Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!olivea!mintaka!bloom-beacon!eru!hagbard!sunic!liuida!isy!lysator.liu.se!zap From: zap@lysator.liu.se (Zap Andersson) Newsgroups: comp.graphics Subject: Re: Scene description: RayMond, comp.gfx's own scene description...:-) Keywords: Ray Scene Message-ID: <629@lysator.liu.se> Date: 13 May 91 12:05:47 GMT References: <625@lysator.liu.se> Sender: news@isy.liu.se (Lord of the News) Distribution: comp Organization: Lysator Computer Club, Linkoping University, Sweden Lines: 139 [Lot 'o blah blah of min deleted] >I think it extends creativity if the shading langauge is implemented. Sure >it is hard to implement, and most people out there won't take the time to >use/create whiz bang shaders. Too have the potential ability to do it in some >renderers will be worth it. >> >>Sorry for being incmprhnsibl, I'm under timestrain (bus in 1 minute ;-) >>and a stupid keyboard. >Hope you made your bus 8-) I did. And it was only th databus. I will need to take the adress bus today... >My point is this language can be really powerful if you want it to be. Another >important point is that it doesn't have to be. In the RIB description, to >instantiate a shader one does something like: >Surface "wood" "ringcolor" [.8 .8 0] >Now if my renderer reads RIB, but can't handle wood, it just sees the surface >description for wood and says ``opps, sorry user, I can't render wood'' and >ignores this description. Your renderer wouldn't have to care about the shading >language at all if it didn't want to. It could just use the primitives. Yeah, stupid of me, this works xactly th way I want it (DAMN KYBOARD MY 'E' is stupid) >An easy extension - if you see the shader above being instanced, and you know >how to do wood, just do wood, and ignore the shader description itself! What a >RenderMan compliant renderer would do is find the shader WOOD, bind it to the >primitive, and set up to interpret the shader description for the wood shader. >You don't have to though. To be RenderMan compliant you must provide the standard Yeah, rite. You are sooo right. >So to go through your list: >>Like I said in an earlier post: Let's define RayMond interface as: >>* Renderman primitives >RenderMan has these 8-) :-) >>* All features of renderman with things impossible in raytracing >> (e.g. true displacement shading) ripped out >Ignore them in your implementation. The displacement stuff is part of the >shading language, so if you ignore the shading language, you ignore the >displacement mapping. Yes, corrct, displacmnt shading is 'optional' >>* Effichiency shemes thrown in >This is part of the renderer. Some help in the interface may be a bonus, but >I don't know that it should be part of the standard. In a sense, the graphics >state can be used to realize a hierarchical structure in the objects. Since >things within a transformation block are likely related (since they are >transformed together) this can be used to get a tree structure on the objects >for those techniques that use such an algorithm. As a fundamental question, >I don't think that the modeler/renderer interface should specify how things >are grouped. It should be a job of the renderer to determine this hierarchy >based on the efficiency scheme that it uses. If it can't determine a good >hierarchy for an arbitrary scene, then it is probably not a terribly good >efficiency scheme (Now that I've said that, lets temper the remark with the >fact that this is an open research question in ray tracing. I don't think >any efficeincy scheme works best on all scene descriptions. The good ones >do well most of the time though 8-) AHA! NOW you ar on deeeep watrs my friend, a topic near and dear to my heart :-) hh heh heh :-) Like you said: No scheme is best for all images. Oftn, th bst way is to allow th modllr (i.e. the luser) to say: OK, this thing I want a grid around, do octr around these, and do bounding boxes hre, and zap-locked thermal tracing on those balls in the corner... >>* Editable objects (move, squach, fiddle) >Yeah, RenderMan is lacking in the transformation/deformation arena, but I >think that is a whole new ball game. Maybe we need another layer on top of >RenderMan that does these more complex operations for animation, and spits >out RIB code for each frame. Right again >>* Not nessecarily having standardized shading >Don't want it, ignore them! Or do your best with them. Or implement them. >Whatever! RIGHT AGAIN! >>CU all! >I just don't think we should start from scratch again, when all this work >has been done by Pixar to get a pretty good semi-standard out there already. >I just hope some kind soul out there will post a yacc grammar for RIB some >day to make it easy on everyone who wants to parse it. It should be pretty >simple to make the grammar, just tedious, cause there are lots of RIB >functions to parse, so there will be lots of rules.... Yah, this is in som sns what I wantd to say in my post, but due to bus stress and mor it ended up quite strang: What I wantd to say is: * Do rndrman as far as possibl * Don't nessasarily to rndrman shading (dont work too long on somhing that isn't ndd) DAMN KYBOARD! * Throw in schmes (Still think this - th only point you didn't convinc me! :-) >>* * * * * * * * * * * * * * * * * (This rent for space) >>* My signature is smaller than * Be warned! The letter 'Z' is Copyright 1991 >>* yours! - zap@lysator.liu.se * by Zap Inc. So are the colors Red, Green and >>* * * * * * * * * * * * * * * * * Greenish-yellow (Blue was taken by IBM) >It was smaller when there was only one signature 8-) Yeah, and it was smallr if th news softwar didn't includ it twiz... sigh >Later, > B >-- > Brian Corrie (bcorrie@csr.uvic.ca) >Under the most rigorously controlled conditions of pressure, temperature, >volume, humidity and other variables, the organism will do as it damn well >pleases. Sounds like some of the code I have written...... 8-) -- * * * * * * * * * * * * * * * * * (This rent for space) * My signature is smaller than * Be warned! The letter 'Z' is Copyright 1991 * yours! - zap@lysator.liu.se * by Zap Inc. So are the colors Red, Green and * * * * * * * * * * * * * * * * * Greenish-yellow (Blue was taken by IBM)