如何制作HDR« make a HDR Image »
(引自The Lightbox) by Christian Bauer
Here you won't find a what a HDRI is, but how you can make one.
A little warning at the beginning: HDR-Images are not normal RGB- Images, they are build of different exposed photographies and that's why they can get real big. You also have to be very precise during the prozess of making a hdri to get a good result.
1. How to photograph
HDR-Images can be used as spherical enviroments but also as normal textures. You need lightwave to use them but the first new renderer are in betastage which will understand that format too.
What do i need?We want to make a spherical projection with only one viewpoint. For that we need a camera and a precisonspherical mirror. To photograph a sherical mirror have one very important advantage: You have the whole 360°/180° enviroment in only one Image (but you have also the camera on the mirror and a small area behind the sphere with distortions... who cares if you only need it for lighting a scene). For a HDRI we need at least five photos with different exposure time. We also need two statives, one for the camera and one for the spherical mirror.
The best way to photograph is with a digitalcamera, because you can be sure to get pixelprecise results ,while if you are scanning from a photo you also have to rotate the azimuth. Some Digitalcameras don't give you the chance to change the exposure time, but you can change the imagebrightnes and the camera stores the informations about exposuretime internally to your jpg-file. Well, photoshop or in this example ACDSee can read these information.
If you have a digicam where you can sett the exposuretime manualy don't forget the f-stop.
Here are the informations from a jpg, shot by a digicam
Exposure time 0,012.. F-number 4.4
The exposuretime have to be converted.
0,012 sec. are 1/77 sec. which is normally used for this Parameter.
So we have a exposuretime of 1/77 sec.
What have i do with the pictures now?I have taken someimages (shot freehanded) , i know the exposuretime and now i'm ready for photoshop:
We only have to crop the image:
Every image have to have the same height and width!!! The image have to be cropped along the tangents of the mirror.
nur zur erklärung, ich habe heute nachmitag beschlossen ein tutorial zu machen und hatte aber kein Stativ zuhause .. ;)
Your images should look like that now:
1/20 sec.
1/90 sec.
1/500 sec.
If you have written down the exposuretime you are ready for the funny part....
2. Software
We now have five images which have to be kompiled to a HDR-Image.For that we need a software from Paul Debevec .
This Software makes from many singleimages one HDR-Image. There is only one problem with this Software: it needs PPM-Images.
But there is a solution for the problem: when the JPE-Group released their imageformart they also gives away a encoder, and with this encoder also a decoder, which can convert any jpg to a ..yes, ppm. You can download it from here .... This is not my software, so i can't garantee you that this software is ok!!!!
to use the Software more easier i have put it in a RMB-command.
it's only hard for you if you don't understand german ;) ..i'm on a german w2k so i'm not sure if the things have that name i think.... please correct me!
At first we open w-explorere and go to the "Extras" menu, then to the Folderoptions and then to the Filetype-Tab.You can now see all registered filetypes. Now search for "JPG" ..and exactly jpg!.
Then the bottom should be names "advanced" or so... there you have a dialogbox where you press "new...". In the next dialogbox you can assign a command to the RMB-propertymenu which is similar to a batchfile.
We call the command "convert" and in the next field you have to browse to your djpeg.exe file and append the option "-ppm" and "%1"
"-ppm" converts the jpg to ppm , "%1" is the file whe have pointed at before.
If you now use the RMB over a jpg you can directly convert it to a ppm.. easy, isn't it?
There is another port of this software which can read tga's. You can download it from http://dcine.dyndns.org/mkhdr/and don't have to play with the software below.
Problem solved, so we can go on with Mkhdr.....
3. setup MkHDR
Mkhdr.exe is a Comandlinetool and need external options and something like a scenedescription. With the scenedescription you let mkhdr know what it should do with the files.
In this Textfile you have a list with your imagenames , exposuretime, f-Stop(?) and two options which are not important for the quality. The Textfile should look like that:
Wald_1000.ppm 1000 4.4 3 0 --->name of the image, 1000=exposure time(1/1000) ,4.4 = f-Stop, gain, neutral densityWald_50.ppm 500 4.4 3 0Wald_10.ppm 250 4.4 3 0Wald_10.ppm 125 4.4 3 0Wald_10.ppm 60 4.4 3 0Wald_10.ppm 30 4.4 3 0.....and so on
next we create a batchfile in the same folder as mkhdr.exeit should look like that:
mkhdr.exe -w dummy [path\]wald.txt wald.hdr
the parameter "-w dummy" is not required but without the parameter mkhdr crashes on my system......hmm.. ???followed by the textfile where [path\] is naturally the path to your textfile and then followed by the name of your outputfile.
RUN!
Ready!!!
郑欣淼院长
北京故宫博物院
电话：85117010
邮编：100009
郑院长：
最近从报刊杂志上获知有人倡议故宫博物院把位于故宫大殿旁边的星巴克咖啡连锁店撤出故宫，而故宫博物院也正在考虑该倡议。就此，我以一个普通年轻中国公民的身份向你及故宫博物院谈谈不同的看法，希望你们最终能打消这一与时代背道而驰的念头。
据一月二十二日的《参考消息》第八版的报道，倡议发起人，中央电视台的节目主持人芮成钢在他的博客上说星巴克的存在毁坏了紫禁城的庄严气氛，还说它不是全球化的表现，而是对中国文化的糟蹋。对此，我强烈抗议！他的观点非常狭隘，他的倡议也不能代表大多数中国人或大多数年轻一代中国人，更不能视为客观事实。
身为一个中国人，我们当然要维护我们固有的、积极的文化传统，但这不意味着我们要不加批判地维护我们的文化传统。紫禁城虽然是中华文明的象征之一，但紫禁城也是世界历史上典型的封建专制的象征之一。若是我们要去维护它的所谓“庄严气氛”，那我们是不是也有必要去维护“封建专制”呢？若是说在故宫博物院开设星巴克“不是全球化的表现”，那么把星巴克从故宫博物院撤走，就是全球化的表现吗？
事实上，全球化的表现之一，就是各种不同的文化和思想相互交流、乃至融合。无论是东方还是西方、无论是过去还是现在，包容的情怀和理念才能使一种文明、一个国家、一个民族赖以生存和发展。我们中国的近现代史已经证明了这一事实。过去，住在紫禁城的皇帝们拒绝了来自西方世界通商的要求，最终导致国家和人民陷入了灾难。我们应当深深吸取这一沉痛的教训。我的观点不是从拒绝经营西方商业就会导致某些不好结果的忧虑性出发，而是从我们中国人应该谦虚，应该懂得历史和看清世界发展潮流出发。况且在故宫开设星巴克咖啡连锁店，本身就是一件好事，这才能证明中国在变化、在发展，也有便于在明年奥运会期间为各国运动员和游客提供不同的、及时的饮食需求。
假如按照这位芮姓的观点，在故宫开星巴克是对“中国文化的糟蹋”，那么我们看到我们的国家领导人都穿着西服，甚至坐着西方国家生产的轿车，我们是不是也要求他们改穿“中山装”、并改坐“人工轿子”呢？我们是不是也要撤出那些采用西方的先进技术来测量和维修故宫博物院的专业人员和外籍人士呢？我们是不是干脆也把故宫里西方人发明的灯具全都改换成“蜡烛”呢？ 这样可能更正统哦！
最后，我建议贵院与星巴克公司就合同续签一事，达成谅解。如实在有社会压力，也可以找到一个喜闻乐见的新形式，包括保留星巴克的商标和产品品质，但辅助设施和员工服装都可以采用具有中国特设的模式，让很多年轻人都喜欢的星巴克咖啡继续在紫禁城内散发幽香！
此致 礼！
罗 正
二零零七年一月二十二日
（此信已于今晨通过邮局发往故宫博物院）
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No matter how powerful humankind thinks itself to be, the forces of nature have a way of asserting themselves, bringing with them both awe and terror. Fires、floods and earthquakes, the years are over and will never come back again--all provide starting images that remind us of the power of the natural world. By comparison, our own efforts of unflagging enthusiasm can seem puny: Uncle Sam and his close friends are desperately hanging Saddam with God's mission; Confucian's invisible hand which is still insidiously spreading his patriarchal virus with a kind smile veiled by dazzling economic feats cross Asia and becomes more emotionally volatile towards his brother in law -- Taiwan; Uncle Tom turns to fight with AIDS which has gruesomely spread to this sprawling world, instead of respecting to white people only. At this moment, a light show beyond the wildest dreams of human engineers makes us primeval once more, gazing to the heavens with same kind of wondering that the earliest of our kind must once have felt. If life is unique to Earth, man is absolutely the noblest animal that nature affords. Will man tame nature? Arguably, tame ourselves is the first step of taming nature. After all, man is a human being regardless of nationality as Socrates said he wasn’t an Athenian or a Greek but a citizen of the world. Happy New Year!
