The Cycles Render engine can be very slow compared to Blender Internal; by the way, some of the rendering settings can be tweaked to make it work faster; the goal here is to avoid fireflies and noise, usually due to low samples and a light source that is too bright.
Rendered previews of an example scene, showing a cube on a plane with and without noise and fireflies
Start Blender and load the Gidiosaurus_playblast.blend file.
- Click on the Scene datablock button in the top main header to switch from BI to Cycles.
- Go to the Outliner and enable the visibility of the Light_key lamp in the viewport by clicking on the grayed eye icon.
- Put the mouse pointer inside the Camera view and press Shift + B to draw a box around the character's head, then zoom to it.
- Save the file as
Gidiosaurus_render.blendand press Shift + Z to start the Rendered preview.
If you have a capable graphic card supporting GPU (go to the last See also section for the link to a list of supported GPU graphic cards for Cycles), the next thing to do is:
- Call the User Preferences panel (Ctrl + Alt +U) and go to the System tab; on the bottom left there is the Compute Device item and the slot you can click on to select the device for the rendering: if you have a graphic card that supports this feature, set the GPU instead of the default CPU, and to make this permanent, click on the Save User Settings button, or press Ctrl + U, and close the panel.
- Go to the Render window under the main Properties panel and, in the top Render subpanel it is now possible to select the GPU item as a rendering device, but only if your graphic card supports CUDA.
This will boost your rendering speed several times, making it possible to significantly increase the rendering samples in the Sampling subpanel to reduce or even avoid the noise and keep good rendering times. Using the GPU, it's also possible to increase the size of the X and Y Tiles in the Performance subpanel (two or three times the default size is 64).
But, not everyone has a GPU graphic card yet, and there are also cases where you have to mandatorily use the CPU instead (for example, for very big scenes with a lot of geometry that doesn't fit inside the somewhat limited RAM of a graphic card).
In such cases, there are things you can do to try to obtain faster and better quality render results:
- Select the Light_key lamp and in the Node Editor window add a Light_Falloff node (Shift + A | Color | Light Falloff); connect its Linear output to the Strength input socket of the Emission node, set the Strength to 1000.000 and the Smooth value to 1.000.
- Click on the color box of the Emission node and change the color to R 0.800, G 0.800, B 0.650.
- Go to the Render window and in the Sampling subpanel set the Samples to 200 or a higher value both for Render and Preview, to reduce the noise as much as possible.
- Set the Clamp Direct and the Clamp Indirect values to 3.00 or 4.00 or even higher (they are set to 0.00 by default); when possible, it is better to leave the Clamp Direct item at 0.00 or use values higher then 2.00, otherwise you could get weird effects in the texturing.
- In the Light Path subpanel, disable both the Reflective Caustics and the Refractive Caustics items (unless you really need to have caustics in your render) and set the Filter Glossy value to 4.00 – 6.00.
- In some cases, it won't be possible to totally eliminate the noise or the fireflies; but, because we are going to render an animation, that is several frames in sequence, at least we can make the noise less noticeable and more natural looking: go back to the Sampling subpanel and click on the Seed slot to type
#frame. This creates an automated driver that takes the seed value from the current frame number, in order to have different noise at every frame.
The Light Falloff node for the Lamps, the Seed driver for the noise, the Caustics items and the Filter Glossy value
- http://www.blender.org/manual/render/cycles/reducing_noise.html
- http://www.blender.org/manual/render/cycles/settings/index.html
- http://www.blender.org/manual/render/cycles/gpu_rendering.html
- http://www.blender.org/manual/render/workflows/animations.html
- http://www.blender.org/manual/render/blender_render/performance.html
- A list of supported GPU graphic cards for Cycles can be found at https://developer.nvidia.com/cuda-gpus