Hints on Improving Rendering

I’m not a great renderer. I don’t have that artistic rendering eye, or a very developed sense of composition. I don’t really know all the options in the rendering packages very well. I recently did a bit of rendering to create my Gallery, and I learned a couple of things, so I thought I would pass those along to anyone who is interested. Any nice renders I’ve created have been the result of:

• a good model to start from
• a lot of luck
• ALWAYS use perspective
• the fact that if you experiment enough, eventually you will get something that isn’t terrible
• it never hurts to try to learn from experts

I believe that 70% of rendering is having a great model to start with. Naturally, I would try to make the outcome depend on a strength rather than a weakness.  To me, a great model for rendering is something with a lot of curvature. What separates good curvature from bad curvature could be an entire career all on its own, and I won’t go there this time.

One of the things that gets me is that a lot of rendering goofy-foots like me will try to make renderings without using perspective. One of the things that offends a non-CAD eye the most is the lack of perspective. CAD users have been trained to look at things without perspective because it is the best way to represent things on a technical drawing, but stuff looks funny without perspective.

Another thing you need to have is rounded corners. Sharp corners look bad in renderings. Even if you really intend a part to have sharp corners, put little fillets on them (unless you’re doing a knife or razor or something like that). Do one of your renders with and then without the fillets, and you will see. Rendering may take a little longer, and the model may take longer to rebuild, but we’re talking good quality stuff, not speed rendering.

Shadows are important. Personally, I like to avoid sharp shadows, and I like to avoid shadows that are low quality. Unfortunately, that combination means the rendering will take longer. The multi-core machines available today do renderings much more quickly, so that isn’t as much a concern as it used to be. There is a setting called “ambient occlusion”, which essentially means that a cavity inside the part that creates shadows on itself just from ambient light will actually make those shadows. My problem is that I can rarely find this setting. I did a few renderings a couple weeks ago that used the setting, but now I can’t find it again. Oh, well. Just be aware that its there somewhere, and if you find it, please let me know where it is.

Depth of field is another important and relatively easy thing to set up. Kim just got a nice Nikon D60 digital slrcamera for her birthday, and now she takes fantastic pictures. This is something that has always eluded me. I’m sure the rendering gene is related to the photography gene, and I have neither of them. Kim can select the part she wants in focus and make the rest of it kinda blurry. You can do the same thing in rendering, but you have to know the settings.

Depth of field and perspective can be set up using cameras in SolidWorks. Photoview has a separate setting for depth of field.

Background is important too. If you’re doing renderings for a blog like this one, rendering with a white background makes it best. If you’re rendering for a powerpoint presentation with a gradient background, rendering with a transparent background is best.

Materials are maybe the most important option in a rendering. If you have a curvy model, materials that are a little reflective are best. Curvature is hard to see unless the surface is reflective. If you have curvature and reflectivity, you also need something to reflect, so a background image is best. This is hard to set up in PhotoView, but in Photoworks, it is easier. If you’re material is not really reflective, a matte finish with some specularity might make the light do something interesting on the part.

This is why I say curvy models give the best renders. Flat surfaces don’t tend to reflect light in very interesting ways. I know, it’s hard to define interesting.

Remember that starting with SolidWorks 2008, SolidWorks is using the code word “appearances” to mean materials. Actually, appearances encompass materials, colors and textures, but I think the whole thing has become more rather than less confusing.

If you get in there and tinker with stuff, there are a lot of things to play with. I recommend playing using a small portion of the model, with the Render Area option on the PhotoWorks toolbar.

The things I like to play with the most are in the appearance propertymanager and in the Scene Editor dialog box. These two are where most of the action is.

Sometimes its hard to get the material and the background to play well together. Look at the towel rack image from earlier. On that one, I thought the material was too dark, but regardless of what I did with the material, I couldn’t get it to lighten up. The next thing to try might be using a different environment.

This is easier in Photoview than in Photoworks, but it’s not that difficult in either, really.

If a new environment doesn’t work to lighten up the part, the next thing might be to add a light. Lighting can be difficult to understand in PhotoWorks. In Photoview you don’t have much control over it, other than the background. Lighting in Photoworks comes from two sources. Environment and lights. In the environment, the light areas act like lights, just like in the real world, where surfaces reflect light. The second source is actual lights in the SolidWorks featuremanager. I usually try to leave the lights alone unless necessary. The rendering looks more natural if you use reflected rather than direct light.