Texas Prairie: Glass by Alex Hogrefe

由专筑网小R编译

我一直在学习玻璃的图像制作，这是一种复杂的材料，在一定的照明条件下，它有很高的反射性，而有的时候又完全透明，因此，找到折射和反射之间的平衡点对于图像制作来说至关重要。

依据我制作的图像类型，在许多场景中，我都制作了玻璃，例如室内、室外、白天、晚上、阴天等等，但是，如果玻璃在画面中表达得非常重要，那么我就会把玻璃后面的内容制作出来，我一般喜欢在PS中重新制作玻璃，我说的重新制作并不是指加工渲染的图像，而是在渲染图像中并不会出现玻璃，然后在PS中把它当做独立的图层来制作，这样我就能够完全控制玻璃后侧的场景，以及玻璃的透明程度，那么这也意味着你需要很好地掌握玻璃的特性，并且平衡反射与透明度之间的关系。

针对德州草原办公楼的图像，玻璃后侧有很多内容，因此我通过渲染来制作，分别渲染了有玻璃和无玻璃的图像，在有玻璃的图像中，我应用了反射渲染元素，这样就能够把反射部分作为图层而进行后期的处理。

Illustrating glass is something I am constantly working on and studying. Glass is such a complex material in the sense that it can be highly reflective in some lighting situations and then completely transparent in other light situations. Finding the right balance of reflectivity and transparency is crucial for a cohesive and balanced image.
I have used many methods for illustrating glass in my images depending on the type of illustration I am creating: interior, exterior, daytime, night, overcast, bright, etc. However, in situations where the glass is prominent in the images, and I intend to extensively edit what is going on behind it, I like to rebuild the glass completely in Photoshop. What I mean by rebuild is that I do not work over rendered glass baked into the base files, but instead render the scene without glass and then bring it in as a layer or multiple layers in Photoshop. This gives me complete control over editing behind the glass, making selections, and the reflection on the glass itself. This also means that you need to have a good grasp of how glass will act in certain situations and adjust the reflection/transparency balance accordingly.
For the Texas Prairie Bridge illustration below, there was a lot of editing happening behind the glass, so I rebuilt it by rendering passes with the glass turned both on and off. I used the rendering passes with the glass turned off for my base images. I only used the reflection render element from the “Glass TURNED ON” rendering passes so that I could bring in that reflection as a layer.


1、建模渲染有玻璃和无玻璃的图像
1. Setup the Model to Render With and Without Glass


打开玻璃的基础渲染
Base Rendering with Glass On


关闭玻璃的基础渲染
Base Rendering with Glass off

如上所述，在打开玻璃和关闭玻璃的情况下我分别渲染了图像，然后在PS中，我应用没有玻璃的图像来作为基础图层，这样才能更好地制作玻璃背后的场景。

As mentioned aboved, I rendered two sets of base files with the glass turned both on and off. I then used the render passes with the glass turned “off” as the base images in Photoshop. The idea is that I will be editing the interiors behind the glass and I do not want to edit over the glass reflections.


2、编辑玻璃背后的图像
2. Edit Image Behind the Glass



不渲染玻璃意味着我可以应用材质ID来进行更加精准的选择，这样我就能够在玻璃后方加入植入和人物，调整室内空间。

Not rendering the glass means I can get nice crisp material ID’s to make precise selections so that I can drop in the background vegetation, insert people, and tone the interior spaces.


3、加入反射
3. Bring in the Reflections


来自“打开玻璃”通道的反射渲染元素
Reflection Render Element from the “Glass On” Pass


在PS文件的顶部图层添加反射部分
Reflections “Screened” On Top in the Photoshop File

玻璃后方的元素制作完成后，我就开始加入玻璃的反射，首先，我打开“材质ID”渲染元素，这来源于“打开玻璃”渲染通道，这样我就能够在场景中选择玻璃，然后在PS中新建蒙版来保存玻璃的设置，完成之后，我加入了“反射”渲染元素，并且把图层混合模式调整为“滤色”，这样玻璃的效果立刻就展现出来了，还可以通过复制图层和调整不透明度来优化反射的强度。

Once the elements behind the glass were in place, I began bringing in the glass reflections. I first opened the “Material ID” render element from the “Glass On” rendering pass so that I could select the glass in the scene and setup a mask over a group in Photoshop to hold the glass edits. Once the group was in place, I first brought in the “Reflection” render element and set the Layer Blend Mode to “Screen”. This instantly gives the images that glassy effect. You can duplicate the layer or adjust the opacity to refine how strong the reflection is.


5、玻璃的模糊
5. Glass Haze


模糊的制作
Painted in Haze


PS文件中的玻璃模糊效果
Glass Haze Turned on in the Photoshop File

在这张图中，我想要给会议室的连廊添加一些蓝色，但是如果要做到这一点，那么我也会在整体画面中加上一些蓝色，让它看起来有一些朦胧，模糊的元素也让玻璃的存在感更加强烈，如果觉得玻璃太过干净，我有时候就会这样处理。为了制造朦胧的效果，我应用了低透明度的软笔刷，慢慢地在玻璃上画一些白色。

One of the things I wanted to do in this illustration is amp up the conference room “Bridges” by giving them a blue tint. To do this though, I need to paint in some haze to give the blue color something to stick too. The haze also gives the glass more of a presence in the images which I do sometimes if the glass is feeling too transparent and clean. To create the haze, I just used a soft paint brush with very low opacity and slowing added white paint to the glass.


6、添加蓝色
6. Add the Blue


涂上蓝色
Blue Paint


蓝色部分图层混合模式为“叠加”
Blue Paint set to “Overlay”

最后，我用柔软的笔刷，在会议室连廊上添加一些蓝色，图层混合模式为“叠加”，这样玻璃就有了蓝色色调。

Finally, I used the soft paint brush and slowly layered on some blue paint to the bridges. I set the Layer Blend Mode to “Overlay” which gave the glass a blue tint.


7、最终成图
7. Final Image


最终成图
Final Image

我并不是只是渲染玻璃，因此我的图像都没有玻璃通道，但是在这样的情况下，我想完全控制玻璃后面的场景，那么这种方法就很好，相机后侧有一定的光线和外部几何图像，那么我会编辑反射，添加一些树木、人物，以及天空，这通过技巧就能完成，在之后的教程中我会着重解释。

I don’t always render a glass and no-glass pass for all of my images. However, in situations like this where I want to have full control of the glass and what is happening behind the glass, this method works best for me. For exterior images where there is lots of light and geometry going on behind the camera, I will actually edit the reflections to add trees, people, and sky textures. There are some tips to doing this successfully and perhaps I will revisit this in later posts.