[教學]What is HDRI ?

[Cyber Oxygen]

As you might know each Pixel of a digitized Image normally is represented by three color-values known as RGB. RGB stands for Red, Green and Blue, the three base colors of the additive color space used by computers. With these three colors it is possible to mix any color within this colorspace. Each of these colors is represented by an integer number with
a range of 0-255. That means, it is possible to use 256 different brightnesses for each of these colors respectively for the Image. Image-formats based on this RGB range are known as LDRIs, Low Dynamic Ranges Images because they are bound to the 0-255 integer range.

Now, when you take a look at the real world, mother nature isn´t bound to a range when presenting it´s beauty to the human eye. There you have the darkness of a cave with almost no light (at least in the visible spectrum) but also the brightness of an object like the sun which is millions of times brighter than normal daylight, filtered through the atmosphere.

In 1985 Greg Ward invented the RGBE format to be able to work with real world ligthing in his rendering system RADIANCE. The RGBE format basically uses a 4th component known as the shared exponent (E). With the help of this exponent it was possible to describe the actuall brightness of a pixel in a real world brightness range (High Dynamic Range).

In the years after that invention there where developed several different formats to represent the real world brightness information inside of a digital picture. E.g. Bill Reeves of Pixar created a 33-bit long RGB format , Dan McCoy added it in 1996 to his free TIFF library (libtiff). Greg Ward later added the so called LogLuv format to this library which captures 5 orders of magnitude and the full visible gammut in 24 bits using a perceptual color encoding (There is also a 32-bit version f this format which s able to hold up to 38 orders of magnitude and often results in smaller files due to run-length encoding).

The HDR format of the pictures in this database uses the RGBE format explained above.

[h2o]

對於初學者可能會比較難理解...... 不如翻譯為中文吧!!

等我都准備下呢個topic 先.....

[Cyber Oxygen]

lighting 不是我強項
譯錯費時累大家

還是等你這個看更做la!!

[tdk]

this one is good

http://www.trinisica.com/sub_learn_type ... &issue=002

[Cyber Oxygen]

如果用maya來講
是不是得mentral ray 同埋 RAT 先支援hdri??

[h2o]

正路上系..... 不過唔靠呢d都可以扮到, 只要你明個理論就得, maya 有好多utilities 可以 plug

[heewing]

can anybody provide some 'interior' HDRI mapping, thank you!

[leelingzone]

對於初學者可能會比較難理解...... 不如翻譯為中文吧!!

等我都准備下呢個topic 先.....

h2o兄:
我知你就系做個呢類型cg(hdri)可否post一下教學黎教下我地的新丁呢?

[h2o]

剛剛轉左環境, 超級忙...... 遲d得閒一定會有新作同埋教學 post 上黎

[Joe kwan]

內文翻譯:

因為你可以知道，一幅數字化的圖像的每個象素通常被3 個稱為RGB的色值描述。 RGB支持紅，格林和藍色，計算機使用的附加的顏色空間3 基色。 由於這3 種顏色在這colorspace內混合任何顏色是可能的。 整數數目描述用這些顏色中的每個
0-255的范圍。 那表示，為這幅圖像分別把256 不同的亮度用於這些顏色中的每個是可能的。 基於這RGB范圍的圖像形式被稱為LDRIs，低的動態的區域圖象，因為他們被綁在0-255整數范圍上。

現下，當你看一下現實世界時，isn大自然厲害； 當提出它厲害時，被綁在范圍上的t； s美麗到人眼睛。 那裡你喝 黑暗洞與一起幾乎沒有光(在那些可見光譜內至少)但是也那些亮度的目標的喜歡比正常日光明亮數百萬時間的那些太陽， 濾過空氣。

在1985年葛列格．華德發明RGBE 形式能在他給予系統光輝過程中與現實世界ligthing合作。 RGBE 形式基本上使用第4個稱為被分享的解釋者的組成部分(E)。 在這個解釋者的幫助下描述在一現實世界亮度范圍(高的動態范圍)的一個象素的actuall亮度是可能的。

在在那項發明，在那裡那裡在發展幾不同的形式在一張數字化的圖內代表現實世界亮度訊息的地方之後歲月。 例如Pixar的比爾．裡夫建立33 位的長的RGB 形式，丹．麥科伊芳給他的自由爭論圖書館(libtiff)添加在1996年的它。 去圖書館這的形式ogLuv哪5項命令的大小和使用知覺編碼顏色的24 一點兒那些深濃可見gammut的捕獲物(f 版本32位這幾次形式

在這數據庫裡的圖的HDR 形式使用在上面解釋的RGBE 形式。
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

[fellini]

正!
你用咩software譯?

"去圖書館這的形式ogLuv哪5項命令的大小和使用知覺編碼顏色的24 一點兒那些深濃可見gammut的捕獲物"

笑死

[Joe kwan]

去圖書館這的形式ogLuv哪5項命令的大小和使用知覺編碼顏色的24 一點兒那些深濃可見gammut的捕獲物

唔明呀!

我用的是 Dr.eye

[Siegfried]

HDRI....a good stuff I've been looking for years in Flamingo but...

[8870]

支持

[sheng]

If anyone interesting in HDRI, maybe can take a look on this :
http://www.tutorialized.com/view/tutori ... -Ray/24519