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Tema: Professional Digital Studio Rendering with HDRI IBL and GI

  1. #1
    Administrador y fundador. Avatar de 3dpoder
    Fecha de ingreso
    Apr 2002

    Professional Digital Studio Rendering with HDRI IBL and GI

    Using Blender for Industrial Design CAD/CAM
    Claas Eicke Kuhnen

    A good image is worth a thousand words in Industrial design industry. Blender has become an essential tool for my work, because it allows me to visualize 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 possible to use it not only for product rendering, but also, to some degree, 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 to design, explore, and construct my objects. The Polygon tools, together with Subdivided Surfaces, allow me to model all shapes, which I would later be able to construct in metal with my hands. In silver smithing, most shapes are constructed out of sheets, 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 to model in blender.

    The recent addition to calculate the length and angle edges furthers my ability to account for correct measurements and dimensions. This is one of the most important advantages 3D modeling can provide you, because you have the possibility to 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 to be completely redrawn. (Screenshot: Measurements)

    In addition, not only does Blender allow to model mechanical elements, it alos makes it possible to animate them, allowing me to proof the concepts and troubleshoot possible 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, to 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 through them and then selectively shown to create clear and useful screenshots. (Screenshots: all Outlines)

    Part 2: Texturing
    The current versión of Blender and Yafray support most textures and surface light models that an artist needs to create pre-conceived material simulations. However specific materials like brushed metal or translucent materials are still either not yet possible or only possible with additional tricks and time. Specifically in my case, I am unable to acquire those anisotropic reflections and specular highlights, which are required to accurately simulate the fine-brushed surfaces with which I work. But to some degree this feel 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 renderings. However even a more coarse bump map already provides enough detail to simulate a brushed surface. The texture needs to be stretched along one axis and needs to have the right scale. (Screenshots: 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 to getting from using real studio lamps. Those lamps do not produce white light. The light is always a bit yellow. It was alos important to give the ground plane a different color than plain black. Those hue values were very minimal from pure blak but enough to create a natural look.

    Part 3: Rendering
    For my renderings, I have the expectation that the final result should be as realistic as possible. I use Yafray as the primary render engine, because it supplies me with HDRi lighting, Global Illumination, Color Bleeding, Caustics, and true Depth of Field. Specifically for my type of work renderings, 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 diffusion and colorization, which are sought in object studio photography. In my case, I 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 alos emit enough low key light to illuminate the metal work from all other directions. This eliminates any need for small light arrays to brighten up specific áreas, like the traditional three-key light setup.

    Furthermore, the GI option not only accounts for a proper shadow calculation and illumination of the whole geometry, but alos increases the realism of the rendering with calculating color bleeding and caustics. Many product renderings lak those fine details needed. Often, it is those fine details that will have a significant impact on the viewer with the realism felt while viewing the renderings.

    But just selecting an HDRi light map is not always everything you can do. In my situation, I only get light from one side. Because of aesthetic reasons, you want to eliminate of lighten the dark áreas so as to 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 to digital rendering with GI. The following two screenshots clearly show the difference. The GI calculates not only the light coming from the HDRi map, but alos calculates the light bounced bak by the light reflectors and this brightening up of the shadows on the cigarettes alos adds more detail to the metal reflections. As you alos can see, I use a chrome ball to find out where the light is coming from, that information enable me to 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, to bring attention to 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 aperture value of 0.1 to 0.5 is sufficient. To gain a smooth DoF rendering, in the render settings you need to disable auto AA. Depending on the scene you have to adjust the AA settings, in my scene I used 15 * 15 for AA Passes and AA Samples.

    For jewelry renderings, I 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 to select a too 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, too sharp reflections will only distract the viewer and steal attention away from the work.

    There are two possible ways to 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 way to create blurred reflections, though they are not physically correct. In this case, because the reflection should not get too much attention, this problem is not of any major significance.

    Clean one, Yafray
    Yafray itself supports the basic features of blurred reflections. Unfortunately, this feature is not accessible from within Blender interface. You need to 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 need to do is to enable the XML export, start to render, and stop Yafray the moment it is finished with loading the scene and starting to render(chek the terminal window for this during rendering). Open the XML file in any text editor and enter the following shader information 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" >
    <color r="0.5" g="0.5" b="0.5" />
    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 alos depends on the distance between your camera and the object. In close-ups higher values are needed.

    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 blok you want to be reflective.

    <shader type="blendershader" name="MAMaterial.002" >
    <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_cooktorr" />
    <hard value="50" />
    <environment value="env" />
    After this step, and saving the file, all you need to do is to let Yafray render the xml file. For my convenience I created a shortcut to Yafray.exe. I only drag and drop the xml file on the shortcut icon and the render process starts automatically.

    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 final render I let Yafray render the blurred reflections but I alos added a very fine stucci bump map to 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 to use the true blurred reflection within Yafray.

    You have to play a bit with the reflection values and the material properties because; every change for the reflections will alos alter the rendered color for the ground plane. At first the reflection and stucci map was too strong and distracting.
    In two steps did I lower the reflection value because this alos 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 to be taken seriously by artists who work in a semi CAD/CAM-like environment similar to the one that I work in and who need a well balanced set of modeling, animation, and rendering tools for the visualization. Because all my shapes are hand crafted, I do not need any tool which is required for rapid prototyping. Also, complex models can be imported from other applications to 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 seen as a proof 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 to keep in mind that both programs are currently undergoing a serious reconstruction. Blender is getting a new node-based material system and Yafray continues to improve the physical accuracy in rendering. As an artist, I hope that features already present in Yafray (such as blurred reflections) will be further integrated and more accessible from Blender. Those material and render options not only increase the potential of this software combination, but continue to close the gap between Open-Source and commercial software.


    Claas Eicke Kuhnen (aka F.ip2) Age 29

    I use blender for my general artwork, but mainly to visualize my silverworque to explore the design concept and proof interactions. I always try to archive fotorealism in my work and explore new technology and approaches.

    I worked during my undergraduate as a graphic and medía designer. Together with my brother we founded ConColori and provide industrial design solutions.

    Miniaturas adjuntadas Miniaturas adjuntadas Professional Digital Studio Rendering with HDRI IBL and GI-measurements.png   Professional Digital Studio Rendering with HDRI IBL and GI-outline_top.png   Professional Digital Studio Rendering with HDRI IBL and GI-outline_pers2.png   Professional Digital Studio Rendering with HDRI IBL and GI-outline_front.png  

    Professional Digital Studio Rendering with HDRI IBL and GI-stucci2.png   Professional Digital Studio Rendering with HDRI IBL and GI-texture.png   Professional Digital Studio Rendering with HDRI IBL and GI-pencere.jpg   Professional Digital Studio Rendering with HDRI IBL and GI-chromeball_test.png  

    Professional Digital Studio Rendering with HDRI IBL and GI-scene_topview.png   Professional Digital Studio Rendering with HDRI IBL and GI-scene_setup3d.png   Professional Digital Studio Rendering with HDRI IBL and GI-aa_setting.png   Professional Digital Studio Rendering with HDRI IBL and GI-dof_setup.png  

    Professional Digital Studio Rendering with HDRI IBL and GI-fakebumpreflection.png   Professional Digital Studio Rendering with HDRI IBL and GI-true_blurred_refl_nobump.png   Professional Digital Studio Rendering with HDRI IBL and GI-stucci1.png   Professional Digital Studio Rendering with HDRI IBL and GI-finale1.png  

    Professional Digital Studio Rendering with HDRI IBL and GI-finale2.png   Professional Digital Studio Rendering with HDRI IBL and GI-finale3.png  
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