When I render, if I zoom in, I can sometimes see a tiny gap in the alpha channel where the Fur grows out of the surface.

This problem is caused by the Fur growing out of the edge of the geometry, which is anti-aliased - there is a one pixel area of anti-aliasing before the Fur alpha begins. This gap is not usually noticeable unless the Fur is very sparse and/or the background color is very contrasted to the fur color.

Solution: Set the Offset value for the Fur Description to be a small negative number. This will cause the Fur to grow from slightly inside the geometry, eliminating the gap.

When I render, there is a faceted gap between the edge of my NURBS surface and the hair growing out of it.

The Fur renderer uses a default tessellation factor for NURBS which is quite high. If the geometry is tessellated at a lower tessellation, you may see a mismatch in the final composite.

Solution: Increase the tessellation on the geometry, or decrease the tessellation used by Fur ( Fur > Fur Render Settings > Advanced Options).

When a non-furry object passes in front of a furry object, there is a fringing effect around the foremost object.

In the Maya software renderer, Fur is composited with the geometry internally using Z-depth information. Because Z buffers are not anti-aliased, in certain cases, fringing can result when there is geometry in front of the fur.

Solution 1: Render at double size and then scale down the image, or render in separate passes and then composite using alpha channels.

Solution 2: Select fur-emitting object and assign it to a new render layer. Then, select both fur-emitting and furry objects and assign them to a second render layer. In this second layer, override Primary Visibility for the fur-emitting object. Render all layers.

Solution 3: Render using mental ray for Maya since mental rays renders do not exhibit this problem.

My Fur render is extremely slow - is there anything I can do to speed it up?

Fur render times increase linearly with the number of strands of fur used - rendering 10,000 strands of fur will take twice as long as rendering 5,000 strands of fur. Shadow map calculations take as much time as the render itself for each light with Shadow Maps turned on for Fur; for example, using two shadow maps will cause your render to take three times as long as using no shadow maps. Conversely, Auto Shading is virtually free, and gives realistic back and root shading.

Solution: Try using fewer strands of fur with a broader Base Width to get good surface coverage. You could also reduce the number of Segments, particularly if the fur is straight. Limit the number of Fur Shadow Maps you use to one or two at most, and instead use Auto Shading or No Shading for most of the lights.

How can I render Fur through refractive material - for example, an eyebrow and eyelashes through spectacles?

In the Maya software renderer, Fur does not show up in raytraced refractions and reflections, but it is possible to fake some effects, including this one. Note that the following technique will work equally well for Paint Effects.

Solution: Render the full scene with the Fur, but with the spectacles lenses hidden. Next, create an image plane (Display Mode RGB, Fit to Resolution Gate) using the above image, toggle on Visible in Refractions, and interactively change the Depth value until the image plane sits just behind the backmost part of the lenses (you could set up an expression to accurately track this if needed). Render the scene again with only the raytraced spectacle lenses and frame, and the image plane (hide everything else and turn off Fur rendering). The image plane containing the Fur will be refracted through the lenses. Also remember than Fur will refract and reflect correctly in single render pass within mental ray.

Can I render just the fur images using the batch renderer?

You can disable the Maya renderer and render just the fur images with the batch renderer.

Solution: Set up your scene as usual, and then turn on Disable Maya Rendering under the Advanced Options of Fur Render Settings.

I'm running out of memory when using Fur. Is there anything I can do to optimize memory usage?

You can control the number of hairs tracked per pixel for both the fur images and the shadow maps. This is trade-off between quality and memory usage. You can also reduce the size of shadow maps used for Fur, since using large shadow maps is extremely memory intensive.

Solution: Reduce the Hairs/Pixel value for both Fur Image Rendering and Shadow Map Rendering (where applicable) under the Advanced Options of Fur Render Settings, especially in scenes where your character is the distance. Don't use a larger shadow map for Fur than you require, and use Auto Shading instead wherever possible.

My Fur seems way too bright, especially the specular highlights. Can I fix this?

Firstly, you need to understand how the Fur color is calculated. Fur adds together the color, the ambient color and the specular color (depending on your light model), and multiplies the result by all of the light intensities. So if you have several lights with intensities higher than one, you will quickly see very bright highlights.

Solution: To compensate for this, set the specular color to very dark. To break up the highlight, map the specular color to a fractal or brownian, again using dark colors. Don't forget to Bake when you are satisfied. If the specular highlight is too large, set the Specular Sharpness to a high value - 200 or more is fine. If you can't resolve the lighting which looks right for your Fur and the lighting with looks best for your geometry, you can use the Intensity Multiplier value to change the effect of the lights on the Fur only. The Intensity Multiplier value is part of the Fur Shadowing Attributes which can be added to any light ( Fur > Fur Shadowing Attributes > Add to Selected Light). Note that you can set the Fur Shading Type to No Shading, and still adjust the Intensity Multiplier.