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Submitted by M.Knuth, posted on June 28, 2000




Image Description, by M.Knuth



This is an indoor screenshot of an engine Iīm programming with a friend. The editor / engine uses a pvs / sector based approach, using a bumpmapping algorithm able to use lightmaps with different lightdirections on an single pass multitexture graphics card :)

the engine self is an dll based modular constuct able to load / unload everything in runtime (you can even load other renders if you want)


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Archive Notice: This thread is old and no longer active. It is here for reference purposes. This thread was created on an older version of the flipcode forums, before the site closed in 2005. Please keep that in mind as you view this thread, as many of the topics and opinions may be outdated.
 
Betelgeuse

June 28, 2000, 12:05 PM

I haveta say this is pretty neat.

It's quite dark (I have to put my card on full gamma to see all the details). But still, cool! A nice break from terrain engines :) Lightmaps are pretty visible though, I dunno.

- Betelgeuse

 
Kurt Miller

June 28, 2000, 12:41 PM


Yeah, the screenshot is very dark, but when I brighten it up in my image viewer, it looks really cool. Nice work...

 
Johan Glysing

June 28, 2000, 02:55 PM

Low gamma? oh, my screen is pretty bright then... nice engine.
That lightmap looks a bit low detailed though (i always find something to complain on :-)

Have no one ever thought of using polygons for shadows... like in GoldenEye for the N64, and other Rare games. No need to use lightmap textures then. maybe its hard to calculate their positions?, i dunno, im no expert. :-)

 
Chris

June 28, 2000, 04:31 PM

Remember that N64 is running 320 x 240 and around 1000 polys per frame so there isnt alot of overhead to tracing the edges of the objects and drawing some extra polys. Free antialaising via blurry interlaced TV helps as well. On a high res PC game polygons as shadows are clearly visible in most cases. Many PC games do however use projected volumes for shadows. The coolest effect I think is a relatively new technique which renders shadow volumes to a texture at a small size then projects/combines it with the recieving surface so you get a nice smooth soft shadow thanks to texture filtering.

 
Elixir

June 28, 2000, 05:57 PM

On another note, because most (if not all) games use a Z-buffer, polygonal shadows will start "blinding", giving you Z errors. Sure, 32 bit Z-buffers fix this, but how many people run in 32 bit on average? ;)

 
Carl Warwick

June 28, 2000, 06:57 PM

It looks awesome, I see what the others are saying about the lightmap textures, but they don't look too bad.

Are you gonna get a website up with more screenshots, I'd love to see some other pictures.

 
Kezza

June 28, 2000, 09:04 PM

It is true that z-buffering is known to do irritating stuff like that, however
from my experience with opengl it is possibe to overcome that problem
as long as the polygons are on top of one another (not intersecting) by changing the
depthfunc to less-equal or equal and using polygon offset usually fixes things like that.

 
Alex Taylor

June 28, 2000, 10:23 PM

One technique commonly applied is to blur the lightmaps a bit after computing them, it gives a nice soft look to the lighting.

As for z-buffer errors, there are lots of ways to get around them. Were I'm working at the moment, we have to work with this old d3d retained mode piece of ****. On quite a few of the video cards we have here (and we have a fair variety), you get some horrible looking artifacts.

 
Alex Taylor

June 28, 2000, 10:26 PM

My point with the lightmaps was, they don't appear to be blurred and that may be why you think they're obvious.

 
M.Knuth

June 29, 2000, 07:59 AM

The lightmap rendering algorithm is only temporary. Finally I want to use a conetracing algorithm (not raytracing cones , but raytracing with cones ;) ) which is able to do antialiasing and soft shadows with no extra cost. (but it is still to slow to do it realtime)

Lateron Iīll amplify the picture by 2 (drawing a white quad over the screen with blendmode (DST_COLOR,SRC_COLOR) ), so it isnīt so dark

I have a "homepage" with screenshots and other stuff :
www.student.informatik.tu-darmstadt.de/~knuth
(be warned : itīs more like dos the html :) )

 
Prophylon

June 29, 2000, 04:22 PM

Could be me, but wont W buffers fix that problem?

 
Kurt Miller

June 29, 2000, 04:59 PM


[ignore this message, just fixing something w/the message board]

 
DirtyPunk

June 30, 2000, 12:23 AM

I nice method apart from Cone tracing you might wanna try is splatting. You take a 2d gaussian map, and splat it with the centre where the ray hits your polygon. The idea is, you use a bit of jittering to enhance the antialiasing effect. I do this, then combine with an extra filter down. It looks extremely good.

 
Arne Rosenfeldt

July 16, 2000, 06:28 AM

Hello

Is this done thisway?

inner_product(bumpdirection|lightdirection)*lightcolor*texturecolor

Arne

 
M.Knuth

July 20, 2000, 08:06 AM

No, this would not be possible on my voodoo ....

this bumpmapping algorithm uses several textures to compute the final one (so it need several passes of rendering, too)

it only works on dual-tmu graphicscards, which can handle two textures at the same time.

this method has some very nice advantage to "normal" bumpmapping:

- unlimited lightsorces
- fully opengl 1.2 compatible ;)
- moving lightsorces (via animated lightmaps)

and finally I can enhance it to "enviroment" bumpmapping

 
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