《HDRI图像技术的秘密书籍》The HDRI Handbook Rocky Nook

本书籍是关于HDRI图像技术的秘密书籍，大小：31.22 MB，PDF高清，共344页，语言：英语。人人素材整理发布。

HDRI是High-Dynamic Range （HDR） image的缩写，就是为了解决这个问题而发明出来的，简单说，HDRI是一种亮度范围非常广的图像，它比其它格式的图像有着更大亮度的数据贮存，而且它记录亮度的方式与传统的图片不同，不是用非线性的方式将亮度信息压缩到8bit或16bit的颜色空间内，而是用直接对应的方式记录亮度信息，它可以说记录了图片环境中的照明信息，因此我们可以使用这种图像来“照亮”场景。有很多HDRI文件是以全景图的形式提供的，我们也可以用它做环境背景来产生反射与折射。这里强调一下HDRI与全景图有本质的区别，全景图指的是包含了360度范围场景的普通图象，可以是JPG格式，BMP格式，TGA格式等等，属于Low-Dynamic Range Radiance Image，它并不带有光照信息。

HDRI拥有比普通RGB格式图像（仅8bit的亮度范围）更大的亮度范围。标准的RGB图像最大亮度是值是255/255/255，如果用这样的图像结合光能传递照明一个场景的话，即使是最亮的白色也不足以提供足够的照明来模拟真实世界中的情况，渲染结果看上去会平淡而缺乏对比，原因是这种图像文件将现实中的大范围的照明信息仅用一个8bit的RGB图像描述。 但是使用HDRI的话，相当于将太阳光的亮度值（比如6000%）加到光能传递计算以及反射的渲染中，得到的渲染结果也是非常真实和漂亮的。下面的两张渲染的图片可以看出使用HDRI后带来的巨大差异。

HDRI文件是一种文件，扩展名是hdr或tif格式，有足够的能力保存光照信息，但不一定是全景图。Dynamic Range（动态范围）是指一个场景的最亮和最暗部分之间的相对比值。一张HDR图片，它记录了远远超出256个级别的实际场景的亮度值，超出的部分在屏幕上是显示不出来的。可以这样想象：在photoshop里打开一张从室内往窗外外拍的图片，窗外的部分处在强烈的阳光下，曝光过度，呈现的是一片白色，没有多少细节。你将毫无办法，调暗只会把变成灰色而已，并不会呈现更多的细节。但如果同一场景是由hdr纪录的话，你减低曝光度，原来纯白的部分将会呈现更多的细节。

The HDRI Handbook Rocky Nook
High Dynamic Range Imaging for Photographers and CG Artists
Contributing Authors: Uwe Steinmüller, Dieter Bethke, Bernhard Vogl

The HDRI Handbook reveals the secrets behind High Dynamic Range Imaging (HDRI). This cutting-edge imaging technology is a method to digitally capture and edit all light in a scene. It represents a quantum leap in imaging technology, as revolutionary as the leap from Black & White to Color imaging. If you are serious about photography, you will renrencg.cn find that HDRI is the final step that places digital ahead of analog. The old problem of over- and underexposure in analog photography, which was never fully solved, is elegantly bypassed here. A huge variety of subjects can now be photographed for the first time ever.

HDRI emerged from the movie industry, and was once Hollywood’s best kept secret. It is now a mature technology available to everyone. The only problem was that it was poorly documented…until now. The HDRI Handbook is the manual that was missing.

Many questions remain open even for the hip CG artists that have been using HDRI for years. This is where The HDRI Handbook comes in. Included here is everything you need to build a comprehensive knowledge base that will enable you to become really creative with HDRI. This book is packed with practical hints and tips, software evaluations, workshops, and hands-on tutorials. A new breed of community driven HDR software is included on the companion DVD, so you can hit the ground running. Whether you are a photographer, CG artist, compositor, or cinematographer, this book is sure to enlighten you.

详细内容包括：
Topics include:
• Understanding the foundation of HDRI
• Tools for a High Dynamic Range Workflow
• How to capture HDR images: today and tomorrow
• Tone mapping for creating superior prints
• HDR Image processing and compositing
• Shooting and stitching HDR panoramas
• Image based lighting and CG rendering
• World premiere of Picturenaut and Smart IBL
• Creative uses and unconventional applications


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