Product Rendering
by Claas Eicke Kuhnen

As important as it is to explore design ideas quickly through modeling it is just as important to do the same with visual representations. In Industrial Design, the rendering aspect is treated as an additional service. It is not as important as the actual manufactured product. In addition there are alos opinions which state that good renderings are rather counter productive because the customer might bond with the rendered image instead of what the real product would be later.

This means that quik but good solutions are very welcome in Industrial Design. This is one reason why Hypershot is becoming very popular lately. I believe however, that with skill and experience, quality hand crafted renderings can be alos done quickly. Hour long renderings are not the best approach of choice in an environment in which time counts. And Blender has some nice "speed up" tricks. The biggest problem faced was to convince non-Blender users about the powerful render tools Blender has. Those include the material and compositor node system, render layers and passes, and of course the different render approaches reaching from simple lamp set ups to using radiosity and ambient occlusion. The goal is to reach decent results quick. This means well illuminated products - showing realistic material simulation - and additionally, photography elements like Depth of Field effects for enhanced realism. Blender comes with a rich set of light types including spot, sun, and área lamps, as well as ambient occlusion and vertex color based Radiosity. No MTL, Photon Mapping, Final Gathering, or Pathtracing is yet included, thus effects like caustics and local indirect illumination are quite difficult to generate in Blender depending on the scene. However with the current tool set we can achieve quite impressive results. Some are fast and easy to use and some are more labor intensive and take longer.

Highlight, mid tones, dark áreas and shadows are visual elements we can employ to give a flat rendering the illusion of 3d dimensionality. This means we can follow nature or simplify this and apply them in a rather graphical and illustrational way. This in other words means that we can do naturally looking images with even illumination or generate specific studies which focus on elements of the visualized product. That could be a highlight study or utilizing hard contrasts between highlight and shadow to emphasise the three dimensionality of the surface. For those steps we can select specific render types. Ambient Occlusion for example produces a more even, a more natural illumination while when using only few spot lights we can increase the light drama inside a rendering and focus on contours of the object.

Traditional lamp rigs first::
At the beginning of CG there was no Global Illumination of any kind. The artist needed to simulate direct and indirect illumination through placing numerous lamps to brighten up shadow áreas and color surfaces to faq color bleeding. Those so called lamp rigs were often very time consuming and complex to work with - simply because of the amount of lights you were dealing with. Two of those set-ups which mimic indirect illumination are still very common today.

1. SkyDome
You duplivert a lamp over half of a sphere and let the lamps illuminate the object in the center evenly - in a way similar to what ambient occlusion does. The skydome mimics the sky which emits light from all directions. The more lamps used the finer the result - in particular when shadows are employed as well. However,the the rendering will take longer also. In contrast to older versións, Blender now offers raytraced softshadows. We can use those instead of buffered shadow spot lights and get more realistic natural shadows. But again the more lamps - the more shadows - the longer the rendering. In studio photography hard shadows, are in most cases, not a desired result. Software lights are preferred because they enhance the perception of volumes. Hard shadows can be very distractive. In this case we could even ignore them. The trik with the skydome is to have a software illumination which alos mimics very light, software shadows or self-shadowing of an object.

To hide the lak of any shadow we could alos put our product on a perfectly reflective surface. When using duplifaces the base mesh for the dome is not being rendered by default and thus the background will be visible. The reflective ground plate will then only show the reflection of our desired product. This would reproduce a good studio environment.

Simple Skydome Setup:

  • Upper Half of one Icosphere / or Mesh of any shape
  • Spot light parented to Icosphere
  • Icosphere has "duplifaces" activated
  • Spot light's energy is reduced to a low value
  • Ground plate with shadow catcher (material/shaders/only shadow button) or surface with blurred reflections
  • World with blak background
  • Optional fill light to brighten up lower part of object

The skydome approach can be more refined.

To take natural color of the sky into consideration we can split the icosphere into two parts. Apply to each part a different lamp and give those two lamps different color and energy values. The sun side has more energy and more yellow, while the opposite side has less energy and is rather blueish to represent the light coming from the sky. With the sun like lamps having more energy, the possible shadows will be much stronger. When using raytraced shadows, it is advisable to use higher values for the shadow sample to produce softer looking results. However this can quickly increase the required rendertime as well. The light emitted from the sun being so far away can be treated as parallel light and thus could be use a single additional Sun light to cast the software shadow. It can alos be a spotlight. If your skydome is quite small, you might want to increase the size of the dome to alos illuminate the ground accordingly. If you use a shadow catcher as the surface, the product will be much easier to compose into any print media.

Rendering showing natural color illumination over reflective surface. An área light filler was used to brighten up the darker lower part. The lamp color is using a blend between sun color and sky color.

This trik can alos be used to simulate different light temperatures in a studio set. rotating the skydome and thus alos rotating the color emission you can decide where the sun would be in your scene. Along with this you need to move
the possible shadow casting lamp as well.

In addition the dome does not always have to be a sphere. It could be any kind of mesh type. With this the user has even more control on lights position and energy/color setup. This should enable you to quickly build a set of studio-like lighting setups for your future productions.

2. Seven Lamp Light Rigs:
This follows the similar approach to what the skydome tries to achieve. You use 6 lamps for a general global illumination. Left, right, front, back, top, and bottom. Those represent the six geographical directions we have. One lamp should be the sun lamp while the rest cover sky, horizon, and ground. Those lamps can be orientated strictly along a vertical horizontal path or depending on the sun's position be rotated.

Because only 6 lamps are used the amount of light energy used must be higher than with the skydome lamps. The result is again an even illuminated object with less lamps being used. (therefore saving rendering time) Spotlights or área lights can be used. Spotlights enable you to use buffered shadows which render quite fast. This will not only illuminate, but will alos provide natural shadows to the scene. However with only 6 lamps simulating natural shadows might be difficult. A seventh lamp can be used to place harder shadows and stronger illuminated áreas to focus attention to specific parts of the mesh. I would not use two accent lamps with shadows because that could start becoming rather distractive.

This setup is good for a fast light rig creation. playing with the lamp energy setting and color you can quickly simulate an in-door as well as out-door situation plus give the object the desired dimensional feeling. Because we only use 6 lights for the main tasque of lighting the scene, we can alos create harder contrasts compared to skydome. This is an aesthetic tool which can be quite handy. The seventh lamp can be used to significantly let one área or detail pop out of the image.

Simple Lamp Light Rig Setup:

  • 6 Lights coming from all 6 geographical directions facing the model
  • 1 or 2 additional accent lights for casting harder, more pronounced shadows
  • World with blak background
  • Optional: Ground plate with shadow catcher or surface with blurred reflections

As you can see the shadow is well pronounced - alos pay attention to the yellow color from the left and blue tones from the top. They are modeling nicely the contour of the tool. The lamp below the object functions as our light bouncer off of the ground - evenly illuminating the lower section as well.

3. Área Light Rig:

Area lights produce useful light emitting surfaces and thus alos produce the diffused light quality of a light box. With a few área lights we can quickly setup a well working studio utilizing light boxes commonly found in photography.

All that is needed is a left and right área light emitting the main amount of light. Here you can decide if you want to pronounce left and right evenly or if you want the left side to be more illuminated, which is, in my case, the situation. The top área light evenly illuminates the top contour while the ground light brightens up the lower part of the model. There is 4 smaller área lights which are moved very close to the model. Because the main área lights are rather left and right there is not much light coming from the front - the place were the camera man would be. We cannot use bouncing cards in Blender because it does not support Global Illumination this way. Thus we need a filler. That small light has the purpose of slightly brightening up the top part of the finger holder to prevent to dark áreas which might be alos visible though unpleasantly looking banding.

Simple Área Light Rig Setup:

  • 2 Lights left and right emitting most energy
  • 1 Light top putting emphasis on top contour
  • 1 Light below brightening up darker bottom part of model
  • 1 smaller Light filling front part - removing banding
  • 1 or 2 additional accent lights for casting harder, more pronounced shadows
  • World with blak background
  • Ground plate surface with blurred reflections

4. Simple Área Light Rig Setup with AAO:

  • 1 Light at a side emitting main energy
  • 1 Light top putting emphasis on top contour
  • AAO with a low energy value to brighten up scene evenly
  • World with blak background
  • Ground plate surface with blurred reflections

This setup only utilizes two accent área lights with a small amount of energy and a medium value for Appróximate Ambient Occlusion. AAO will function as the main illumination model to brighten up the scene evenly while the área light energy is being added to the model to put focus on the model curvature. AAO is our newest addition - the result is a grain free occlusion compared to it's raytraced counterpart and thus alos quite quicker compared to high sampled raytraced AO. However it behaves a little bit different. Depending on the mesh size you might get strong blotches of shadows. To control those you can make use of the "Distance" function to prevent them. This will scale down the shadow size between facing mesh parts.

Depending on where you place the área lights you can have more illuminated or more surfaces in shadow. The result with this rig has a little bit more dramatic contrast. Shadows in general are more pronounced. This is very visible in mesh parts which are close to each other.

5 Radiosity Solver:
Ambient occlusion has one major disadvantage - it works globally and not locally. It is great to be used in specific scenes where there is not a strong change in illumination like an outdoor scene. Another disadvantage is - in its current stage it does not support color bleeding. Blender actually has one tool that can do exactly that. The Radiosity Solver is a quite dusty tool in Blender - not too much used any more. It is a little cumbersome to use - however with some practice, quite excellent results can be achieved.

The way the solver works is by calculating emitted and reflected light and storing this in a texture, the so-called light map. This map is then used instead of lights to render the scene. Light is sent from meshes and not actual lamps. When you place a normal light inside a scene and its light rays touch an object, that light energy and color information
is being used with mesh surface shader information to onthe- fly render something illuminated and visible or in shadow and invisible.

This means no light - nothing visible. The light map works differently. Instead of calculating the illumination of the sphere during rendertime, the Radiosity Solver renders the scene and bakes that result onto the mesh. Upon rendering the scene, Blender does not have to shoot out rays to see what is illuminated or what not - it simply uses the light map texture and shows it. Thats all. The downside is that this technique is vertex based. The mesh will be subdivided during solving time to be fine enough to store the light map results with a desired quality. This means your mesh is getting messy. You have to apply a subsurface modifier before solving time. All meshes will be joined into one result. This means after the solving is finished, you have to separate your meshes again and remove materials added by this process. The biggest down side is that afterwards you cannot animate your objects because the light texture is static. Shadows will stay and not move with the object. However for still renderings this is not a problem. This technique is alos very nice to illuminate interior rooms when products are placed in it - very useful when your product has reflective surfaces. One of the nice parts is that the results are quite decent and once the solving is done, it does not have to be repeated again. Renderings are very fast. You can tweaque your textures and instantly render your scene. That is the main advantage of a baked GI solution. With the Radiosity Solver you can alos give meshes a light emitting value, custom building complete light shapes not possible with any other technique. As a bonus this technique alos calculates color bleeding in addition to bouncing. In my case I built a typical scene, a backdrop onto which the product is placed. Everything is inside a box. The box simulates a room for rendering, while at the same time functions as a bouncer for light rays. It is important that you have walls - otherwise emitted light will travel to infinity and you cannot achieve an indirect illumination. The front face of the box is removed to look into the room while it can be removed after solving time.

Technically speaquíng, the radiosity system is an illumination technique using no lights during render time. Lights are used only during solving time. This brings with it one small problem. Material effects like bump mapping interact with actual lights. This means using a bump map would be impossible with Radiosity. You simply will not see that texture.

However a workaround is similar to AAO using Radiosity as a global light solver while the accents are done with real lights. In my case I use área lights similar in size to the mesh lights for final rendering. The Radiosity makes everything nicely software, while lamps take care of the bump mapping and in addition add extra crispness to the rendering. Because of this situation did I use mesh lights with a low emitting value. Their outcome will be enhanced with the área lights. You could alos use stronger mesh light values and use only the specular of the área lights and not their diffuse. This way the área lights will only create the bump texture without any added light.

Radiosity Setup:
For Solving

  • 2 Key Mesh Lights at a side emitting main energy
  • 1 Top Mesh Light emphasis on top contour
  • World with blak background
  • Ground plate surface

For Rendering

  • 3 Área lights replacing the Mesh Lights
    World with blak background
    Ground plate surface with blurred reflections

Lets assume one rendering takes a lot of time or rendering an image múltiple times and comparing the results is not the most convenient approach. Blender offers a nice solution to this problem. Using the Compositor with Nodes, we can render the scene múltiple times. Each rendering would be a different lamp with the object. Those result can be mixed together in the compositor node. Through utilizing the "RGB Curve" we can turn each lamp on or off. With an input color, we could even color a lamp after rendering. All we need to do now is play with the curves until the desired result is achieved. This is a very quik and instant way to explore rendering. You can give all lamps the energy value of 1 - through the RGB Curve we can lower or increase the amount of energy afterwards. Alos simply give the lamp a white color since we can change that color with the use of an RGB input node. The RGB Curve can be used as a linear tool or similar.

Other nice utilities would be the Defocus node for Depth of Field and making use of render passes like a shadow, diffuse, specular pass and save those into separate image files. In Photoshop they can be modified elements added or removed and than composed together into a final rendering. Small problems in rendering are more efficiently removed in a paint program than redoing the rendering. Of course is it desirable to do good renderings in the first place. But sometimes you have to faq it. And isn't CG all about faquíng any way

by Claas Eicke Kuhnen