking=0D=0A=09at eac=
h bone to find out how far I am between these extremes...=0D=0Ahowever=0D=0A=
=09this raises many many issues, such as bones that have many=0D=0Adegrees =
of=0D=0A=09freedom like shoulders...=0D=0A=0D=0A=0D=0AThat would be an inte=
resting idea, the complicated bone arrangements=0D=0Acould be a problem I a=
gree. Do you maintain degree of freedom=0D=0Ainformation for your bones, so=
 you could use ik perhaps=3F Or are they=0D=0Acomepltely free and movement =
is only controlled by animations=0D=0Aconstructed by the fair hands of our =
lovely friends the artists=3F If you=0D=0Ahave the IK info couldn't you com=
pare the bone to its maximum extents=0D=0Aand get your t from there=3F=20=0D=
=0A=0D=0AI guess attaching creasyness info to the bone keys would be more d=
ata=0D=0Aand would require artists to go back over work already done.=20=0D=
=0A=0D=0AI've got to go, but ill have a think, its an interesting problem! =
Just=0D=0Awaiting for Tom to do his usual, unless of course RAD havent thou=
ght of=0D=0Ait yet ;)=0D=0A=0D=0AAlex=0D=0A=0D=0A******************=0D=0ATh=
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