Sampling tab

Anti-Aliasing

Min/Max Sample Rate

The minimum and maximum sample rate Turtle should use.

Turtle uses an adaptive sampling scheme that can perform both undersampling (less than one sample per pixel) and oversampling (multiple samples per pixel). A sampling rate from one sample per 256 pixels and up to 256 samples per pixel can be used.

The Min Sample Rate sets the initial resolution, where a negative value means a lower resolution than the original image (in powers of two). For example, -4 gives the original resolution divided by 16. The default rate is 1.

The Max Sample Rate sets the resolution of the final prepass, with 0 giving the same resolution as the original resolution. These controls should normally be left at default values -4/0, however you can lower them to render very fast GI preview renderings. The default rate is 2.

Contrast threshold

If the contrast differs less than this threshold Turtle will consider the sampling good enough.

Filter

Select from the filter kernels Box, Triangle, Cubic, Gauss (default), Catmull-Rom, Lanczos, Mitchell.

Filter Width

The width of the filter kernel in pixels. Range from 1.0 to 3.0. The default width is 3.

Filter Height

The height of the filter kernel in pixels. Range from 1.0 to 3.0. The default height is 3.

Advanced

Diagnose Sample Rate

Enable to diagnose the density of the sampling. For example, brighter pixels indicate more samples were taken at that position.

Clamp Values

To work efficiently, the sampling algorithm can clamp the intensity of the image to the [0..1] range. When rendering to OpenEXR. disable Clamp Values.

Min Value/Max Value

Sets the minimum and maximum sample rate. Turtle uses an adaptive sampling scheme that can perform both undersampling (less than one sample per pixel) and oversampling (multiple samples per pixel). A sampling rate from one sample per 256 pixels and up to 256 samples per pixel can be used.

Prepress

Min/Max Sample Rate

Min Sample Rate sets the initial resolution, where a negative value means a lower resolution than the original image (in powers of two). For example, -4 gives the original resolution divided by 16. Max Sample Rate sets the resolution of the final prepass. For example, 0 gives the same resolution as the original resolution. It is recommended that these options be left at the default values (-4/0), however decreasing them produces fast GI preview renderings.

Ray Tracing

Max Ray Depth

The maximum number of 'bounces' a ray can take before being truncated. A bounce can be a reflection or refraction.

Reflections

The maximum number of reflections a ray can take before being truncated. This limits the value set in each material.

Refractions

The maximum number of refractions a ray can take before being truncated. This limits the value set in each material.

Shadows

Controls at what depth a ray can spawn shadow rays. If set to 1, only primary rays will spawn shadow rays. If set to 2, the first bounce will spawn shadow rays as well. This limits the value set in each material.

GI Transparency

The maximum number of transparent surfaces a GI ray can go through, before being truncated. This is used by all gathering light integrators, like Final Gather and Monte Carlo.

Bias

An error threshold to avoid self intersections. For example, a shadow ray should not intersect the same triangle as the primary ray did, but because of limited numerical precision, this can happen. The bias value moves the intersection point to eliminate this problem. If set to zero this value is computed automatically depending on the scene size.

Related topics

• Texture Baking Settings window