Though Eevee is Blender’s standout engine in terms of speed and usability, many experienced Blender users still stand by Cycles as their preferred rendering engine. Unlike Eevee, Cycles is much more powerful especially when you’re looking for photo-realism in your renders. However, the more complex the scene or materials are, the longer you should expect the rendering time to be. It’s really important to know how to tweak Cycles’ settings to get the best and fastest renders possible. Keep reading to find out how you can easily speed up rendering in Cycles.
1.Enable GPU Rendering in Blender’s User Preferences
Once you’re comfortable with the basics of Blender and how it utilizes your workstation’s graphics card, this point may be overly simple, but for many first-time users, it may also be overlooked. The option to use your machine’s GPU and CUDA/OptiX is usually turned off when booting up Blender for the first time. Switching this on allows the system to know exactly which processing unit to commit the rendering operations to. Once you’ve done that, you will certainly see things in the viewport and rendering process smooth out.
In Preferences from the Edit tab, go to System. Then, under Cycles Render Devices, check CUDA or OptiX. Once complete, you should be able to have the option to switch the rendering device to the GPU back in the Render panel of the scene.
If you’re a Blender user with an AMD graphics card, the process may be a little different. CUDA and OptiX are exclusive to NVIDIA GPUs (GTX and RTX series, respectively) whereas AMD GPUs are supported by OpenCL. The same basic process to turn on GPU rendering applies, but you will check OpenCL instead of CUDA or OptiX. Also, keep in mind that GPU rendering is only available to users with AMD cards of GCN (Graphics Core Next) generation 2 or higher, so please check to make sure your machine’s internal setup is compatible before trying to use Blender with the GPU for rendering.
2.Decrease Light Bounces in the Render Tab
In regards to the scene itself, light bounces may be one of the biggest reasons for a slow render. You can learn more about ray tracing here, but simply put, light bounces are Blender’s way of simulating the natural properties of light and how it reacts, or bounces, on walls and other objects. It’s what helps the rendered scene look so realistic when compared to the viewport. The issue with realism is that it requires heavy rendering times.
This can be easily remedied by going into Cycles’ Render Properties panel and then into the Light Paths section. Turning down the Max Bounces total can quickly make rendering go much faster. The default setting is at 12, but usually somewhere between 4 and 8 will give you the same amount of realism without taxing the GPU come rendering time.
You can further fine tune the lighting setup by adjusting the individual light path types like Glossy or Diffuse, also found in the Light Paths section. Transmission shouldn’t be changed too much as it will decrease the realistic quality of the final render.
3.Decrease the Clamp Value Settings
Also found in the Light Paths tab under Max Bounces is the Clamp Value settings. Clamping sets the threshold for the maximum allowable amount of brightness and intensity in the scene. By reducing the amount, the render can finish much faster. This can also help with issues of random intense pixels of light, or “fireflies,” appearing in the render. Keep in mind that you shouldn’t mess around too much with the Clamp Value settings as doing so can reduce the scene’s realism.
4.Increase the Render Tile Size and Amount
During a typical render, you will notice that the image will begin processing in patches in the render viewport. Those patches of information are called tiles. Blender uses tiles to allow the CPU or GPU to focus on one specific piece of the image at a time, saving memory and reducing the chance of Blender crashing during the rendering process.
Blender now allows you to change the dimensions of these tiles. As some scenes render faster than others due to their resolution size, tiles are no longer based by count but by pixel size. Since the GPU is only able to render one tile at a time, the fewer tiles the GPU has to compute, the quicker the process will become.
In the Performance tab, also found in the Render Properties panel, you can change the tile size by X and Y dimensions. The default is set to 64×64, but 256×256 is the optimal tile size when using the GPU, drastically cutting down on the amount of time that the render will take. Conversely, when using the CPU to render, the best way to a faster render is to make the tile size smaller.
5.Decrease the Sample Amount
The most obvious, but most time-consuming aspect that needs to be addressed is the sampling count. Samples make up the noise that appears in the rendered image. The more samples you have, the clearer the final render.
In the Render Properties panel, you can define the number of samples in the Sampling tab using the Render and the Viewport values. The defaults are set to 128 and 32, respectively, but these won’t do if you’re looking for a final rendered image. Some professional renders may have a minimum of 3,000 samples. However, unless you are a purist of pixels, most people won’t notice if you process the render with a sample rate of 2,000.
If you are just rendering a still scene, this may not be much of an issue for you, but if you are rendering an animation, those samples will add up very quickly and significantly slow down the process. Experiment with sample rates and see how you can get the best image with the fewest samples. There’s no need to exhaust the GPU with processes that people won’t be able to notice.
Make Rendering in Blender Easy
Beyond Cycles, there are several ways to render your 3D models in Blender and it’s worth taking the time to explore what’s available. Be sure to read our articles on Blender rendering options and which rendering engine you should use if you want to upload your files to a cloud-based render farm like Render Pool. Happy Rendering!