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# MayaMan Raytracing Options

This dialog contains options that are specific to renderers that support raytracing. Some of these options may not be supported by the particular raytracer that your are using. For more info, consult the documentation for the renderer you are using.

### General

#### True Displacement

With this option on, the renderer will dice and displace geometry. With it off, displacement shaders moving 'P' will only affect the surface normal, resulting in bump mapping only

Note, this is not a switch to control displacement in traced reflections, it controls the default default state of attribute/render/truedisplacement... this switch exists here because it's only available in some raytracers, consult your renderer documentation to see if this switch may be useful.

#### Enable Reflection Ray Visibility

When turned off all objects will be invisible to reflection/refraction rays, this can save time and memory when it is known that no shaders will cast environment rays.

#### Shadow Casting

The renderer can use a variety of methods for determining the opacity of an object when tracing shadow rays. 'None' means that shadows will be disabled. 'Opaque' assumes all objects are non-transparent. 'Os' will use the object's base opacity setting (as does PRMan). 'Shade' will run the surface shader of an object when intersected with a shadow ray, and the final value of 'Oi' will determine the surface opacity at that point for shadowing.

#### Ray Traced Shadow Visibility

A lot of memory can be wasted if objects are visible to shadow rays when there are no lights with ray traced shadows in the scene. This switch lets you control the ray traced shadow visibility.

Auto | If MayaMan thinks there are no lights with raytraced shadows then turn off visibility to shadow rays for all objects. MayaMan might get it wrong if you use custom light shaders that do raytraced shadows in ways that mayaman can't detect.
If shadow casting | If an object is shadow casting then they will be visible to shadow rays too, choose this option if you are using custom lights that do raytraced shadowing and those lights don't have a __shadow_type parameter that is set to 2 to indicate they want to do ray traced shadowing.
No... unless radiance on | Force visibility to shadow rays off unless global illumination options are enabled that would require such visibility.

#### Max Ray Depth

Determines the maximum number of recursive rays that will be cast for reflective/refractive objects.

#### Max Diffuse Depth

Determines the maximum number of recursive rays that will be cast for diffuse ray paths.

#### Max Specular Depth

Determines the maximum number of recursive rays that will be cast for specular ray paths.

#### Specular Threshold

Determines the classification of a ray between specular and diffuse.

#### Min Shadow Bias

Sets the minimum distance that must be between objects for one to shadow the other. Increase to remove self-shadowing artifacts in raytraced shadows.

#### Max Curvature

Controls the quality of tesselation of paramatric surfaces for the purposes of raytracing.

#### Importance Threshold Fade/Cull

As of MayaMan 2.0.4 the casting of reflection and refraction rays for recent versions of PRMan is limited based on the accumulated importance of the ray. When the importance of a sample is below the Cull threshold the ray is not cast at all. The the importance is between Fade and Cull then the ray is cast but it's contribution is faded off. Above the Fade threshold everything happens as before. Setting the Fade to 0 causes the original MayaMan behaviour of always casting rays until the depth limit is met. If you have a scene that features lots of reflection and refraction these controls can have a significant effect on speed.

Authors of SLCodeNodes that cast rays should review the information related to importance values so that they can avoid casting excess rays and ensure that they properly propogate the importance settings on rays they do cast.

### Misc/Obsolete?

A collection of parameters that are probably not of much use to anyone except users of antique renderers.

#### Ray Goggle

Insert a transparent surface over the lens of the camera so that the entire scene is rendered with raytracing... all scanline rendering is disabled... only for prman and even then probably only useful for experimentation.

#### Use PRMan Specular

Turning this option on will cause the renderers like BMRT to mimick PRMan's specular calculation. Without this option on, specular highlights will differ greatly between the renderer and PRMan.

#### Framebuffer Step (-d)

The renderer's built-in framebuffer display driver has the ability to draw the image in iterative steps, showing a coarse blurred image to start with, and tracing intermittent rows until the final sharp image is produced. The parameter controls how many iterations the renderer will perform to construct the final image. Ignored if not using the 'framebuffer' display driver.

#### Min/Max Samples

These controls only apply when PixelVariance mode is being used, in which case they choose how many rays will be cast. Technically speaking, they set the render/minsamples and render/maxsamples options.

#### Geometry Memory

Sets the amount of memory used by Entropy/BMRT to store diced geometry. Smaller values reduce memory use, but can cause objects to be continually re-diced.

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