Is there a way to reduce the number of polygons of a model (.obj or .3ds) without sacrificing the models detail? Is there a Mac program or utility that will do this?

in 3DS you could try to make a lower res model then render a normal bump map of the high-res model and apply it to the low-res model. Actually that's what I'm busy learning right now!

Rayraz describes the only method for poly reduction that I've heard of. It seems to be what video-game developers use for games on a poly budget.

Strictly speaking, it's not a bump map, it's a displacement map. Bump mapping is a pure optical illusion. Displacement map (or normal map) tells the rendering engine what to render, although the data are not present in the mesh itself. The difference between the two is best seen in a high-end program when you look the edges of a mesh, one with bump mapping and another with displacement. Bump-mapped mesh will have smooth contours, while the displacement-mapped one will look like it really has irregularites and stuff. Bryce cannot do displacement mapping. Bump mapping is only good up to a certain point, although it can go up to 999. (Which I'm convinced was an attempt at displacement mapping.) Still, even bump mapping can be good enough in most cases. Beside max and 3DS, you could try getting your hands on ZBrush, which can do wonders for the creation of good displacement maps on OBJs.

a displacement map and a normalmap are not the same though. A normalmap is a bumpmap with surface normals stored in it, but it doesn't actually really displace the surface, if you look at the edge of the surface, it's still not got the dents or extrusions you'll get from a displacementmap. However the added normal data allows for more real lighting of the bumped area's.

Sooooo, what are terrains in Bryce: bump, displacement or normal mapping ??? :P :D

Terrains in Bryce are the only displacement mapping there is. But because it has to be applied from a top view, and has no UV coordinates to wrap around a model, it will be no good for anything. The main problem is that the sides HAVE to be flat, because you're only seeing the top view. That's fine for some things, but not practical. Bryce's only bet would be a bump map.

Aye, when it comes to poly reduction, though, there are many ways to reduce polys. All of these methods will of course reduce the model's quality, although in many cases you won't be able to visibly see it. I use Rhino 3D for modeling. It allows full-on poly output control. When I'm exporting any curved surfaces, I use .obj files, as opposed to flat or angular surfaces which usually do fine in .3ds format. Either way, the meshing is the same in Rhino. I just don't trust Bryce's smoothing utility, so I stick to my modeler to do that kind of stuff... I generally leave spheres at 512 polys or so. The castle model you see at the link has a little over 200,000 polys (unoptimized, exported at the default .obj settings) with about another million polys in cylinders which make up the window gratings. If I optimized the model, I'm certain I could get the whole thing down around 250K polys, which means that I could probably load in 10 or 15 of these into on Bryce scene, and that's only with 512MB RAM... There are programs which will help you cut down your poly count, like PolyTrans, which is pretty much the industry standard for converting and adjusting files. Maya, for example, allows you to adjust your poly count on importing to whatever you want it to be, and shows you how much RAM the model is using up at any given time... If you have a specific model that needs adjusting, just email it to me (if it's small enough!) and I'll try to convert it for ya. And I'll try to dig up a free app that will help you with this. Maybe WINGS can do it?

Attached Link: http://www.blender.org/modules/documentation/htmlI/x3536.html

To give a straight answer to original question, which was not answered by any of us: there is not a way of reducing polygons in ANY application without loosing quality, it is phisically impossible, less polygons cannot describe the same surface as more. If you do modeling yourself, the best way to face this problem is to subdivide as needed, less subdivision (or polygon smoothing) for far away objects is necessary.

High end packages call this thing LOD (level of detail) and often they do subdivisions automaticly during render time :D

Message edited on: 04/07/2005 02:26

Yes, it's possible to reduce the number of polygons without loosing quality and in many cases the quality is improved. Many models have an unecessary number of polygons that are not needed and that render very baddly. It is common to happen with meshes created by 3dsMax, many of those extra and wrong polygons renders black in Poser. Rhino performs better tnan 3dsMax, but in the junctions of surfaces are created extra polygons too. I don't know any special software for this task, I do it by hand. There is a plugin for 3dsMax "polychop" that sometimes can be useful. The software for reducing the polygon number is called "decimator" so search with this name.

Lol, did you actually used Decimator ? :P

If you make a model with obsolete polygons like the ones kawecki is talking about then obviously you haven't really made a very clean model... My models I make in max never have a single bad polygon in them by the time I call them finished. I don't think this kind of polygons is really a fault of the application, it is a fault of the modeller using the application to perform incorrect modelling tasks.

I don't know if is people's fault or the software's fault not be a clean model. What I know is that most of downloaded 3ds meshes has this problem. I don't model with 3ds, Rhino has better results, but even with Rhino there is a lack of continuity between surfaces. You can increase the precision and this reduces the errors, but as result you have increased without any need the number of polygons and the errors still persist but are less visible. Is much better in a mesh of 400 faces to correct by hand 30 faces with a perfect mesh as result than to increase the precision and have a mesh of 2000 faces that looks good. The only decimator that I have used is the Polychop plugin for 3ds, is a free plugin and in some cases produce good results.

hmm... Well, I've never encountered corrupt polygons when modelling in 3dsmax unless it was by my own errors lol. Maybe you're referring to artefacts due to hard edges on low-res models? I just thought up another idea for lowering your mesh's resolution. You could select all the vertices in your model and tell your app to weld any vertices together that are closer to each other then a certain distance.

I discovered these errors when I imported the model into Poser and rendered. In the rendered images appear some parts that are black no matter the colour that I assign, in preview mode looks normal. I expand and extract the offending part of the mesh to found why is happening and the normal causes are: - Polygons with only two vertices. - Repeated vertices indexes in a face. - Duplicated faces. Poser handle very baddy these errors!

The whole point is that model cannot look better with less detail (polys) period. The fact that Decimator is used with 3D scanners was not mentioned earlier which is a key point with this software. When you have cloud point type of mesh data generated by 3D scanner, lot of errors are in it at the first place, and second ,way too many polygons are describing sufaces (milions and milions). So yep, mesh looks better when reducing it (sort of), but all those little bumps (details) scanned before are lost, you have to make them again while rendering with displacements and bump mapping. Decimator is not some kind of miracle software, DAZ Victoria 3 on closeup will not look better with oly 1/5 of the polygons then original, lol ! :P Of course, if rendering engine is doing subdivision (Bryce is not doing it, so you got what you got) it might be the same or close, but never better. When it comes to wrong constucted meshes, and bad polys, hey, like they said, it is NEVER software mistake, it does what we tell it to do !!! :) Black polys (in Poser) are usualy coused by inverted normals or 2 polys overlaping each other...:D

Aye, Kemal... To correct you, for once, read my post. I stated the obvious... And I agree with you 100%.

No problemos, LSD, it is obvious, indeed, forgive me for not stating it: I do agree with your post 100% too :D And BTW, Rhinoceros ROCKS !!! :P

Inverted normals don't render black in Poser, they render the same as ok normals, in preview mode are invisible faces. Duplicates faces can render black or with discontinuity depending on the normals. "When it comes to wrong constucted meshes, and bad polys, hey, like they said, it is NEVER software mistake, it does what we tell it to do !!! :)" How you can to tell the software to create a face with only two vertices or with duplicated indexes? Subdivision can do nothing with obj format, how you will be able to create correct new faces where there are not?, interpolating?, you only guess where can be and then there no need to subdivide, you can only interpolate the illumination as rendering engines does. It looks much more as Poser6 propaganda. Real subdivision is when the mesh is subdivided and the rendering engine choose the level of detail needed by the rendering. Subdivision is supported by Lightwave format.

Poser 4, does render darker(black) polygons with inverted normals (at least, mine does, oldie from MetaCreations) but it is OK if you think otherwise, lol :D To tell you the truth, I never had polygon created out of 2 vertices, since I started modeling, by modeler itself, looks like Poser might be interpolating numbers and rounding them up so it looks like it has only 2 of them...dunno. Since I subdivide and un-subdivide OBJ models almost every day for my needs i would think that it make some sence, otherwise I would not do it, assuming all this time that rendering engine is Bryce 5 which I exclusively work with :D

There are often duplicate polygons describign the same line or curve loosign soem of the duplcates will not actualy reduce the visial qualit of the mocel. Ex a cylinder it has 16 sides around and 1 in leangth another cylinder has 16 sides around and 4 in leangth. One has 4 times the polygosn of the other there is nto difference in the model otherwise. These kind of prolems happen often when you are exporting a spline made model. You set up subdivision and it works nice bit there are always places that really don't need subdivision. You have a lot more control if you use a polygonal modeler over the mesh but if you are modeling in a spline modeler you will come up with this problem. (exaple Hash, S-patch, Hama patch etc.)

• Polygons with only two vertices. - Repeated vertices indexes in a face. - Duplicated faces. There is no such thing as a polygon with only 2 vertices. By definition a polygon is a geometrical plane figure with three or more straight sides. In the very least, a three-sided polygon requires 3 vertices. The other 2 problems you speak of are a sign of poor modeling design and is the fault of the modeler not the tool. Getting back to reducing polygon count, there are several 3DS Max plug-ins and modifiers that can do that, some better than others. You can use the MultiRes modifier, or for better control use Polygon Cruncher. A low res model should have no extra or redundant polygons. Every polygon should have a reason to exist. If your model deforms when you eliminate one polygon, that polygon was serving a useful purpose and is needed to give form to the model. If you have an elongated rectangle that rectangle is low res when it contains only 6 polygons, one for each side and top and bottom. Anymore polygons would be wasteful and serve no purpose to the rectangle. By putting such a multi-polygonal rectangle through a polygon reducing program or plug-in will generally not lower its detail until taken to the extreme. In using such programs remember that they follow algorithms and it is difficult to say which polygons will be removed. Human intervention is best but slower for logical polygon reducing.

I normally only get 2 vertice polygons after welding points together in a mesh (I think) but then I delete them as being useless once I find them anyway. edit - so to answer chud's question.... whether you san reduce the polys or not (and maintai detail level) depends on your starting model. Sometimes you can get rid of some superfluous polygons, but more than likely you'll lose some fine detail if you try and cull too many polys. Bump maps and displacement maps are ways to give a surface the look of higher detail without needing lots of polygons to do it. Bryce doesn't do displacement maps unfortunately.

Message edited on: 04/08/2005 00:54

"There is no such thing as a polygon with only 2 vertices. By definition a polygon is a geometrical plane figure with three or more straight sides. In the very least, a three-sided polygon requires 3 vertices. " Of course that is not a polygon, it makes Poser very angry. They cannot be created by the modeler, so the fault is of the software. Exporting the faulty model and importing again Poser correct the problem, but many times removes a part of the mesh too!

Not the modeling softwares fault, modelers need to clean up their models. Many times while creating models they delete parts of it before getting it right and often that leaves stray, isolated vertices behind. When the modeler then exports the model, those stray vertices go with it. 3DS Max has a feature which will ask the user when he deletes objects if he wants to delete isolated vertices as well. Ive used 3DS Max since revision 3 in the DOS OS format and still do today, Poser since it first hit the market and Rhino since its Beta testing days. Poser is a very far cry from being a modeling program and can hardly compare, it just takes what you feed it. As the old saying goes; GIGO, garbage in, garbage out.