Render Setup Dialog - Cycles Tab
Render Device - Controls whether the render will be done with the CPU or GPU.
Render Device Text Box - Selects which GPU(s) will perform the render (CUDA only). The "Devices..." button will display a list of available devices to choose from.
Preview Samples - The number of samples to render for material previews. Previews are the spheres that appear in the material editor and slate editor.
Samples - The number of samples per pixel to render. A higher value will produce an image with less noise, but will take longer to render. This option is the primary way you will control the speed/quality tradeoff for your render.
Clamp Direct - Direct sample clamp. This sets a maximum intensity that may be sampled for the first bounce of a ray.
Clamp Indirect - Indirect sample clamp. This sets a maximum intensity that may be sampled for bounces of a ray after the first bounce.
Random Seed - Sets the seed used to randomize noise patterns.
Animate Random Seed - When this option is selected, the random seed will automatically change every frame. Enabling this helps to avoid having very similar noise patterns in consecutive frames of an animation.
Step Size - Distance between sampled points in a volume shader. Lower values will be more accurate and take longer to render.
Max Steps - Maximum number of steps to sample in a volume before terminating.
Intensity Multiplier - Brightness multiplier for the environment map.
MIS Map Size - Sets the size of the MIS map to be used for the environment. Larger values will cause the scene to render with less noise from environment light at the expense of memory usage and speed.
Point Light Size - Point lights will be translated as spherical lights with this diameter.
Bitmap Width - Sets the default width of baked texmaps.
Bitmap Height - Sets the default height of baked texmaps.
Motion Blur Samples - Sets the number of samples to be used for deform-based motion blur. Note that the option does not affect object-transform-based blur or camera-transform-based blur.
Transparent Sky - When this option is enabled the alpha channel will be used to store transparency information for the render. By default the sky is considered transparent and all geometry is opaque.
Exposure - Exposure multiplier. This can be used to linearly brighten/darken the final render output.
Progressive Refine - When this option is enabled the renderer will sample each pixel once before moving on to the next sample. When it is disabled, the renderer will sample each tile to completion before moving to the next tile.
CPU Tile Size
Width - Tile width for CPU renders.
Height - Tile height for CPU renders.
GPU Tile Size
Width - Tile width for GPU renders.
Height - Tile height for GPU renders.