Need info for some nifty tricks

Need info for some nifty tricks

Post by Chri » Thu, 27 May 1999 04:00:00



Ive been playing with OpenGL for a while now and I have a few things I
have seen in games that I would like some info so I can experiment with
them.

1) volumetric lighting - is this what the dusty yellow lighting in the
first level of Unreal is ? Ive heard or various methods to achieve this
effect, including tracing from the point of view to a fog volume object
and measuring the length of intersection to generate a fog map of sorts.
Seems kind of expensive.  How does Unreal do it ? is there a way to make
use of the hardwares linear fogging abilities? Maybe rendering a
transparent sphere with fog turned on after rendering the scene with fog
off ? etc.

2) Unreal's shadows - again the first area, there are shadows projected
from the spinning fans in the ceiling. I am going to assume this is also
some sort of animated light/shadow  map since it only seems to render on
planar surfaces. ?

3) underwater shimmering - again, lightmaps ?

I need some more info on the BSP and PVS system used for drawing scenes
in games. I understand the basics but I still need to tie everything
together.
Does this system work the same for outdoor terrain oriented scenes such
as those in tribes?

Also I would like some info on collision bounding within a game map, ie:
cant walk through pillars, you walk upward when going up a slope, have
to crouch to go under things, etc. In tile based 2D games youd have an
array the same as the tile array with properties for each tile. What is
the standard way to make a 3D world physically solid ? esp important are
outdoor terrains of rolling hills where the player can move up and down
as it walks across the ground, something like Zelda 64.
All the special FX seem to involve lightmaps. I would like some info on
how to create static lightmaps at map compilation, and managing dynamic
light maps from say, shadows, rockets, etc, and how these are applied to
the scene.

And lastly, what order is best for a rendering pipeline ? I would think
drawing the level first, applying all lightmaps, textures, etc, then
drawing all objects and players, casting shadows, and last any fancy
atmospheric effects.

I dont expect any one indivudual to answer all these questions, so if
anyone can address any of these topics that would be great. Thanks

Chris

 
 
 

Need info for some nifty tricks

Post by Ian » Fri, 28 May 1999 04:00:00


Hi,


>Ive been playing with OpenGL for a while now and I have a few things I
>have seen in games that I would like some info so I can experiment with
>them.
>1) volumetric lighting - is this what the dusty yellow lighting in the
>first level of Unreal is ? Ive heard or various methods to achieve this
>effect, including tracing from the point of view to a fog volume object
>and measuring the length of intersection to generate a fog map of sorts.
>Seems kind of expensive.  How does Unreal do it ? is there a way to make
>use of the hardwares linear fogging abilities? Maybe rendering a
>transparent sphere with fog turned on after rendering the scene with fog
>off ? etc.

See volumetric shadows:
(Hilf-life I doubt does volumetric lighting,
just some transparent geometry spinning around I'd guess
looks real nice though! :) )

Quote:>2) Unreal's shadows - again the first area, there are shadows projected
>from the spinning fans in the ceiling. I am going to assume this is also
>some sort of animated light/shadow  map since it only seems to render on
>planar surfaces. ?

haven't seen unreal's shadows, there are lots of methods to calculate
shadows,
similar to the algorithms for projecting spot lights etc..

Shadow Volumes in combination with stencil buffers and
half a dozen passes over geometry, are used to do volumetric shadow effects.

Quote:>3) underwater shimmering - again, lightmaps ?

I suspect they are just warping the vertexes
through a sine wave of small amplitude to create the warbling effect.

Quote:>I need some more info on the BSP and PVS system used for drawing scenes
>in games. I understand the basics but I still need to tie everything
>together.

The BSP tree FAQ is easy to find, go to altavista and but "BSP Tree FAQ"
real technical stuff is available from Siggraph

Quote:>Does this system work the same for outdoor terrain oriented scenes such
>as those in tribes?

In a word?
nope :)
Or, rather..
yes...

but more to the point...
It depends on who rights it.

Terrain engines are the most difficult to maintain speed with.

Quote:>Also I would like some info on collision bounding within a game map, ie:
>cant walk through pillars, you walk upward when going up a slope,

[snip]

It depends on how accurate it needs to be,
but you need to look at bounding sphers and boxes
and then geometry and ray intersections.

Quote:>And lastly, what order is best for a rendering pipeline ? I would think
>drawing the level first, applying all lightmaps, textures, etc, then
>drawing all objects and players, casting shadows, and last any fancy
>atmospheric effects.

What, you want me to tell you how I am righting my 3D Engine?
bwahahaha :)

Nice try *g*

I recommend you get Introduction to Computer Graphics by Fole, Veiner and
Van Dam
(excuse me if the names are hmm  innacurate) and then chase
the CGJ and Siggraph journals on the specific topics.

3D Engines sell from abour $300 to about $300,000+...
It's hard graft and can take years to develop.

I am in a position where my engines requirements aren't massive,
off the back of one project I an then fund the next and so on and so forth..

You say you just need to tie it all together?
I think you need to sit and do a lot of reading
and try implementing some dummy apps or test/learning apps
before you start tying it together.

Unless your going to build one of these $300,000 engines,
which is not likley to happen for about 3 years I'm sorry to say,
then your engine is likely to be tied quite strictly to how your game/app
needs to display your world/scene(s).

My current project is a terrain game, but at this stage it's an experiment
until I know performance levels will be good on most standard systems.

There are a huge number of things for me to implement before I can view a
scene
that will actually render something like production quality.

You are going to find this out for yourself as well.

OpenGL has just 8 lights in the standard implementation,
so do you write your own geometry engine?
How will you manage collision detection without knowing the
vertex co-ordinates?

there are some gl calls called feedback calls that supply window
co-ordinates..
will you try and compute the x & y values from Z?  IF that is possible.

Don't believe you've got it all just to tie togther,
it sounds like you've not written a smote of code.

So, get reading, get writing, loose (scuse the language *g*)
shit loads of hair and finger nails...

and prepare for a long, long haul

Anyhow,
hope thats helped a little,

Kind Regards,

Ian

remove nospam- for direct replies

 
 
 

1. Lighting Tips & Tricks info needed

Hello. Does anybod know if there are any good books or web pages that go

into lighting a scene? The packages that I'm using is Alias Studio 8 and
3D Studio Max.. My models are looking good, but the lighting could be
better.

I'm pretty much rendering images of products and displays that would be
used to sell a design. I know the less lightsources there are the
better. I'm having some difficulty in placment or whether I should use
point or spot lights, etc.

Thanks,
Orlando

2. is anybody usin Accelstar II AGP with max ?

3. In need of some nifty Textures

4. PushButtons under SoXtExaminerViewer

5. Raytracing page -- Info and Tricks!

6. BMP->JPEG

7. 3d graphic solution list and maya tutorial

8. TOASTER FLYER TIPS, TRICK, AND HINTS FREE INFO.

9. 3D Capture Info Site - More Info Needed

10. VESA programming trick needed

11. NEED HELP FOR A MAGIC TRICK