While I am developing content for the Grandtour yacht visualization, I decided to bring up something that happened while I was rendering the Global 6000 project. The good thing about the internet when it comes to 3d models is its vast amount of 3d models libraries. Many of them come already prepared for rendering regarding the materials.
Lights, reflective and refractive materials are the ones that slow down the render mostly. When we do not pay attention, even more when we import objects we did not make ourselves, the materials can make the rendering phase take 250 minutes instead of its supposed 25 minutes.
In this case, what was delaying the rendering phase was the selected group of objects that I imported from a free source website. Even though it is a high quality model, it was mostly made of refractive materials. Also, most of the scene is made of reflective and refractive materials which slow down even more the rendering. I did not want to render it all over again since half of the image was already done, but lets just assume you really need this render, it is for a client and you are in a hurry.
Dividing Render Area
Instead of rendering the image all over again and because you can only apply squared regions to the render buffer in 3dsmax/vray, I divided the render in 3 areas. The number one I maintained and the other areas I rendered again. On the second area, I first removed the group of objects from the scene and rendered the area. Its presence was not that important since I used them mainly to fill the space.
Since the replacement renders have the same resolution as the original, they will fit exactly in its own place when on layers. The only thing left to do was to remove the dark area through the quick selection tool.
Take into account that rendering the same image twice with the same settings does not mean they will look exacly the same. Most of the time there are differences that go unnoticed as this one. The render that is going to cover the galley area came out slightly different colored. Still, it was a fast fix with the eraser tool and a low hardening percentage. We erase till it blends with the original.
So, we salvaged half of the original image and rendered the other 2 areas. The renders blending process on photoshop took me around 2 minutes. If I had chosen to render the whole thing again, it would take much more time.