Robicd wrote: > Well, I have to add that I import a lot of Wavefront .obj models into > Blender, they have one sided faces only, they are not autoconverted to > two-sided faces into Blender. Doing this, every object has one-sided > faces and Blender does the .ac exporting job very well. Why the hell > should I not have the opportunity to make just a few of those faces > double-sided and export them into a .ac file as they are? Sorry, but I > don't think that decision was _conscious_ as you say. >
It would be pretty easy to write a python script that would convert all faces in the scene to one-sided. I think you are also confusing two issues. The fact that objects are created by default with two sides is the work of the Blender developers. In the context of making computer animations, this is probably the right choice. The decision not to honor this data when exporting was made by Willian Germano, the developer of ac3d_export.py, so people wouldn't have to do a lot of work flipping them back. I also think that this was a correct decision, though perhaps offering both behaviors in the exporter would be better. Willian accepts patch submissions, so that is another possible solution to your problem. > Sorry Josh, I disagree with the above method; duplicating faces in order > to get double sided rendering into FGFS is not a solution to me at all. > That just increases the geometry and has bad consequences on > performance. I would not suggest this solution to anybody. Actually, this is not the case. There is a small performance hit on model loading because the extra data for that surface must be loaded. Once in memory however, it makes no difference. Plib converts 2 sided ac3d surfaces into duplicate 1 sided ones in memory and flips on set of normals for the simple reason that there is no such thing as a 2 sided poly in either openGL or a graphics card. This duplication also created a one time performance hit, but since the disk isn't involved it is smaller. From this point on both methods are equivalent. > By the way, FGFS does not resemble reality with high fidelity at all; > ok, it aims to that, but we are far from that. In the meanwhile, we > accept a lot of compromise between reality, performance and visual > quality into FGFS. Most 3d objects have to be seen from a distance and > do not need high poly geometry at all; zero thickness surfaces are very > often used and are a very good solution for building lowpoly objects > with double sided visible geometry. I guess I am not as willing as you are to make compromises. I really don't find rendering the edges of thin objects in scenery (so that they can be seen from all angles) to be a big deal. For a surface with N quads, this would usually work out to an additional sqrt(N) polys, which is not a hit at all. I have not found duplicating these surfaces to be much work at all, even in large 10,000 to 15,000 poly models and am happy with the benefits. Even in large models like that I have to deal with at most a few hundred polys in only a few objects. In addition, almost all of them demand duplication because they need to display some thickness, have different materials and UV-maps on each side, are also of subtly different shapes, or are transparent. In fact, I can't think of a single surface in the B-29 that I wasn't forced to create as two separate objects for one or more of those reasons. Also keep in mind that by exporting two-sided Blender polys you lose a lot of flexibility in UV-mapping. You will be stuck with the exact same UV-mapping on both sides of the object. I think you will also find that you will hamstring yourself when it comes to the ordering or objects, which is extremely important when using transparent materials and textures. > That is something Blender developers should face one day or another. > Blender is going to grow every day more, it has to cope with a wide > variety of modellers' needs; it has to be flexible with respect to that, > otherwise it will stop being used, even if it's free. I seriously doubt this. Don't forget that Blender isn't model building software, it's a computer animation package. It's a testament to how good the software is that people even use it at all for a purpose that it is not even meant for. Still, you are free to make models however you want. It's just that I have in the past made all the arguments that you are making right now, and I found that I had come to the wrong conclusions because of inexperience. Josh _______________________________________________ Flightgear-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-users
