(photoshop)'HDRI from scratch tutorial'－－绘制HDRI photoshop, tutorial, scratch, HDRI, 绘制

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'HDRI from scratch tutorial'－－绘制HDRI

'HDRI from scratch tutorial'
by    seger van wijk
原文链接：http://www.3dtotal.com/team/Tutorials/hdri_from_scratch/hdri_01.asp

Introduction :  （简介)
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In this new tutorial, I will guide you into making a simple self-made HDRI from scratch, without the use of a photo camera. As you may know by now, an HDRI-image is the simulation of light in its natural state: as a high dynamic physics feature. Otherwise, simply Google HDRI and find all about the subject. The human eye is so fast in adapting to different light situations, and your monitor is actually so bad at representing the enormous space between the inside of your jeans back pocket at night and a bright day at the equator, that the fact that the sun is so powerful may strike you only after a day on the beach without a proper sun block. I guess the 32-bit room that we will use is still far from insufficient to capture the whole range between dark and light but it does do an extremely well job.
(在这个新的教程里，我将教导你如何在PS里制作一个简单的HDRI图像，而不是使用一张相机图片。正如你所知，一张HDRI图像是对自然环境光线的解算，这是一张高动态范围图像的特征。你可以简单的google一下HDRI，搜索所有这方面的主题。人的眼睛对不同环境的光线能非常迅速的适应，而你的显示器在表现夜晚你夹克口袋里的黑色背面与白天的地球赤道之间巨大的差异上却相当糟糕，这个事实导致你在没有合适遮阳伞的情况下，在沙滩上待一天会受到太阳很强的伤害。即便是我们将要使用的32位的图像空间依然不足以捕捉在黑和白之间的整个范围，但这已经足以很好的完成工作了。）
There’s a lot of HDRI photo material available from parties such as 'Sachform' and 'Dosch Design' that can be very useful in giving light and atmosphere to your 3D-scenery. But when your client wants a simple classic four-window reflection in his water drop, none of the beautiful things they sell, nor any of what you will find that is free to use, will do. Then of course, you do it yourself!
（商业上有很多HDRI的照片素材，比如Sachform' 和 'Dosch Design'，他们在给你的3维场景进行照明和烘托环境时是非常有用的。但是当你的客户希望有一个简单的经典的4格窗户反射在掉落的水滴上时，他们所销售的东西就没什么合适的了，而你也找不到任何可以免费使用的贴图。最后只能是自己DIY了。）
Apart of course from any major 3D package, you will need Photoshop CS2, in order to be able to merge a number (I will use 7) of “lighting situations” into a single radiance document. This radiance document will have a 32-bit range of dynamics, enough information to actually light your scene, throw shadow and make reflections without the use of specular shaders or channels. I won’t go into minute details of setting up the scene.
（请离开任何主流的3d软件包，你需要的是PS CS2，以便能够合并一系列（我将用7张）不同的照明状态图像到一个单一的图像文件中。这个图像文件将有32位的动态范围，能给你的场景提供足够的照明信息，投射阴影，制造反射而无需使用特殊的材质和通道。对于设置场景的过程我不打算阐述具体细节。）
The final render before we proceed: This image and the shadow are purely made with the HDRI that we will make ourselves without the use of a camera. For the sake of purity I haven’t edited the image afterwards:
（在我介绍前先看下最终的渲染图片：这张图片和阴影都仅仅由我们自己做的HDRI图产生，没有使用摄像机。为了保存最原始的效果，我没有对其进行任何后期处理。）

This is the render.（这是渲染的图片）

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HDRI from Scratch :  (绘制HDRI)
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The first thing that we do in Photoshop is making a simple pure white window in the middle of a 50% grey background Set it to 850x850 pixel and 16-bit colors and save it as 4.psd.
(我们将在PS中做的第一件事是在50％的中性灰背景中建立一个简单的纯正的窗户。设置图像大小为850×850像素，16位色彩，并将其存为4.psd。）


Next, introduce a Levels-channel to the background by clicking the channels-button and scrolling to levels. With the options that pops up you can alter the levels of the underlying pixels without making definitive changes.
(现在，通过点击调整层按钮，给背景添加一个色阶调整层,并打开色阶对话框。这样做的目的在于你可以将色阶应用到下面层的像素中，而不是破坏性的调整。）


Drag the black-value slider to the right until it is at level 42 or 43. When you slide, you will see the “wall” around the window update to a darker grey, while the windows stays pure white. Click OK and save this new document as 5.psd :
（向右拖动 黑色的滑动杆，直到值变为42或43。当你完成时，你将能看到窗户周围的墙变得更黑，而窗户仍然保持在全白。点击确认，将这个新得文件保存为5.psd）


Next, drag the slider to a position of 84 to 85 and save as 6.psd
（接着，继续拖动黑色滑竿到84至85得位置，并保存文件为6.psd）


What were actually doing is making illumination levels, just like a classical HDRI would contain.
(实际上我们做的就是制造光照梯度，就像经典得HDRI所包含的那样。）

The next settings for levels are slightly different. Move the left slider onward to 128, but also drag the maximum white level slider to about 180. This will dimm the bright white to a light grey, needed to cover the illumination of the HDRI completely. Like this:
（下一步的设置要使色阶变得更亮一点。移动左边的滑竿到180。

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Now, the wall and window look like the picture above. Save it as 7.psd. We now have the mid-illumination and three under exposed values (4.psd and 5, 6 and 7.psd). We just need three overexposed documents and we’re almost ready for a final detail. Set the right slider to respectively 212, 170 and 141 and save the results as 1.psd, 2.psd and 3.psd .
(现在，墙和窗户应该看起来像上面那张图片一样。将它保存为7.psd。我们现在有了中等亮度和低曝光度（4，5，6，7）的图像。我们现在需要3张高曝光度的文件，我们差不多已经准备好最终的细节了。设置右边的滑竿到（212，170，141）并依次保存到1.psd，2.psd，3.psd。）


To see if there is a logical order of grey values and document naming.
（看看你得到的是否是这样排列和命名的灰度图。）


Open all of them and add some lens blur. It’s not not an obligation but it looks nice in the final result. These are my settings
（打开所有文件，给他们添加一些镜头模糊。这不是必需的步骤，但能得到更好的效果，以下是我的设置。）


Next, go to File>Automate>Merge to HDR
（接着，进入文件》自动》合并为HDR。）


Browse to the folder you saved the exposures in and click OK. Photoshop will now batch-edit the seven exposures into an HDRI
（浏览到你保存文件的文件夹，点击确定。PS现在将自动将7张不同曝光度的图像合并到一张HDRI中。）

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When it is done, it will pop up an EV (exposure value) dialogue. Set the lightest Exposure to 3, the next one to 2, and so on to 1, 0, -1, -2 and -3.
（当你按照上述步骤进行时，会弹出曝光度的对话框。设置最亮的那张图片曝光度为3，接下来一张是2，依此类推设置为1，0，-1,-2,-3。）


When you’ve done it correctly, this is what Photoshop will come up with. You can uncheck the green ticks and view the results. Because we’ve been building a synthetic HDRI, the results from unchecking can be a little strange, but don’t mind: it will definitely work. Finally, click OK and Photoshop will build the HDRI for you, that you should save as a radiance document.
（当你正确无误的做了，PS应该呈现下图一样的状态。你可以检查绿色的记号，并察看结果。因为我们正在建立一张合成的HDRI，来于未经检验的结果也许有些陌生，但是别担心，它将工作的很好。最后单击确定，ps将为你生成HDRI，你应该将其保存为辐射文件。）


Next, load the HDRI in your 3D-app of choose. In Cinema 4D, the best place in a material would be the Luminance channel.
（下一步，在你的3d程序包中载入HDRI。在Cinema 4D中，最好将其放在材质的亮度通道中。）

As you can see, our simple window casts quite a lot of interesting reflections. This render is far from perfect and needs more that it has now but I wanted to keep it simple and plain. With the use of extra lights, the results could be improved but I’ve made my point: It’s possible to make your own HDRI from scratch. It goes without saying that you could draw anything that suits your needs.
（如你所见，我们简单的窗户制造了一些有趣的反射。这个渲染结果远远称不上完美，但我希望保持它的简洁和明了。通过使用额外的灯光，渲染结果能得到提升，但我已经达到我的目的：你可以自己绘制HDRI。不用多说，你可以自己合成适合你需要的任何东西。）

Happy rendering! （快乐的渲染!)


来源：译文3D网

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