Wednesday, July 11, 2012

Balancing Rendering Quality and Rendering Speed.

A complex, high-resolution image takes time to render. Every 3D designer has to live with this in-escapable truth. But that doesn't mean you have to wait hours every time you want to render an image. Adapt your workflow to include faster, lower-resolution renders at intermediate stages of your design. This is a faster way to fine-tune your settings before you commit to larger, high-resolution render.

Here are a couple strategies for balancing quality and speed in your design process. 

Rendering Quality

When you first create a rendering with IRender nXt, we recommend that you start with a small rendering, 600px width, and just a few passes, start with 20. This will be enough for you to evaluate your lights, shadows, reflections and special effects without spending too much time watching a progress bar. When you are getting the results you want with a 20-pass render, increase the rendering size and add more passes.

Repeat the process until you're rendering at one-half your final size and one-half your final passes. When you're satisfied at this size you're ready to run the final.
Special Effects may require more rendering passes
Blurry reflection, like the lights in the wet concrete in this image, require more rendering passes. So, plan this into your workflow and know that additional time will be needed to evaluate design with special effects. See: Blurry Reflection for an example.
Rendering Quality vs Speed
Rendering quality is largely determined by two things:
  • Image resolution - how many pixels wide and tall
  • Number of passes - the number of times the rendering engine processes the image
Speed is the inverse of quality. Meaning the bigger the image and more passes you make, the longer it will take to render.

When you increase the rendering width from 640 pixels to 1,280 pixels, it will take 4 times longer to render - because there are 4 times as many pixels. If you double the size again - from 1,280 to 2,560 pixels if will take 4 times longer per pass again.
Similarly, if a 20 pass rendering takes 20 minutes, then a 700 pass rendering will that 700 minutes - or 12 hours. However, the higher the resolution, and the more passes you allow - the better the rendering quality.

Many of our users will use a workflow that includes several intermediatee renders then, they will let the final, high-resolution, high-pass rendering run overnight for the best quality. 

Rendering quality in the IRender nXt trial version

Some people notice the small rendering size, and limited passes which are the default settings for the Trial Version and are concerned that IRender nXt does can not create high quality renderings. This is not the case.
IRender nXt can produce renderings at any size and quality you desire. But to encourage an efficient rendering workflow, we set the defaults low so you can quick feedback on your designs. 

The balancing act. 
Whether your running the IRender nXt trial or rendering images for clients, you'll always be balancing quality and speed as your develop your final designs. But, if you plan a few smaller, intermediate renders into your workflow, you will learn how to create beautiful images in less and less time.