So here's a thing I've never understood... Why do so many 3D games have 
trouble getting two objects to touch each other?

For example, that scene from FarCry 3 where you present Citra with the 
knife. It's pretty-much a cut-scene, yet even here, the mighty CryEngine 
seems to be struggling to get the knife to rest *on* Citra's hands, 
rather than partially intersecting them.

Why is that?

I can understand that it's hard to do the physics of simulating complex 
non-flat (and possibly deformable) objects resting on each other. (Hence 
the ubiquitous flailing rag-dolls.) But this is a pre-scripted 
animation. You've GOT the coordinates of Citra's hands RIGHT THERE! (And 
they're always the same.) How hard can it be?

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On Sun, 11 Jan 2015 17:04:21 +0200, Orchid Win7 v1 <voi### [at] devnull> wrote:

> So here's a thing I've never understood... Why do so many 3D games have  
> trouble getting two objects to touch each other?
>
> For example, that scene from FarCry 3 where you present Citra with the  
> knife. It's pretty-much a cut-scene, yet even here, the mighty CryEngine  
> seems to be struggling to get the knife to rest *on* Citra's hands,  
> rather than partially intersecting them.

Not CryEngine
Dunia Engine 2

>
> Why is that?
>
> I can understand that it's hard to do the physics of simulating complex  
> non-flat (and possibly deformable) objects resting on each other. (Hence  
> the ubiquitous flailing rag-dolls.) But this is a pre-scripted  
> animation. You've GOT the coordinates of Citra's hands RIGHT THERE! (And  
> they're always the same.) How hard can it be?

Probably deadlines or laziness or both.

-- 
-Nekar Xenos-

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> For example, that scene from FarCry 3 where you present Citra with the
> knife. It's pretty-much a cut-scene, yet even here, the mighty CryEngine
> seems to be struggling to get the knife to rest *on* Citra's hands,
> rather than partially intersecting them.
>
> Why is that?
>
> I can understand that it's hard to do the physics of simulating complex
> non-flat (and possibly deformable) objects resting on each other. (Hence
> the ubiquitous flailing rag-dolls.) But this is a pre-scripted
> animation. You've GOT the coordinates of Citra's hands RIGHT THERE! (And
> they're always the same.) How hard can it be?

As Nekar replied already, I'm pretty sure the animator in question would 
not be allowed to spend any more than the absolute minimum amount of 
time to get one object in one part of one cut-scene looking ok. They 
might even "rough out" any special objects/movements and then only come 
back and improve them if there is time at the end whilst waiting for 
other parts to complete ("must haves" vs "nice to haves").

Then you've got the technical challenge of a rigid object pressing 
against a very soft object. If you treated the hand as rigid then it 
might look stranger than allowing a bit of intersection, IDK. I can't 
say I remember noticing any defect at that point in the cut-scene, is 
that the last bit at the end of the game or earlier?

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> As Nekar replied already, I'm pretty sure the animator in question would
> not be allowed to spend any more than the absolute minimum amount of
> time to get one object in one part of one cut-scene looking ok. They
> might even "rough out" any special objects/movements and then only come
> back and improve them if there is time at the end whilst waiting for
> other parts to complete ("must haves" vs "nice to haves").

As I say, I would have thought it would be *easier* to just set the 
coordinates of the knife to be equal to the coordinates of the hands. 
What they *actually* did seems like more effort.

> Then you've got the technical challenge of a rigid object pressing
> against a very soft object. If you treated the hand as rigid then it
> might look stranger than allowing a bit of intersection, IDK. I can't
> say I remember noticing any defect at that point in the cut-scene, is
> that the last bit at the end of the game or earlier?

It's not just this one particular game. It's every 3D game I've ever 
played where you see one character hand something to another. It's 
weird; when Alyx draws her gun, you never see the gun clipping through 
her fingers. But when she picks an object up off the table, the object 
doesn't *quite* follow the motion of her hands exactly... Why would you 
bother animating those moves twice?

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On 17/01/2015 12:36, Orchid Win7 v1 wrote:

> It's not just this one particular game. It's every 3D game I've ever
> played where you see one character hand something to another. It's
> weird; when Alyx draws her gun, you never see the gun clipping through
> her fingers. But when she picks an object up off the table, the object
> doesn't *quite* follow the motion of her hands exactly... Why would you
> bother animating those moves twice?

I would imagine that when she draws her gun. That is a set action and 
the motion would be defined in detail. When she picks an object off the 
table. The object could be one of many and oriented randomly. So a 
simpler and less accurate set of motions used for that.
-- 

Regards
     Stephen

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