Professional digital Studio rendering with hdri ibl and GI

[3dpoder]

using Blender for industrial design Cad/Cam
Clas Eicke Kuhnen.

A god image is worth a thousand words in industrial design industry. Blender has become an essential tool for my work, because it allows me todo visualice an idea with greater flexibility than any hand sketch, and thus visually commúnicates my design and concept. While Blender is not made for Cad/Cam and lacks Many features those packages frequently include, it is still posible todo use it not only for product rendering, but also, todo some degre, the whole design process.
part 1: modeling
As an object designer with a recent focus on metal smithing, Blender provides me with all the necessary modeling tools todo design, explore, and construct my objects. The polygon tools, together with subdivided surfaces, allow me todo model all shapes, which i would later be able todo construct in metal with my hands. In silver smithing, most shapes are constructed out of shets, wire, and tubing. Elements can be bent by hand or forged over shapes and then soldered together. This means that i mainly deal with geometric primitive shapes. And those are very easy todo model in Blender.

The recent addition todo calculate the length and angle Edges furthers my ability todo account for correct measurements and dimensions. This is one of the most important advantages 3d modeling can provide you, because you have the possibility todo work in correct proportions and dimensions. Small changes within the design or a change of the point of view can be achieved with a few mouse clicks and do not require the hand sketch todo be completely redrawn. (screenshot: measurements).


In addition, not only does Blender allow todo model Mechanical elements, it a los makes it posible todo animate them, allowing me todo prof the concepts and troubleshot posible problems.

In orthographic view, screenshots can be taken of the wire frame and composed together. Printed on paper they can be Cut out and glued onto the silver sheet, todo aid as guides for the shapes i saw in the metal. Working in layers aids a lot in this process because elements can be distributed th rouge them and then selectively shown todo create clear and useful screenshots. (screnshots: all outlines).




part 2: texturing
The current versión of Blender and Yafray support most textures and surface light models that an artista neds todo create pre-conceived material Simulations. However specific materiales like brushed metal or hola materiales are still either not yet posible or only posible with additional tricks and time. Specifically in my case, y am unable todo acquire those Anisotropic reflections and Specular highlights, which are required todo accurately simulate the fine-brushed surfaces with which i work. But todo some degre this fel can be achieved by using a procedural noise map or a Painted Bump map. The problem is that you can only reach a certain amount of detail before you Will run into moir patterns during render. However Even a more coarse Bump map already provides enough detail todo simulate a brushed surface. The texture neds todo be stretched along one axis and neds todo have the right scale. (screnshots: texture+testure2).


Alos a small color tint for the reflections and highlights Will reduce the sterile look of Raytraced reflections a lot and at the same time give the rendering a feeling which i am used todo getting from using real Studio lamps. Those lamps do not produce white light. The light is always a bit yellow. It was a los important todo give the Ground plane a diferent color than plain black. Those hue values were very minimal from pure black but enough todo create a natural look.
part 3: rendering
For my render, y have the expectation that the final result should be as realistic as posible. I use Yafray as the primary render engine, because it supplies me with HDRI lighting, global illumination, color bleding, Caustics, and true Depth of Field. Specifically for my type of work render, which Mimic the aesthetics of Studio shots, these features are essential in commúnicating what my work is about.


Hdri ibl can provide the proper natural light difusión and colorization, which are sought in object Studio photography. In my case, y use an HDRI file which contains only two light áreas, simulating the diffused light Walls. This Will produce extremely software shadows and reduce the amount of Burning highlights, this light probé supplies the desired amount of light from the proper direction in the scene, while eliminating any unwanted reflections (or Hot spots) on the work. The HDRI light map Will furthermore not only Illuminate the front view of the object, but a los emit enough Low key light todo Illuminate the metal work from all other directions. This eliminates any ned for small light arrays todo brighten up specific áreas, like the traditional thre-key light setup.


Furthermore, the GI option not only accounts for a proper shadow calculation and illumination of the whole geometry, but a los increases the realism of the rendering with calculating color bleding and Caustics. Many product render lak those fine details neded. Often, it is those fine details that Will have a significant impact on the viewer with the realism felt while viewing the render.

But just selecting an HDRI light map is not always everything you can do. In my situation, y only get light from one side. Because of aesthetic reasons, you want todo eliminate of lighten the dark áreas so as todo increase the overall dynamic range of the rendering. To brighten up shadows and dark áreas, white light reflectors are used in real life photography same trik applies todo digital rendering with GI. The following two screenshots clearly show the diference. The GI calculates not only the light coming from the HDRI map, but a los calculates the light bounced bak by the light reflectors and this brightening up of the shadows on the cigarettes a los adds more detail todo the metal reflections. As you a los can se, y use a Chrome ball todo find out where the light is coming from, that información enable me todo position the metal work correctly in the scene.


Rendering: Chrome ball_test.


Scene : topview.


Scene : setup3d.

Another very important tool for product shots is the Depth of Field. This effect is very useful, todo bring attention todo the specific elements of my work, while other elements are blurred. Yafray supports true Dof, which with higher sample values Will produce very Smooth results. The render time Will obviously increase with the amount of samples, but the end result is more than worth it. The Dof settings can be accessed from within Blender. An apertura value of 0.1 todo 0.5 is suficient. To gain a Smooth Dof rendering, in the render settings you ned todo disable auto a. Depending on the scene you have todo adjust the a settings, in my scene i used 15 * 15 for a passes and a samples.



For jewelry render, y prefer a textured Ground. One of my recent work is shot on a black, semi-reflective surface, which has a fine Grain texture. A common mistake made in simulating this effect is todo select a todo strong reflective value. The reflection on the picture Ground should only be slightly visible, so it accompanies the main object and prevents from appearing as a floating object. Additionally, todo Sharp reflections Will only distract the viewer and steal attention away from the work.

There are two posible ways todo achieve this result.
Dirty one, Blender internal:
The reflection can be diffused with a fine noise map in the normal channel. This is a quik bien todo create blurred reflections, though they are not physically correct. In this case, because the reflection should not get todo much attention, this problem is not of any major significance.


clean one, Yafray
Yafray itself supports the basic features of blurred reflections. Unfortunately, this característica is not accesible from within Blender interfaz. You ned todo manually edit the exported xml file and then render from Yafray. Furthermore Yafray does not shows blurred reflections in other reflections, which might be in some situations a limitation.


To export the scene into an xml file, all you ned todo do is todo enable the xml export, start todo render, and estop Yafray the momento it is finished with loading the scene and starting todo render(chek the terminal window for this during rendering). Open the xml file in any text editor and enter the following Shader información into your xml file.

First include the conetrace Shader at the beginning of your xml document After the <scene> tag.

<shader type=conetrace name=env reflect=on angle=10 samples=16 >
attributes>
color r=0.5 g=0.5 b=0.5 />
/attributes>
/shader>.

The sample value Will define how fine the blurred reflection is. Higher values above 10 produce the desired Smooth result in my scene, but this a los depends on the distance between your Camera and the object. In close-ups higher values are neded.
When you use the conetrace shader, you can disable the reflection properties inside Blender, in the next step you add <environment value=env /> inside the material Shader block you want todo be reflective.

<shader type=blendershader name=mamaterial.002 >
attributes>
color r=0.800000 g=0.800000 b=0.800000 />
specular_color r=1.000000 g=1.000000 b=1.000000 />
mirror_color r=1.000000 g=1.000000 b=1.000000 />
diffuse_reflect value=0.800000 />
specular_amount value=0.500000 />
alpha value=1.000000 />
emit value=0.000000 />
matmodes value=Traceable shadow />
diffuse_brdf value=Lambert />
specular_brdf value=blender_coktorr />
hard value=50 />
environment value=env />
/attributes>.

After this step, and saving the file, all you ned todo do is todo let Yafray render the xml file. For my convenience i created a shortcut todo Yafray, exe. I only drag and drop the xml file on the shortcut icon and the render process starts automátically.

But this Will result in two problems:
First with using a noise map you Will end up with having the noise pattern everywhere on the Ground plane. And the noise map does not create the desired surface texture i am looking for.


Second, when you only use blurred reflections rendered by Yafray you end up with a surface only showing the reflection but not structure.


In my FinalRender i let Yafray render the blurred reflections but i a los added a very fine stucci Bump map todo the normal channel of my Ground plane. This Will result in first a very nice blurred reflection rendered by Yafray and the stucci Bump map Will give the Ground plane the desired surface structure. This Will increase the render time a lot. In case you have a well working Bump map for the Ground plane, it might not be necessary todo use the true blurred reflection within Yafray.



You have todo play a bit with the reflection values and the material properties because, every change for the reflections Will a los alter the rendered color for the Ground plane. At first the reflection and stucci map was todo strong and distracting, in two steps did i lower the reflection value because this a los lowered the effect of the stucci Bump map.




conclusion :
While Blender lacks Many important modeling tools for Cad/Cam, this Project clearly shows the strength of Blender as a modeling and design tool and Yafray as a photorealistic render engine. Both are powerful enough todo be taken seriously by artists who work in a semi Cad/Cam-like environment similar todo the one that i work in and who ned a well balanced set of modeling, animation, and rendering tools for the visualization. Because all my shapes are hand crafted, y do not ned any tool which is required for rapid prototyping. Also, complex models can be imported from other applications todo be textured in Blender and then rendered in Yafray.

In terms of photorealistic output, Yafray already outperforms some of the industry solutions available as long as you use it right, this can be sen as a prof of concept that open-source software can realistically compete with commercial software solutions. While there are of course render and material features Blender and Yafray cannot support at the moment, it is important todo kep in mind that both programas are currently undergoing a serious reconstruction. Blender is getting a new node-based material system and Yafray continúes todo improve the Physical accuracy in rendering. As an artista, y hope that features already present in Yafray (such as blurred reflections) Will be further integrated and more accesible from Blender. Those material and render options not only increase the potential of this software combination, but continúe todo close the Gap between open-source and commercial software.

By.

Clas Eicke Kuhnen (aka f.ip2) age 29.

I use Blender for my general artwork, but mainly todo visualice my silverworque todo explore the design concept and prof interactions. I always try todo archive fotorealism in my work and explore new technology and approaches.

I worked during my undergraduate as a graphic and media designer. Together with my brother we founded concolori and provide industrial design solutions. Www.concolori, de.

Emails:
Fip2@gmx.net.

Claskuhnen@concolori, de.
www.blenderart.org.
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