gdalgorithms-list

RE: [Algorithms] Return of the front clip plane

[Steve W. <Ste...@im...>]

> -----Original Message-----
> From: Jason Zisk [mailto:zi...@n-...]
> 
> Another solution is to just make your player's bounding 
> volume larger so you can't get close enough to stuff to
> clip into it, this works okay but I find that you have 
> to keep the player from getting closer than 3 units with 
> a 1 unit clip because of viewport rotation (just keeping the 
> player 1 unit away is fine if you are staring straight at a 
> wall but as soon as you rotate the edges of your viewport 
> will clip it).
> 

For my FPS I used a wall that I walked up to then looked up and down, then
adjusted my collision detection to prevent the player's view from clipping
the wall simply because of the view angle.  It seems to work fine...I
wouldn't want to get into changing the viewport dimensions cause wouldn't it
distort the scene?  I'd reserve changing viewport dimensions for special
effects like underwater wooziness.

R&R

RE: [Algorithms] Return of the front clip plane

[Tom F. <to...@mu...>]

Moving the near (and possibly far - depends on your app) clip planes
dynamically works very well indeed. Yes, there is the slight artifact that
walking past a tree affects the Z precision of the far-off building that
you're actually looking at, but then it's pretty hard to think of any system
that will do it any better, apart from the Z-partition trick (which is
expensive in some cases - though dead easy for flight sims).

Tom Forsyth - Muckyfoot bloke.
Whizzing and pasting and pooting through the day.

> -----Original Message-----
> From: Steve Wood [mailto:Ste...@im...]
> Sent: 03 August 2000 20:09
> To: 'gda...@li...'
> Subject: RE: [Algorithms] Return of the front clip plane
> 
> 
> > -----Original Message-----
> > From: Jason Zisk [mailto:zi...@n-...]
> > 
> > Another solution is to just make your player's bounding 
> > volume larger so you can't get close enough to stuff to
> > clip into it, this works okay but I find that you have 
> > to keep the player from getting closer than 3 units with 
> > a 1 unit clip because of viewport rotation (just keeping the 
> > player 1 unit away is fine if you are staring straight at a 
> > wall but as soon as you rotate the edges of your viewport 
> > will clip it).
> > 
> 
> For my FPS I used a wall that I walked up to then looked up 
> and down, then
> adjusted my collision detection to prevent the player's view 
> from clipping
> the wall simply because of the view angle.  It seems to work fine...I
> wouldn't want to get into changing the viewport dimensions 
> cause wouldn't it
> distort the scene?  I'd reserve changing viewport dimensions 
> for special
> effects like underwater wooziness.
> 
> R&R
> 
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> 

RE: [Algorithms] Return of the front clip plane

[Stephen J B. <sj...@li...>]

On Thu, 3 Aug 2000, Tom Forsyth wrote:

> Moving the near (and possibly far - depends on your app) clip planes
> dynamically works very well indeed. Yes, there is the slight artifact that
> walking past a tree affects the Z precision of the far-off building that
> you're actually looking at, but then it's pretty hard to think of any system
> that will do it any better, apart from the Z-partition trick (which is
> expensive in some cases - though dead easy for flight sims).
 
I think you want to limit the maximum value for Z near too - and doing that
at some reasonable distance (like 3 feet say) should minimise the effect
of walking past a tree.  You could also only pull the range in closer
when the object that's about to be clipped is inside the field-of-view.

At any rate, the need to not clip out the ground you are standing on
limits the maximum Z-near that you can achieve.

Steve Baker                      (817)619-2657 (Vox/Vox-Mail)
L3Com/Link Simulation & Training (817)619-2466 (Fax)
Work: sj...@li...           http://www.link.com
Home: sjb...@ai...       http://web2.airmail.net/sjbaker1

RE: [Algorithms] Return of the front clip plane

[Feltman, H. <Fe...@se...>]

So how does this sound:

- Create a frustum which matches your graphics API's frustum
with the exception of the near plane; for this, use the minimum
near plane you can handle.

- Clip world geometry (or a bounding version) to this frustum
manually just like the good old days.

- Use the closest clipped point of "whatever is left after clipping"
to the eye plane as the distance for the near plane for a new
frustum, send this frustum to the graphics API, and draw the
world geometry for this frame.

I'm sure it would work; is this the way you did it?

Hamilton Feltman
SEGA AMUS/ARCADE
www.sega.com/alienfront

> -----Original Message-----
> From:	Tom Forsyth [SMTP:to...@mu...]
> Sent:	Thursday, August 03, 2000 12:46 PM
> To:	gda...@li...
> Subject:	RE: [Algorithms] Return of the front clip plane
> 
> Moving the near (and possibly far - depends on your app) clip planes
> dynamically works very well indeed. Yes, there is the slight artifact that
> walking past a tree affects the Z precision of the far-off building that
> you're actually looking at, but then it's pretty hard to think of any
> system
> that will do it any better, apart from the Z-partition trick (which is
> expensive in some cases - though dead easy for flight sims).
> 
> Tom Forsyth - Muckyfoot bloke.
> Whizzing and pasting and pooting through the day.
> 
> > -----Original Message-----
> > From: Steve Wood [mailto:Ste...@im...]
> > Sent: 03 August 2000 20:09
> > To: 'gda...@li...'
> > Subject: RE: [Algorithms] Return of the front clip plane
> > 
> > 
> > > -----Original Message-----
> > > From: Jason Zisk [mailto:zi...@n-...]
> > > 
> > > Another solution is to just make your player's bounding 
> > > volume larger so you can't get close enough to stuff to
> > > clip into it, this works okay but I find that you have 
> > > to keep the player from getting closer than 3 units with 
> > > a 1 unit clip because of viewport rotation (just keeping the 
> > > player 1 unit away is fine if you are staring straight at a 
> > > wall but as soon as you rotate the edges of your viewport 
> > > will clip it).
> > > 
> > 
> > For my FPS I used a wall that I walked up to then looked up 
> > and down, then
> > adjusted my collision detection to prevent the player's view 
> > from clipping
> > the wall simply because of the view angle.  It seems to work fine...I
> > wouldn't want to get into changing the viewport dimensions 
> > cause wouldn't it
> > distort the scene?  I'd reserve changing viewport dimensions 
> > for special
> > effects like underwater wooziness.
> > 
> > R&R
> > 
> > _______________________________________________
> > GDAlgorithms-list mailing list
> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> > 
> 
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

RE: [Algorithms] Return of the front clip plane

[Robert D. <RD...@ac...>]

a completely mad idea, but if this is first person, then make it really
first person ... attach the camera to the front of the viewing persons head,
and when they turn around the camera stays on the front of the head, and
hence moves away from the wall.  For a real life comparison, walk up to a
wall and turn around when you are touching it.  You will now have your head
a long way from the wall.  Just because people are not used to their
characters in games behaving like real world ones doesn't mean they
shouldn't, and maybe this is one case where if they did it would be better.

Rob

-----Original Message-----
From: Jason Zisk [mailto:zi...@n-...]
Sent: 03 August 2000 21:08
To: gda...@li...
Subject: Re: [Algorithms] Return of the front clip plane


Its wierd, for a wall this method works fine.  But for something smaller
like a tree it "feels" wrong, like you are colliding too early.  I guess its
because you can see the stuff around the tree so you have a frame of
reference?

- Jason Zisk
- nFusion Interactive LLC


----- Original Message -----
From: "Steve Wood" <Ste...@im...>
To: <gda...@li...>
Sent: Thursday, August 03, 2000 3:09 PM
Subject: RE: [Algorithms] Return of the front clip plane


> > -----Original Message-----
> > From: Jason Zisk [mailto:zi...@n-...]
> >
> > Another solution is to just make your player's bounding
> > volume larger so you can't get close enough to stuff to
> > clip into it, this works okay but I find that you have
> > to keep the player from getting closer than 3 units with
> > a 1 unit clip because of viewport rotation (just keeping the
> > player 1 unit away is fine if you are staring straight at a
> > wall but as soon as you rotate the edges of your viewport
> > will clip it).
> >
>
> For my FPS I used a wall that I walked up to then looked up and down, then
> adjusted my collision detection to prevent the player's view from clipping
> the wall simply because of the view angle.  It seems to work fine...I
> wouldn't want to get into changing the viewport dimensions cause wouldn't
it
> distort the scene?  I'd reserve changing viewport dimensions for special
> effects like underwater wooziness.
>
> R&R
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list


_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

Re: [Algorithms] Return of the front clip plane

[Jason Z. <zi...@n-...>]

Well this is the same thing as just making the player's collision radius
smaller.  You'd still get too close to the wall and clip it out if you
looked up/down.  Maybe not left/right though, which might be where the
thought came from.  :)

I could just not let the player look up and down, doom got away with it
right?  ;)

- Jason Zisk
- nFusion Interactive LLC


----- Original Message -----
From: "Robert Dibley" <RD...@ac...>
To: <gda...@li...>
Sent: Thursday, August 03, 2000 5:28 PM
Subject: RE: [Algorithms] Return of the front clip plane


> a completely mad idea, but if this is first person, then make it really
> first person ... attach the camera to the front of the viewing persons
head,
> and when they turn around the camera stays on the front of the head, and
> hence moves away from the wall.  For a real life comparison, walk up to a
> wall and turn around when you are touching it.  You will now have your
head
> a long way from the wall.  Just because people are not used to their
> characters in games behaving like real world ones doesn't mean they
> shouldn't, and maybe this is one case where if they did it would be
better.
>
> Rob
>
> -----Original Message-----
> From: Jason Zisk [mailto:zi...@n-...]
> Sent: 03 August 2000 21:08
> To: gda...@li...
> Subject: Re: [Algorithms] Return of the front clip plane
>
>
> Its wierd, for a wall this method works fine.  But for something smaller
> like a tree it "feels" wrong, like you are colliding too early.  I guess
its
> because you can see the stuff around the tree so you have a frame of
> reference?
>
> - Jason Zisk
> - nFusion Interactive LLC
>
>
> ----- Original Message -----
> From: "Steve Wood" <Ste...@im...>
> To: <gda...@li...>
> Sent: Thursday, August 03, 2000 3:09 PM
> Subject: RE: [Algorithms] Return of the front clip plane
>
>
> > > -----Original Message-----
> > > From: Jason Zisk [mailto:zi...@n-...]
> > >
> > > Another solution is to just make your player's bounding
> > > volume larger so you can't get close enough to stuff to
> > > clip into it, this works okay but I find that you have
> > > to keep the player from getting closer than 3 units with
> > > a 1 unit clip because of viewport rotation (just keeping the
> > > player 1 unit away is fine if you are staring straight at a
> > > wall but as soon as you rotate the edges of your viewport
> > > will clip it).
> > >
> >
> > For my FPS I used a wall that I walked up to then looked up and down,
then
> > adjusted my collision detection to prevent the player's view from
clipping
> > the wall simply because of the view angle.  It seems to work fine...I
> > wouldn't want to get into changing the viewport dimensions cause
wouldn't
> it
> > distort the scene?  I'd reserve changing viewport dimensions for special
> > effects like underwater wooziness.
> >
> > R&R
> >
> > _______________________________________________
> > GDAlgorithms-list mailing list
> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

RE: [Algorithms] Return of the front clip plane

[Robert D. <RD...@ac...>]

You could just apply real world stuff to it....

look up, you head tilts back, so your eyes will pull away from the wall.

look down, when standing with your nose against a wall and you hit the wall,
so you either collide and can't look down when against a wall or if thats
going to upset people either IK your body so the head is touching the wall,
or move the body back.

either way, in real life you cannot look down with your eyeball touching the
wall, because you aren't built that way, so applying similar limitations in
a game is not unreasonable.

Rob

-----Original Message-----
From: Jason Zisk [mailto:zi...@n-...]
Sent: 03 August 2000 23:32
To: gda...@li...
Subject: Re: [Algorithms] Return of the front clip plane


Well this is the same thing as just making the player's collision radius
smaller.  You'd still get too close to the wall and clip it out if you
looked up/down.  Maybe not left/right though, which might be where the
thought came from.  :)

I could just not let the player look up and down, doom got away with it
right?  ;)

- Jason Zisk
- nFusion Interactive LLC


----- Original Message -----
From: "Robert Dibley" <RD...@ac...>
To: <gda...@li...>
Sent: Thursday, August 03, 2000 5:28 PM
Subject: RE: [Algorithms] Return of the front clip plane


> a completely mad idea, but if this is first person, then make it really
> first person ... attach the camera to the front of the viewing persons
head,
> and when they turn around the camera stays on the front of the head, and
> hence moves away from the wall.  For a real life comparison, walk up to a
> wall and turn around when you are touching it.  You will now have your
head
> a long way from the wall.  Just because people are not used to their
> characters in games behaving like real world ones doesn't mean they
> shouldn't, and maybe this is one case where if they did it would be
better.
>
> Rob
>
> -----Original Message-----
> From: Jason Zisk [mailto:zi...@n-...]
> Sent: 03 August 2000 21:08
> To: gda...@li...
> Subject: Re: [Algorithms] Return of the front clip plane
>
>
> Its wierd, for a wall this method works fine.  But for something smaller
> like a tree it "feels" wrong, like you are colliding too early.  I guess
its
> because you can see the stuff around the tree so you have a frame of
> reference?
>
> - Jason Zisk
> - nFusion Interactive LLC
>
>
> ----- Original Message -----
> From: "Steve Wood" <Ste...@im...>
> To: <gda...@li...>
> Sent: Thursday, August 03, 2000 3:09 PM
> Subject: RE: [Algorithms] Return of the front clip plane
>
>
> > > -----Original Message-----
> > > From: Jason Zisk [mailto:zi...@n-...]
> > >
> > > Another solution is to just make your player's bounding
> > > volume larger so you can't get close enough to stuff to
> > > clip into it, this works okay but I find that you have
> > > to keep the player from getting closer than 3 units with
> > > a 1 unit clip because of viewport rotation (just keeping the
> > > player 1 unit away is fine if you are staring straight at a
> > > wall but as soon as you rotate the edges of your viewport
> > > will clip it).
> > >
> >
> > For my FPS I used a wall that I walked up to then looked up and down,
then
> > adjusted my collision detection to prevent the player's view from
clipping
> > the wall simply because of the view angle.  It seems to work fine...I
> > wouldn't want to get into changing the viewport dimensions cause
wouldn't
> it
> > distort the scene?  I'd reserve changing viewport dimensions for special
> > effects like underwater wooziness.
> >
> > R&R
> >
> > _______________________________________________
> > GDAlgorithms-list mailing list
> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list


_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

RE: [Algorithms] Return of the front clip plane

[Tom F. <to...@mu...>]

Hmmmm... I like the idea in principle - only the very near stuff (which is
hopefully quite rare) gets the extra clipping stuff, and even when it does
happen, the normal and far distance stuff isn't affected. Unfortunately, any
clipping imprecision is going to be very obvious since the objects are so
close to the camera. It might be better to move the near clip plane a bit
further away in these cases, so that any imprecision is moved further away
from the camera.

So under normal circumstances, your NCP is, say, 10m away. If anything comes
closer than 10m, you do the clipping to a plane 50m away and do Hamilton's
two-frustum trick. Maybe that'll result in fewer possible tears along the
clip lines.

Tom Forsyth - Muckyfoot bloke.
Whizzing and pasting and pooting through the day.

> -----Original Message-----
> From: Feltman, Hamilton [mailto:Fe...@se...]
> Sent: 03 August 2000 21:26
> To: 'gda...@li...'
> Subject: RE: [Algorithms] Return of the front clip plane
> 
> 
> 
> So how does this sound:
> 
> - Create a frustum which matches your graphics API's frustum
> with the exception of the near plane; for this, use the minimum
> near plane you can handle.
> 
> - Clip world geometry (or a bounding version) to this frustum
> manually just like the good old days.
> 
> - Use the closest clipped point of "whatever is left after clipping"
> to the eye plane as the distance for the near plane for a new
> frustum, send this frustum to the graphics API, and draw the
> world geometry for this frame.
> 
> I'm sure it would work; is this the way you did it?
> 
> Hamilton Feltman
> SEGA AMUS/ARCADE
> www.sega.com/alienfront
> 
> > -----Original Message-----
> > From:	Tom Forsyth [SMTP:to...@mu...]
> > Sent:	Thursday, August 03, 2000 12:46 PM
> > To:	gda...@li...
> > Subject:	RE: [Algorithms] Return of the front clip plane
> > 
> > Moving the near (and possibly far - depends on your app) clip planes
> > dynamically works very well indeed. Yes, there is the 
> slight artifact that
> > walking past a tree affects the Z precision of the far-off 
> building that
> > you're actually looking at, but then it's pretty hard to 
> think of any
> > system
> > that will do it any better, apart from the Z-partition 
> trick (which is
> > expensive in some cases - though dead easy for flight sims).
> > 
> > Tom Forsyth - Muckyfoot bloke.
> > Whizzing and pasting and pooting through the day.
> > 
> > > -----Original Message-----
> > > From: Steve Wood [mailto:Ste...@im...]
> > > Sent: 03 August 2000 20:09
> > > To: 'gda...@li...'
> > > Subject: RE: [Algorithms] Return of the front clip plane
> > > 
> > > 
> > > > -----Original Message-----
> > > > From: Jason Zisk [mailto:zi...@n-...]
> > > > 
> > > > Another solution is to just make your player's bounding 
> > > > volume larger so you can't get close enough to stuff to
> > > > clip into it, this works okay but I find that you have 
> > > > to keep the player from getting closer than 3 units with 
> > > > a 1 unit clip because of viewport rotation (just keeping the 
> > > > player 1 unit away is fine if you are staring straight at a 
> > > > wall but as soon as you rotate the edges of your viewport 
> > > > will clip it).
> > > > 
> > > 
> > > For my FPS I used a wall that I walked up to then looked up 
> > > and down, then
> > > adjusted my collision detection to prevent the player's view 
> > > from clipping
> > > the wall simply because of the view angle.  It seems to 
> work fine...I
> > > wouldn't want to get into changing the viewport dimensions 
> > > cause wouldn't it
> > > distort the scene?  I'd reserve changing viewport dimensions 
> > > for special
> > > effects like underwater wooziness.
> > > 
> > > R&R
> > > 
> > > _______________________________________________
> > > GDAlgorithms-list mailing list
> > > GDA...@li...
> > > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> > > 
> > 
> > _______________________________________________
> > GDAlgorithms-list mailing list
> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> 
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> 

Re: [Algorithms] Return of the front clip plane

[Jason Z. <zi...@n-...>]

Its wierd, for a wall this method works fine.  But for something smaller
like a tree it "feels" wrong, like you are colliding too early.  I guess its
because you can see the stuff around the tree so you have a frame of
reference?

- Jason Zisk
- nFusion Interactive LLC


----- Original Message -----
From: "Steve Wood" <Ste...@im...>
To: <gda...@li...>
Sent: Thursday, August 03, 2000 3:09 PM
Subject: RE: [Algorithms] Return of the front clip plane


> > -----Original Message-----
> > From: Jason Zisk [mailto:zi...@n-...]
> >
> > Another solution is to just make your player's bounding
> > volume larger so you can't get close enough to stuff to
> > clip into it, this works okay but I find that you have
> > to keep the player from getting closer than 3 units with
> > a 1 unit clip because of viewport rotation (just keeping the
> > player 1 unit away is fine if you are staring straight at a
> > wall but as soon as you rotate the edges of your viewport
> > will clip it).
> >
>
> For my FPS I used a wall that I walked up to then looked up and down, then
> adjusted my collision detection to prevent the player's view from clipping
> the wall simply because of the view angle.  It seems to work fine...I
> wouldn't want to get into changing the viewport dimensions cause wouldn't
it
> distort the scene?  I'd reserve changing viewport dimensions for special
> effects like underwater wooziness.
>
> R&R
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list