3D Visualization: Glass Renders
Over the past several weeks, I’ve been experimenting with rendering glass materials in Cinema 4D. Below is an explanation of my process.
Materials
One of the things I learned was the simpler the scene, the better the result. Initially I played around with materials that had multiple attributes for glass; color channel, reflection, reflection color, transparency, bump maps, specular highlights, etc. Once I simplified the glass material and scene, it looked much more realistic. In the glass material, I turned off color, reflection, and specularity. I enabled the reflection channel only and turned up the index of refraction to a value of 1.52.
Environment
I kept the scene setup as simple as possible using one plane for the floor and one plane for the background. In most of the renders, the floor plane uses blurry reflections. In my first few glass scenes, an HDRI image was used to create realistic reflections in the glass. This method works well, but can be a bit much in certain situations.
Lighting
Once I started experimenting with the more advanced features of the lighting tools and deleted the HDRI setups, the scenes really started coming together and looked more realistic. Using area lights with reflection visibility enabled in the details tab allowed me to better control my highlights. Additionally, using the lighting tool and placing my specular highlights exactly where I wanted them helped as well.
Shadows
For most of my 3D visualization work, I enable shadows to help visually ground objects to the floor. For this series of glass renders, most of the scenes did not need shadows enabled. On the scenes with dark backgrounds, enabling shadows was pointless because they would not be seen in the final image. For scenes with lighter colored backgrounds and blurry floor reflections, shadows tended to clutter up the image. Turning off area shadows also decreases render time, that’s always a good thing.
Depth of Field
About half the renders shown here use a fake depth of field created in post-production with a variety of methods; gaussian, motion, or lens blurs. The images look more realistic when depth of field is enabled in the 3D environment but also take longer to render. To achieve more realistic depth of field inside Cinema 4D, I dragged the closest glass object into the camera’s ‘focus object’ field then enabled DOF in the physical render engine.
Rendering and Post-Production
For these 3D visualizations, I used Cinema 4D’s physical renderer with multi-pass layers. I also created an alpha channel for all the glass objects by using a compositing tag and adding an extra object buffer layer to the multi-pass render. For the post-production stage, again I tried to keep things as simple as possible. The first step was to delete any multi-pass layers that were not necessary to the final image. I then duplicated the reflection layer in Photoshop and added a bit of gaussian blur and turned down the opacity. This gives the highlights a subtle 'bloom'. To finish off these images, I created separate layers for sharpening and grain.
Enjoy.
