MayaMan Help Contents

# MayaMan Scanline Options

This dialog contains options that are specific to renderers that support scanline rendering. These options apply to PRMan, and may or may not apply to other particular scanline renderers.

### General

#### Clamp to Alpha

When this option is on, all color values being output will be clamped to their alpha values. Shaders outputting color values greater than one can sometimes result in a color greater than the alpha, which can lead to compositing problems.

#### Binary Dicing

When this option is on, the renderer will only dice patches into grids of micropolygons of a size that is a power of two. This can be used to prevent cracking on patches with high curvature.

#### Extrapolate Derivatives

PRMan 10.0 and later has an attribute that extrapolates derivatives, sadly this option can cause render artifacts on rough or bumpy surfaces. PRMan defaults this value to on but mayaman defaults it to off as it generally causes more harm than good. Even though it's an attribute mayaman only provides a global setting.

#### Keep Creases

#### Disable Displacement

When enabled, all shading groups will behave as if there is no displacement shader attachment. This is a useful thing to disable at a global level when doing low quality test renders.

#### Bucket Size

The renderer renders images with a tiling algorithm, resulting in much lower memory usage. It may be advantageous to increase the size of these buckets to make very simple scenes render quicker, or to reduce the bucket size for memory intensive scenes.

#### Bucket Stride

For PRMan with multithreading.... this determines the number of buckets will be clumped together into a larger bucket, it's blocks of this size that are the distribution granularity for the multithreading scheduler.

#### Bucket Order

For Air, the 'default', 'horizontal', 'vertical' or 'spiral' options are valid, determines what order the buckets are evaluated regardless of threading.

For PRman, all but the 'spiral', 'zigzag', 'circle' and 'random' options are valid, determines which set of buckets will be assigned to what processor, using horizontal or vertical may help with memory problems. Note, PRman is strict left->right, top->bottom for actual bucket evaluation, this option only influences how clusters of buckets are distributed between the threads. The only way to modify actual bucket order evaluation for prman is to give Tipped Camera mode a try.

For 3Delight, the 'horizontal', 'vertical', 'spiral', 'zigzag', 'circle' and 'random' are valid.

#### Max VP Depth

PRMan 12.5 and later supports a maxvpdepth hider option that can improve performance for scenes that feature very large piles of semi-transparent geo. This setting is applied to shadow maps and other passes. See prman documentation for details.

#### Sigma Hiding

PRMan 13.0 and later supports a sigma hider option that can improve the look on things like hair without turning antialiasing settings up to the point that it hurts memory/speed. To use this feature you must enable it globally here and it will automatically be applied to any any MayaFur objects that have attribute/dice/hair enabled and will also be applied to all MayaHair objects. For other objects (ie: home grown hair procedurals) you may need to add the Attribute "stocastic" "int sigma" [1] manually with the user defined rib section of a mayamanattributes node.

#### Lens Aperture (Bokeh>

A PRMan 13 feature that controls the shape of the aperture which can be useful for special depth of field effects. See the PRMan documentation for parameter details.

#### Eye Splits

The renderer cannot tolerate primitives spanning the camera eye plane, and so they split such primitives down to smaller pieces in an attempt to get around this problem. They will attempt to split such primitives 10 times before discarding the remaining spanning pieces. This recursive splitting can be time and memory intensive, so you may want to reduce the number of recursions with this parameter.

#### Extreme Displacement

Shaders that displace their surface a large amount can end up using a lot of memory. Because of this, if the renderer sees an 'extreme' displacement, it will use a different algorithm which uses less memory. What it deems to be extreme is 32 scanlines by default, but this can be changed with this parameter.

#### Grid Size

Determines the maximum number of micropolygons to be shaded at one time. Shading large grids can be faster, but increases the memory usage of the renderer.

#### Backface Tolerance

The renderer will cull any single sided primitives that are facing away from the viewpoint. Usually this means their angle to the viewer is greater than 90 degrees. However, this can sometimes lead to artifacts, for example if displacement results in part of a surface curling back around to face the viewpoint. Using this backface tolerance option, yuo can increase the angle at which the renderer will cull primitives. A value of 20 here will mean any objects facing greater than 110 degrees away from the viewer will be culled.

#### Shadow Bias

The bias value when generating shadow maps can be set here. This is not normally needed when using midpoint shadow maps, but can be necessary with other shadow map sampling types. Increase this parameter to reduce objects that appear to be self-shadowing.

#### Z-Threshold

The renderer will only render objects into shadow maps that are completely opaque by default. Using this option you can set an opacity color, and any objects whose opacity is at least that color will be rendered into the shadow maps.

#### O-Threshold

If you have a large amount of semi-transparent objects overlapping each other, the renderer may end up spending a lot of time rendering objects when the pixel is already effectively opaque. By setting the 'othreshold' value, you can tell the renderer to assume that a pixel is completely opaque once it has reached a certain threshold, which you can specify with this option.

#### Flatness

This parameter controls how far from the true geometric surface is tolerable. The value is expressed in pixels.

#### Motion Factor

If you have objects that are motion blurred over a large distance in screen space, the renderer may be wasting a lot of time by finely shading the object. Turning this option on will cause the renderer to greatly increase the shading rate of objects that are highly motion blurred. A value of zero will turn this off, a value of 1.0 is good for most cases, and larger values for extreme motion blur.

### Shell Output

#### Display Progress

When this option is on, the renderer will output a percentage value for how far it is through the render computation. This is output to the shell that the renderer is running in.

Some renderers use a -silent flag to turn off progress while others use -progress to turn it on, either way this switch is controls it.

#### Shader Profiling

PRMan13 has an inbuilt shader profiling mechanism that can be useful for diagnosing slow renders. When enabled, each shadow, reflection and beauty rib will produce an XML file whose name is a simple permutation of the rib name, ie: 'foo.10.rib' will produce 'foo.10.rib.profile.xml'.

These XML files can be viewed in any modern web browser and more information on them can be found in the prman manual.

#### Output Info

Controls how much informational data is output by the renderer. You can get various levels of rendering statistics.

Note that PRMan13 writes the statistics to an XML file. MayaMan directs that XML to a file whose name is a trivial permutaton of the rib file name, ie: 'foo.10.rib' will produce 'foo.10.rib.xml'.

These XML files can be viewed in any modern web browser and more information on them can be found in the prman manual.

### PRMan11 Micro Polygon Cache

Control the micropolygon cache used by prman11 and later.... see prman documentation for details.

### Air Light Max Dist

Enable auto setting of the Air's light/maxdist attribute on a per light basis... the distance at which the light's intensity (based on the light's decay rate and intensity) falls below the threshold is set as the light/maxdist parameter... unless a light attributes node has been added to the light and the maxdist set explicitly.

MayaMan Help Contents