Different implementations of truform in games

i wouldn't have expected anything less as the guys at Gray Matter are great artists. heck they made Kingpin on the Quake2 engine look damn near as good a Quake3.

 

No, we don't need a step backward.

We need a flexible form of programmable higher-order surfaces. Truform, if anything, is little more than a stopgap measure to show the potential benefits of higher-order surfaces.

One quick side note:
As for the ability to adjust normals to get a good image, this can't be done adequately for every model, and will affect vertex lighting, though I'm not sure if this is actually noticeable. The effects would be to increase the visibility of polygon edges if the normals are selected to be different for adjacent triangles, or just somewhat uneven lighting in other cases. But, again, not sure if you would notice this at all. As a side note, I believe every game out there uses the same model, Truform or no, so there's no way to tell if this is actually happening in the games. You'd need to be looking at the original art to tell.

 

I think the major problem with Truform is it's needed mostly in old games with low poly models. Unfortunately, those early games were made before Truform came out, so none of the models are "prepared" for it. So, what happens is you end up with a bunch of models that, while round, are just totally bloated. In the end, there's too much of a downside to the technology. You're better off just enabling AA and AF instead of Truform in an old game.

 

Kingpin is my favourite game, and the graphics are still pretty good, even for today.

 

i am sorry but i have to dissagree with you both Chalnoth and Nagorak. normals are adjusted for proper gouraud shading to achive a rounded look and truform simply takes that information and creates acutal curves though sub-divisions to enhance the effect. granted this does not work on models with hard edges but the simple solution there is just not to apply it to such models and many models are done compleatly with soft edges so it is not an issue there anyway. hence, as Dave implied and i also mentioned above; a good model is a good truform model. you do not have to make the model with trueform in mind for it to come out well, you just have to make a good model. rtcw is a great example as truform support was not added until a later patch.

ohh and just to show you that i am not talking out my ass (and a little self pimpage) i figure i should present an example of my own modeling efforts.

 

Actually I thought RTCW had a rather high polygon count for a game, much more then Quake3. In any case without TRUFORM complex models broke apart and look pretty bad at times as shown below. With TRUFORM the gross model distortions are smoothed over rather effectively.





Not to smooth, actually it is pretty distractive if you get close and watch this garbage, ahhhh with TRUFORM it doesn't happen nearly as much.

 

Normals are usually calculated as the average normal between the triangles that share the vertex. They are adjusted to fix the occasionally serious issues Truform has with many unadjusted models.

There are two primary problems with Truform. The first is the simple cubic interpolation. This cubic interpolation, by the way, is the same for the RT patches that the GeForce3/4 supported. The problem with cubic interpolation is that the patch size must be proportional to the "sharpness" of the surface. So, while it is possible to model rather sharp surfaces, you need to have small patches, which sort of defeats the whole purpose of higher-order surfaces.

The second problem is the fact that normals are used for the interpolation. Quite simply, when this is done, information is lost. That is, though the R200 and R300 may use the same interpolation as the GeForce3/4 cards, they cannot display every patch that can be made on the GF3/4 cards. You can look at this in two ways. One is from a simple data analysis standpoint. A triangular patch on a GF3/4 card will use a total of 9 vectors for the positions of the vertices and control points of the patch. A "Truformed" triangle on an R200 or R300 will make use of only 6 vectors. This basically means that the interpolation across each side is correlated to the interpolations across the neighboring sides.

Using normals for interpolation also means that the amount of work the artists must put into the models increases. I still contend that it would be more work to modify a model for Truform than for working with a HOS that is built directly into the design program. Of course, some models will obviously work fairly well without any special modification, but in games, those models aren't always common.

 

If RTCW's poly-counts were around the same as Q3, I'd have been worried. The Quake 3 models are around 800-1000 pollies max.

 

Chalnoth, you seem to have an somewhat of fundamental academic understanding of normals, but i find your comments way off in many regards. do you have any practical experience with 3d modeling? incase you didnt bother to follow the link i provided, i uploaded an example shot:




now i am just an amature but i think that is a good example of my experience when it comes to the topic at hand. the full undamaged model is ~1800 polys and the illusion of roundness created by the gouraud shading and glossmap is the result of a combination of standard calculated normals, projected normals and some hand tuned normals to top it off. this is done to achieve a good looking model regardless if truform will be applied to it or not. if care is taken simply to achieve the proper shading and gloss effects then truform can later be applied without issue. the simple fact is that nearly any model, designed properly with the intention of looking rounded, will take trufrom just fine.

 

nice model, kyleb

 

And yet every game that I've ever seen Truform screenshots of has had screenshots released that show the "wierd" results that Truform can cause.

As far as Truform is concerned, that car doesn't impress me at all. It has very smoothly-curved surfaces, and wouldn't have a very hard time working well at all.

Whichever way you slice it, Truform can have very serious visual problems. There are other technologies out there (at least on paper...don't know about hardware...) that can support much better surface interpolation.

Anyway, guess I was a little off on the lighting thing, but I just do not buy that Truform will "just work" for normals that are designed to work with, for example, a gloss map like that car uses. The nature of that car will certainly make it easy on Truform. Many other models are not so kind.

 

So you say that they choose this everywhere round car with Truform in mind because other types wouldn't look good with it?

 

Good example.
Look at the road at the upper right part of the picture.
Look how low poly it looks.
Now try to apply n-patches to that!

 

that you both for complementing my work Luke Philpot and K.I.L.E.R, it is always rewarding to have ones efforts acknowledged. also, i want to point out that the model was never made with truform support in mind, there is no truform in gta3 so it is not even an option. i imagine that if there was, it actualy would have an issue or two with it as i am am rather a newbie at modeling and i did fudge a bit on the normals, although i did my best to hide it. anyway, i was just presenting the picture to point out that i understand how normals work from practical application of them.


Chalnoth, the thing is, while it looks all curvy those curves are actualy about as light on polygons as i could make them and in game you can notice the sharp edges that it causes. even just from that pic you can see on the white car's right rear fender looks rather flat. i assure you that it looks much more round from other angles but i had to sacrifice some of that roundness to save on my poly limit. also i don't follow your "there can be issues so it is crap" mentality on this. if i applied that same mentality to other parts of my work i would have to throw all sorts of things right out the window. for instance dtxc, man that can make some textures look like crap, should we give that up as well Chalnoth?

also, most definitely Hyp-X, that would be a wonderful place to use n-patches.

 

The problem is with things that aren't intended to be round, getting rounded anyway. And, although I don't have any knowledge of 3D modeling, I have seen this exact problem firsthand. Don't get me wrong, Truform is a fine feature (but perhaps poorly named, given the occasional results), but personally I don't think it's that vital. Nor will I cry if support for it is dropped.

By the way, you can force Truform in the Radeon drivers.

 

You want a developer to not give users the option to mess with the tesselation levels but stick with one and only one level.

 

sure, but that would be improperly implemented truform; i could show you some textures that have problems with dtxc as well, i can show you things that look absolutely horid with dtxc actualy. also, how do you force truform in the drivers? in the control panel and ragetweak it is only off or application preference. is there some reg hack and if so can you set the value for a maximum angle for a soft edge as well? i take it it would be applied to absolutely everything at that point? that is bound to have issues but i would still like to try it out; so how do you do it anyway Nagorak?