gdalgorithms-list

Re: [Algorithms] Bullets on walls

[Neal T. <ne...@ps...>]

Giovanni Bajo <ba...@pr...> writes:
> In DirectX, there is a ZBIAS stuff that let you set a priority order
> (integer) when Z matches. It is a renderstate. But looking at the caps, it
> is not supported in every boards I have tried. I heard it is an old
thingie
> of first Voodoo boards.

Yes, the support for zbias seems to be rather inconsistent.

> I had not found something similiar in OpenGL.

You may want to look at the 1.1 glPolygonOffset function.


Neal Tringham (Sick Puppies)

ne...@ps...
ne...@em...

RE: [Algorithms] Bullets on walls

[Giovanni B. <ba...@pr...>]

In DirectX, there is a ZBIAS stuff that let you set a priority order
(integer) when Z matches. It is a renderstate. But looking at the caps, it
is not supported in every boards I have tried. I heard it is an old thingie
of first Voodoo boards.
I had not found something similiar in OpenGL.

---
Giovanni Bajo
Lead Programmer

Protonic Interactive
www.protonic.net

a brand of Prograph Research S.r.l.
www.prograph.it


> -----Original Message-----
> From: gda...@li...
> [mailto:gda...@li...]On Behalf Of Angel
> Popov
> Sent: Friday, July 21, 2000 9:27 AM
> To: gda...@li...
> Subject: Re: [Algorithms] Bullets on walls
>
>
> > Hi!
> > I added wallmarks in my 3d engine but when I fire on the border
> of a wall
> I would like to clip the wallmark to the wall.
> >
> > I have some ideas but I think they are a bit slow... (manual clipping,
> texgen, stencil?)
> >
> > How do you do this?
> >
> > Thanks for any help!
>
> An extention like glDepthFunc( GL_ALMOST_EQUAL ) will be quite usefull for
> things like wallmarks and loosely projected shadows.
> Does anyone know if something like this is avaiable on current hardware?
>
>
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
>

Re: [Algorithms] interpolate between points in 3d space

[Ray <ra...@gu...>]

> Anceschi Mauro wrote:
> 
> Hi.
> I have a little problem in my 3D space game.
> When my ship "fire" from a cannon i use a new local axis for the new
> object i'm firing , for calculate the next point of the laser.
> But this works bad, and i  don't have much precision.
> So my question is:
> How can interpolate from 2 point in 3d?
> (x,y,z) and (x',y',z') (suppose the second is an enemy ship).
> 
> Thanks,
> 
> mauro

Hi,
What you could do is use a simple parametric equation.
for t=0.0 to 1.0
currentpoint = point0 + (point1-point0)*t;
where point0 = (x,y,z) and
point1 = (x',y',z')

when t = 0.0, you are at (x,y,z)
when t = 1.0, you are at (x',y',z')
when t = 0.5, you are half way between.

It can be broken down into:
newx = x + (x'-x)*t;
newy = y + (y'-y)*t;
newz = z + (z'-z)*t;

Hope that helps.

What you can do is depend t on your framerate to get a consistant
velocity.
This is effectively giving you a velocity of (point1-point0) per second.

That's my answer without telling you to do something completely
different like having a given velocity for your cannonfire and yadda
yadda, etc...

- Ray
ra...@gu...

[Algorithms] interpolate between points in 3d space

[Anceschi M. <anc...@li...>]

Hi.
I have a little problem in my 3D space game.
When my ship "fire" from a cannon i use a new local axis for the new =
object i'm firing , for calculate the next point of the laser.
But this works bad, and i  don't have much precision.
So my question is:
How can interpolate from 2 point in 3d?
(x,y,z) and (x',y',z') (suppose the second is an enemy ship).
=20
Thanks,
=20
mauro =20

Re: [Algorithms] Bullets on walls

[Angel P. <ju...@bi...>]

> Hi!
> I added wallmarks in my 3d engine but when I fire on the border of a wall
I would like to clip the wallmark to the wall.
>
> I have some ideas but I think they are a bit slow... (manual clipping,
texgen, stencil?)
>
> How do you do this?
>
> Thanks for any help!

An extention like glDepthFunc( GL_ALMOST_EQUAL ) will be quite usefull for
things like wallmarks and loosely projected shadows.
Does anyone know if something like this is avaiable on current hardware?

Re: [Algorithms] Bullets on walls

[Mark W. <mwa...@to...>]

An extension to Jaimi's method may be to render the bullet holes to an
overlay texture (of which you would have a maximum number) which is only
rendered *once* on-top of the wall. With complex texture mapping this is
obviously not possible, but perhaps for simple quads it would be acceptable
?

Perhaps some form of scalable solution - like use Jaimi's method for a small
number and when a threshold is reached, combine them into the single texture
as I've mentioned and repeat ... ??

Just my 2c worth ...

Mark

> In d3d, this is the way I do it:
>
> Create decals with a one pixel transparent border.
> Then, set the texture address mode to "Clamp".
> Calculate new UV coordinates for your decal based on the wall, instead
> of the Decal - then redraw the entire wall with your decal texture and
> new UV coordinates.
> This way you do not have to clip at all. I would assume you could
> do the same in OpenGL.
>
> Jaimi

[Algorithms] FOURCC encoded pixel data

[Blake S. <bse...@ro...>]

I'm getting passed pixel data that has been encoded
with the following FOURCC pixel formats:

MKFOURCC('I','4','2','0') /* planar YCrCb   */
MKFOURCC('Y','V','1','2') /* planar YVU420  */
MKFOURCC('Y','U','Y','2') /* packed YUV422  */
MKFOURCC('U','Y','V','Y') /* packed YUV422  */
MKFOURCC('Y','V','U','9') /* Intel YVU9     */
MKFOURCC('3','B','G','R') /* RGB-32 ??      */
MKFOURCC('B','G','R',' ') /* top-down RGB-24*/
MKFOURCC('6','B','G','R') /* RGB-16 565     */
MKFOURCC('5','B','G','R') /* RGB-16 555     */
MKFOURCC('T','I','B','8') /* RGB-8 w. pal-e */
MKFOURCC('2','V','U','Y') /* planar YCrCb   */
MKFOURCC('1','V','U','Y') /* ???            */
MKFOURCC('R','V','U','Y') /* ???            */

I'm getting passed the pixel array, a rectangle, one
of these FOURCC codes and a pixel bit count.

I need to blit these to a window, or convert them
to a BITMAPINFO struct so I can then blit or whatever.

I'm in a win32 environment, but I can't use directX.
Searching through MSDN seems to only refer to directX
routines that operate on pixel data in this format...

Does anyone know of a routine or lib that converts these
to something I can work with that is not DirectX based?

I could write conversions on my own, but I doubt they
would be very fast...

-Blake

[Algorithms] Mesh optimization

[John R. <jra...@ve...>]

Can anyone recommend some resources on how to 'clean-up' a mesh which has
suffered the insult and injury of having a rather violent boolean operation
performed on it?

Something which will detect T-junctions and split those offending polygons
up so that they will share vertices with their neighbors?

Is it as simple as detecting any vertice which lies on the edge of a face
and then splitting the face at that location?

Thanks,

John

[Algorithms] OBBs

[<Nik...@ao...>]

I recently finished writing a collision detection system for my engine (using 
OBBs); however I have been having trouble with the system not always 
detecting collisions.  I tested all of the functions separately to confirm 
their accuracy; yet this brought no avail.  I decided to work backwards to 
find the bug, and I used a function from the RAPID library which tests for 
disjointedness between two boxes.  Here is the description of the function:

This is a test between two boxes, box A and box B.  It is assumed that
the coordinate system is aligned and centered on box A.  The 3x3
matrix B specifies box B's orientation with respect to box A.
Specifically, the columns of B are the basis vectors (axis vectors) of
box B.  The center of box B is located at the vector T.  The
dimensions of box B are given in the array b.  The orientation and
placement of box A, in this coordinate system, are the identity matrix
and zero vector, respectively, so they need not be specified.  The
dimensions of box A are given in array a.
    obb_disjoint(double B[3][3], double T[3], double a[3], double b[3]);

I set up a situation in Max using two boxes, in which the collision detection 
failed, and I then entered the box data in by hand.  The result was that 
after putting box 2 in box 1's coordinate system, the matrix B was a 128 
degree rotation around the Z axis (or Max's Y axis).  The location of box 2 
in relation to box 1 was:
    T[0]= -5.853f;
    T[1]= -2.173f;
    T[2]= 3.842f;
And the dimensions (half-lengths) were:
    Bd[0]= 2;  Bd[1]= 4; Bd[2]= 4.5;
    Ad[0]= 4;  Ad[1]= 1; Ad[2]= 7.5;    
If you set this situation up in Max, it is obvious that the two boxes 
intersect (make sure to switch the Y & Z coordinates because of the 
difference in D3D and Max's CS, and multiply the half-lengths by 2 to get the 
actual dimensions).  Yet, RAPID's function reports that the boxes are 
disjoint.  Any help would be appreciated.

Thanks,
Nik...@ao...

Re: [Algorithms] Bullets on walls

[jason w. <jas...@po...>]

another stratagy that may work ok as a compramise: if you've already got a
lightmap on the world geometry, then do a subtexture update to the texture
in question, making some little marks on it.

it limits what you can do... I suspect it could be hard to get good blood
stain looking things. You'd also possibly get a framerate hit while someone
is shooting.. a bad situation. But it does avoid the overhead of rendering
seperate geometry.

and a final little diatribe on my part: I think in this next generation,
games that use world geometry only a little more detailed than the current,
and instead use all the rest of the geforce or whatever's few million
polygons for interactive effects like this... I think game engines that make
that choice will end up way better than games that just dump a huge high
poly world object at the T&L.

or to put it another way: what's better: a 500 poly character with a shadow
cast on the floor, or a 1000 poly char with no shadow. I think shadow wins.

Re: [Algorithms] Bullets on walls

[jason w. <jas...@po...>]

survey says:

BZZZZZZZZT

in an online action game, like say.. counterstrike.. decals become *vital*
to gameplay. you just can't see what you're doing otherwise.. situations
happen where two people are facing off on either side of a doorway of some
sort.. in that kind of fire fight, you can easily use the decals on the wall
behind you to guestimate your enemies line of visability, get right up by
it, and use it to your advantage

I would now consider these sorts of marring effects a required feature of
any FPS or real time tactics game.

jason

RE: [Algorithms] Bullets on walls

[Jaimi M. <ja...@al...>]

It's not *that* slow. Having a list of quads means you get into all
those z-fighting problems. Nothing that could not be overcame, of course,
but annoying nonetheless. 
I guess the reason that this works for me because my decals are 
usually very large and not very numerous (I use them for explosion marks, 
and for shadows). Still - I will try it out everyone elses way. 
Doesn't hurt to try new things. 

Jaimi


-----Original Message-----
This is really really slow -- your much better off having a list of
quads and rendering the bulletmarks as those...

Leathal.

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Re: [Algorithms] Bullets on walls

[<Lea...@en...>]

> Calculate new UV coordinates for your decal based on the wall, instead
> of the Decal - then redraw the entire wall with your decal texture and
> new UV coordinates.

This is really really slow -- your much better off having a list of
quads and rendering the bulletmarks as those...

Leathal.

RE: [Algorithms] Bullets on walls

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

Now you know why only the most efficient 3D engines provide battle damage.
Stephen has indicated the industry standard for adding damage to a texture.
It's not too expensive if you find the most efficient place to code it in
your engine...it's just an extra UV calc and blt, or discover a new way.  In
either way it's one of the features that really makes a difference...cause
without it it's like shooting blanks...think about some of the other
references with that phrase...and you'll see why it's unthinkable to go
without it.  :)

R&R

> From: Stephen J Baker [mailto:sj...@li...]
> 
> On Thu, 20 Jul 2000, Jaimi McEntire wrote:
> 
> > In d3d, this is the way I do it:
> > 
> > Create decals with a one pixel transparent border.
> > Then, set the texture address mode to "Clamp".
> > Calculate new UV coordinates for your decal based on the 
> wall, instead
> > of the Decal - then redraw the entire wall with your decal 
> texture and
> > new UV coordinates.
> > This way you do not have to clip at all. I would assume you could
> > do the same in OpenGL.
>  
> Doesn't this get a bit expensive when someone fires of an entire
> clip of ammo at one wall - and then walks right up to it to
> examine the damage?  Seems like each bullethole would be another
> complete overwrite of the entire wall...bye-bye pixel-fill rate!
> 
> 
> 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
> 
> 
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> 

RE: [Algorithms] Bullets on walls

[Jay S. <Ja...@va...>]

This was the first thing I tried for the bullet holes in Half-Life.  It's
really, really slow.  Once you have 3 or 4 bullet holes on a wall and a
player walks up to the wall you are redrawing the entire screen 5 or 6 times
(or more if you have complex materials).  This just doesn't scale if you
expect to have several decals on a single surface.  It's much better to clip
the decal polygons and draw them with polygon offset.

Jay

> -----Original Message-----
> From: Jaimi McEntire [mailto:ja...@al...]
> Sent: Thursday, July 20, 2000 1:01 PM
> To: gda...@li...
> Subject: RE: [Algorithms] Bullets on walls
> 
> 
> In d3d, this is the way I do it:
> 
> Create decals with a one pixel transparent border.
> Then, set the texture address mode to "Clamp".
> Calculate new UV coordinates for your decal based on the wall, instead
> of the Decal - then redraw the entire wall with your decal texture and
> new UV coordinates.
> This way you do not have to clip at all. I would assume you could
> do the same in OpenGL.
> 
> Jaimi
> 
> -----Original Message-----
> From: gda...@li...
> [mailto:gda...@li...]On Behalf Of
> Tiziano Lena
> Sent: Thursday, July 20, 2000 2:19 PM
> To: gda...@li...
> Subject: [Algorithms] Bullets on walls
> 
> 
> Hi!
> I added wallmarks in my 3d engine but when I fire on the 
> border of a wall I
> would like to clip the wallmark to the wall.
> 
> I have some ideas but I think they are a bit slow... (manual clipping,
> texgen, stencil?)
> 
> How do you do this?
> 
> Thanks for any help!
> 
> 
> 
> _______________________________________________
> 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] Bullets on walls

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

On Thu, 20 Jul 2000, Jaimi McEntire wrote:

> In d3d, this is the way I do it:
> 
> Create decals with a one pixel transparent border.
> Then, set the texture address mode to "Clamp".
> Calculate new UV coordinates for your decal based on the wall, instead
> of the Decal - then redraw the entire wall with your decal texture and
> new UV coordinates.
> This way you do not have to clip at all. I would assume you could
> do the same in OpenGL.
 
Doesn't this get a bit expensive when someone fires of an entire
clip of ammo at one wall - and then walks right up to it to
examine the damage?  Seems like each bullethole would be another
complete overwrite of the entire wall...bye-bye pixel-fill rate!


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] Bullets on walls

[Kent Q. <ken...@co...>]

Sleazy...but -- they missed, right? So it doesn't REALLY matter where
the bullet hits...

Move it over until it's all the way onto the wall and don't worry about
it.

:-)

	Kent

Tiziano Lena wrote:
> 
> Hi!
> I added wallmarks in my 3d engine but when I fire on the border of a wall I would like to clip the wallmark to the wall.
> 
> I have some ideas but I think they are a bit slow... (manual clipping, texgen, stencil?)
> 
> How do you do this?

-- 
-----------------------------------------------------------------------
Kent Quirk                   | CogniToy: Intelligent toys...
Game Designer                |           for intelligent minds.
ken...@co...      | http://www.cognitoy.com/     
_____________________________|_________________________________________

RE: [Algorithms] Bullets on walls

[Jaimi M. <ja...@al...>]

In d3d, this is the way I do it:

Create decals with a one pixel transparent border.
Then, set the texture address mode to "Clamp".
Calculate new UV coordinates for your decal based on the wall, instead
of the Decal - then redraw the entire wall with your decal texture and
new UV coordinates.
This way you do not have to clip at all. I would assume you could
do the same in OpenGL.

Jaimi

-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of
Tiziano Lena
Sent: Thursday, July 20, 2000 2:19 PM
To: gda...@li...
Subject: [Algorithms] Bullets on walls


Hi!
I added wallmarks in my 3d engine but when I fire on the border of a wall I
would like to clip the wallmark to the wall.

I have some ideas but I think they are a bit slow... (manual clipping,
texgen, stencil?)

How do you do this?

Thanks for any help!



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

[Algorithms] Bullets on walls

[Tiziano L. <tl...@fl...>]

Hi!
I added wallmarks in my 3d engine but when I fire on the border of a wall I would like to clip the wallmark to the wall. 

I have some ideas but I think they are a bit slow... (manual clipping, texgen, stencil?)

How do you do this?

Thanks for any help!

[Algorithms] Machine specific optimization

[Kevin L. <lac...@in...>]

What wouild the c++ code look like that polls the cpu ? to see what type
of stucture I want to use? For example using the mmx vector and matrix
classes etc.

Thanks
Kevin

-- 

RE: [Algorithms] GUIDs

[Scott B. <sc...@ga...>]

Win32 GUID's are based on the algorithm used by OSF's DCE. Here's a starting
point:

http://msdn.microsoft.com/library/default.asp?URL=/library/books/inole/S10E8
.HTM

Check out the last paragraph...talks about where to find the actual spec for
the algorithm.

Scott

-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of Matthew
Davies
Sent: Thursday, July 20, 2000 1:59 AM
To: Algorithms List (E-mail)
Subject: [Algorithms] GUIDs


Hi,

Does anyone know the algorithm or have source code describing the way
CoGuidCreate or UuidCreate generates the GUIDs?  Or perhaps there's a cross
platform solution to generating globally unique identifiers?

Regards,
Matt J. Davies
Programmer
Acclaim Studios Ltd.
Lansdown Road,
Cheltenham,
Gloucestershire,
United Kingdom,
GL50 2JA.
Tel: +44 (0) 1242 533 682
Fax: +44 (0) 1242 533 700

Re: [Algorithms] 3DS woes.

[Marco C. <ma...@pr...>]

----- Original Message -----
From: Leigh McRae <lei...@ro...>
To: <gda...@li...>
Sent: Wednesday, July 19, 2000 3:21 PM
Subject: [Algorithms] 3DS woes.


>   Sorry if OT but I have spent way too long on this 3ds exporter thing.
>
>   I wrote some code to read a 3ds file and things work for the most part.
I
> have the basic models and texture mapping working right but somethings
> wacked.  I have a  house.3ds file that is basicly a box and roof but the
> roof never lands on top of the house.
>The NVidia toolkit viewer also doesn't show the roof right.  Is this a
common thing?
>   Any help on getting a model out of MAX would be much appreciated and I
can
> give my semi-broken code out if it helps fix it.
> Leigh McRae

I found similar problems, common with all other viewers...I fixed it
removing history; if you remove history from 3dS MAX and then export the
.3ds model,it should work fine...


Marco Corbetta
ma...@pr...




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

Re: [Algorithms] GUIDs

[Kent Q. <ken...@co...>]

I don't have the details, but as I recall, the general idea was to
combine the network MAC address of the machine generating the GUID
(which is a 48-bit unique number) with a version of the date and time
down to the millisecond. No two machines with a network card should ever
be able to generate the same GUIDs that way (as long as you don't
generate more than one per millisecond, anyway!).

For machines that don't have a network card, there was some other way of
getting the 48-bit ID, but I forget what it is.

> Matthew Davies wrote:
> 
> Hi,
> 
> Does anyone know the algorithm or have source code describing the way
> CoGuidCreate or UuidCreate generates the GUIDs?  Or perhaps there's a
> cross platform solution to generating globally unique identifiers?
> 

-- 
-----------------------------------------------------------------------
Kent Quirk                   | CogniToy: Intelligent toys...
Game Designer                |           for intelligent minds.
ken...@co...      | http://www.cognitoy.com/     
_____________________________|_________________________________________

Re: [Algorithms] GUIDs

[Davide P. <da...@pr...>]

>Does anyone know the algorithm or have source code describing the way
>CoGuidCreate or UuidCreate generates the GUIDs?  Or perhaps there's a =
cross
>platform solution to generating globally unique identifiers?

MSDN library samples...

VC98\mfc\utility\guidgen

Davide Pirola

www.prograph.it
www.protonic.net

Re: [Algorithms] 3DS woes Summary.

[Leigh M. <lei...@ro...>]

  Thanks all for solving this problem.  Not sure why I still expect
published code to work.  Just to sum up what I have concluded from this
whole 3ds mess:

1) The 3ds export plugin for MAX R3.1 does indeed seem to be broken as I
couldn't find anything that would display the 3ds file correctly.  It was
found that a Lightwave 3ds worked fine.

2) The 3ds format isn't worth the trouble unless you must have it for some
compatability issue.  DOS 8.3 file naming and the limit of 16bit indices was
enough to make me leave the 3ds format.

3) There is a R3_SKELETON for export plugins found in the HOWTO directory
that gives you the best starting point.

4) The ASCII export plugin is the best reference for actually writing the
plugin.

Leigh McRae


----- Original Message -----
From: Robert Dibley <RD...@ac...>
To: <gda...@li...>
Sent: Wednesday, July 19, 2000 12:10 PM
Subject: RE: [Algorithms] 3DS woes.


> > I have a  house.3ds file that is basicly a box and roof but the
> > roof never lands on top of the house.  If I join the roof and box then
it
> > works ok.
>
> Are you by any chance using the MAX exporter that writes 3DS files ?
> If so, then that may be your problem - when I looked at it, it seemed to
be
> bugged.  Something to do with using the wrong matrix I think.  Something
> like GetNodeTM being used where GetObjectTM should have been perhaps ?
>
> hope thats some small help,
>
> Robert
>
> _______________________________________________
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>