Photorealism in Pro/Photorender and beyond January 26, 2007
Product photographs taken for marketing purposes are more than photographs: The product is polished and cleaned with great care and every reflection and shadow is painstakingly checked. To take real photographs you need a real product or at least very realistic mock-up. What if you could make the same advertising photos using only Pro/E data and visualisation software?
That would mean the marketing photographs could be done even before the first prototype is manufactured. In visualisation software a virtual photo studio can be set up and Pro/E model brought in. This way there is no need to schedule new studio shooting session when the product changes. The images can be updated quickly because the same virtual studio is still there in hard drive just waiting to be used.
Recent Hollywood blockbusters have much more computer generated images than you might know. The same software used in movies can be used to create very realistic visualisations of Pro/E parts and assemblies. Quite often it is possible to make images that are indistinguishable from real photographs. Performance of PCs is increasing rapidly and the same time image creation software is getting better and better. This means that photorealistic images are becoming all the time more accessible for product marketing and design. We have the 3D product data already, now we just have to use it.
Pro/Photorender is the basic rendering software that comes bundled with Pro/E. It’s well suited for creating quickly images that are more realistic than the default OpenGL smooth shading. One of it’s strong points is that it’s integrated in the working environment, so no data needs to be transfered to another application. Pro/Photorender is also quite simple to use. On the negative side is the fact that it’s ability to mimic reality is rather limited, if compared to full animation packages.
In this article I will give you some instructions for creating better images for meetings and other presentations using Pro/Photorender, even if you are not a professional photographer. For those who need greater realism there are video production houses and ad agencies that provide visualisation services. In the second half of this article I’ll tell you what you should know if you want to hire an animation house or ad agency to do the visualisation for you.
Taking the most out of Pro/Photorender
I will not cover here the basic usage of the Pro/Photorender. The Pro/E manual covers these things somewhat and experimenting with the software helps even more.
Figure 1 shows a very basic rendered view of a plastic part. This is our reference image in this article. Now let’s see how we could improve the image.
Figure 1
Have a purpose
The first thing to do is to stop and think a moment about what purpose of the image should serve. You should have a clear idea of what you want to show. This will help you focus your attention to right details. It might also be useful to set yourself a time limit because it’s very easy to spend hours perfecting an image that is really used only in weekly meeting of your department . In our example image the purpose is simply to show the part design.
Set the staging
Now that you know what you want to achieve with the image you can start thinking how are you going to do that. Here are some things to help you get started:
Is one image enough? It’s not a good idea to fill one image with details. This makes images confusing. If the part (or assembly) you are visualising is very complex it might be good idea to show several close-up details in addition to the general view. Also, if you want to show function (movement) rather than form you could have sequence of images. With one image you can never show all the features of the object, so in our example I would really make two images taken from different sides of the part.
Show silhouette. The shape of an object is seen strongly on the silhouette edge surrounding the object. Rotate the object so that the silhouette shows the main shapes of the part.
Use some perspective. Perspective will give the viewer more visual hints about the shape than orthogonal view does. However, too strong perpective may be confusing.
Select Background. Background should be simple, so it will not take attention from the subject.
Figure 2 is the reference image after the above mentioned notes are considered.
Figure 2
Light the scene
Without light there is only blackness and without shadows there is only whiteness. To show the shape of an object you need to have different amounts of light hitting on different surfaces. In Pro/Photorender you can activate shadows using SelfShadows option in Render Configuration dialog. Self shadowing means that parts can cast shadows upon itself and upon other parts. Try some images with and without shadows to see which one you like better. Even without true shadows you get impression of light position and see shape of the object because surfaces reflect different amounts of light depending on the angle between surface and light.
The default lights in Pro/E are the Direction light, which is directed forward from camera, and the Ambient light, which is just a constant light level added everywhere. Turn off both lights. We will be adding a simple studio lighting setup that is much better suited for realistic images.
The first light to be added is the key light. This light should make shapes visible by creating light and dark regions on the part. Color of the key light can be pure white or slightly tinted to orange or yellow. Adjust the longitude and latitude sliders until you see the shape of the part clearly.
Light type can be point, directional or spot light. Point light casts evenly light to all directions drom a single point like a light bulb. You can adjust both distance from object and direction. Directional light is like Sun: All light rays travel to same direction. Spot light is like point light, but spot angle can be adjusted. You can set spot angle to 5 degrees to the effect. Directional and point lights are slower to render and have sharper shadows than spot lights if you use self shadowing.
The next light is the fill light. This light fills the black regions and it should be positioned on the other side of the camera than the key light (if key is on the right the fill should be on the left). Color of the fill light should be dark grey with maybe a slight tint of blue added. Adjust the brightness of the fill light so it wont burn the image white, but will lighten the shadows.
The last light to be added is the rim light. This light should give some highlights on the edges of the part. The rim light is located almost behind the part. Color of the rim light could be white or something very saturated. Same colors as seen in background might also work well.
Figure 3 shows again the reference image. At this image a basic three light studio lighting is used.Also, see the Figure 4 which shows the used lighting setup and light colors.
Figure 3
Figure 4
Assign materials
Material defines how a surface reacts to light. The surface could be shiny or dull, white or textured. A good way to see how the material behaves is to look at a real world sample (painted sheet, metal ball,…) and try to see any lights (ceiling light, window) reflected through the surface. Is the reflection sharp and well defined or blurry? Is the object transparent?
When you can see the nature of the material you can start to imitate it in Appearances editor.
When light hits an object it reflects the light back and some this light finds it’s way to camera. That light makes the object visible. In Pro/Photorender a material can reflect light with three different ways: Ambient, Diffuse and Highlight reflection.
In real world where we (most of us, anyway) exist there is lots of light bouncing from surface to surface. Some of this light is so well spread all over that it gives all surfaces almost constant light contribution. This is said to be ambient light. In Pro/Photorender it’s controlled by ambient light type. When lighting the scene we turned off this light because we are imitating a studio light setup where there is almost no extra light bouncing around. This means that the Ambient slider in material properties has also no effect. You can leave it to default value or set it to zero. In Pro/Photorender ambient light is calculated by adding a constant color everywhere and this can make images look washed out.
Some of the light that hits an object is reflected back evenly to every direction. A perfectly matte surface reacts this way. The brightness of surface depends on the angle between surface normal and incoming light beam. Drag the Shininess and Intensity slider to zero. You should see a surface that is perfectly matte. You can now adjust the surface color and brightness using the color picker.
The third way Pro/Photorender reacts to light is the hightlight reflection. Set Diffuse and Ambient to zero and Intensity to and Shininess to 100. What you see now should look like black shiny plastic. The white spot can be interpreted as a reflection of a light bulb seen trough the surface. If you now drag the Shininess slider slowly to zero you can see the reflection getting larger and the surface duller at the same time. Set the Shininess to 5 and Diffuse to 20. Now you should see material that looks like graphite. Drag Diffuse to 50 and you get brushed aluminium.
Pro/Photorender has also Advanced settings that are visible only when rendered. Unfortunately the Reflection and Transparency are handled in Pro/Photorender with very simple algorithm. I welcome you to try these effects, but sometimes these only make the model look less realistic.
Pro/Photorender also allows you to assign texture and bump map images to surface. Texture image is just what you would expect. It paints a texture image to surface. Bump map doesn’t directly paint color to surface. It rather modifies the surface normal according to texture brightness. This allows you to make for example dented surface look.
More info
Any basic photograhy book can helpful because mostly the same rules apply in digital and real world. Web is also good source for information. Just point your browser to your favourite search engine and start digging.
Beyond Photorender
I hope the previous section helps you to get better images, but if you need really photorealistic images you might want to consider hiring an outside facility to do the job for you. The other option is to invest to a higher end visualisation tool and spend some time learning to use the it.
Pro/Photorender is a working tool for simple visualisation work, but there are alternative tools for more demanding projects. Unfortunately most of these are not as simple to use as Pro/Photorender. It might not be realistic to expect people to master these packages without everyday use and deeper knowlegde about rendering and animation. There are however video production houses and ad agencies that provide animation and visualisation services. Here are some things to consider when preparing to start a project with outside production house:
Tansfering Pro/E data should be planned in advance and tested with simple models. There are 3D file format converters like Okino PolyTrans (http://www.okino.com) and Viewpoint Digital Interhange (http://www.viewpoint.com) that can read IGES, RENDER (.slp) and 3DPAINT (.obj) formats exported by Pro/E. Converting part files is straigthforward, but assemblies are more problematic and it may be necessary to rebuild the assemblies in visualisation application. This may be a large job if the visualised Pro/E assembly contains many parts. People at the production house have usually no knowlegde about structure of the visualised product, so time must be allocated for helping them to rebuild the assemblies.
It is very easy to refine the created images and animations, so use that to your advantage. It might be good idea to have two or three preview iterations before the images or animations are finally rendered in full resolution and image quality. In traditional photography shooting images again means that the product is set up in studio again and this can be very expensive. With computer generated images you can ask for changes even for the finished images. Of course, work is needed for the changes and rendering , but the overhead should be much lower than in traditional photography.
Examples
To end this article I would like present you some visualised examples.
Figure 5 shows comparison image of clear plastic part rendered in Pro/Photorender and in Lightwave (http://www.newtek.com). Lightwave uses more realistic shading model: Light bends when it goes through surfaces (refraction) and amount of reflection and refraction depends on angle between camera and surface. Lightwave also calculates self reflection where a part is seen in it’s own reflection.
Figure 5
Figure 6 shows our own product, a fuel powered radio controlled motorcycle (http://www.pumilio.fi). The image is rendered again with lightwave.
Figure 6
Figure 7 shows enclosure assembly we made for Ensto Control Oy (http://www.ensto.com). This image was used as a cover image for a 36 page brochure. All the 125 images in the brochure were rendered in Lightwave, althought using less fotorealistic format for clarity.
Figure 7
Copyrighted materials reprinted with permission from ConnectPress, Ltd. http://www.proe.com (This article was first published in “Pro/E the Magazine”. It was originally published in 2000, but after reviewing the material now in January 2007 I decided to publish it here as the information is still valid.)