scanline vs raytrace


what is the main difference between those 2 MR renderers?

is there any visual difference in the rendered images?

why is scanline turned on by default?


Scanline only: no raytracing. No refractive transparency or accurate reflections.

Scanline primary with raytracing secondary: best of both worlds. Scanline rendering is faster than pure raytracing, but in this mode you’ll get your reflections/refractions. The scanliner will render elements of the scene which don’t require raytracing, while the raytracer will handle reflections/refractions, soft shadows, etc.

Raytracing only: slower, but more accurate. Everything is raytraced.


then why is scanline superslow with 3d motion blur?
i had a big scene where i was never able to render it with scanline and 3d motion blur together (it was super slow and MR went out of memory), what saved me at the time was raytrace instead, wich rendered alot faster and didn’t run out of memory.


…and a host of other features.

Scanline doesn’t support 3D motion blur, nor 2D, as far as I know.


For faster rendering with motion blur, you should set the Primary Renderer to “Rasterizer” instead of Scanline or Raytracing. You still get to use Raytracing as long as it’s on under secondary effects. You do have different anti-aliasing controls in Rasterizer, though.



raytrace will also make grainier texture filtering than scanline

with scanline, you can put your tecture filter to 0 and if your doing still shots with 2 max samples, it will produce nice texture filtering. However these same setting with raytrace will be too grainy, with raytracing, the texture filtering needs to be at .3 to get the same quality.


I would add that you should set your primary to Raytrace if you are rendering volumetric effects, fluids, or particles with the cloud shader (or fluid shader).

Also, I’ve noticed some instances where primary as raytrace is faster. I think those times involved instances and possibly motion blur, though I tend to utilized the Rasterizer for motion blur where it doesn’t create artifacts or instability.


but you wouldn’t obtain motion blur in reflections…

do you have any visual exemples?


Sometimes mental ray can’t handle motion blur and reflections regardless of mode :slight_smile:

It’s really rare that motion blur on reflections is big issue though- unless you’re rendering a bunch of T-1000’s in a hall of mirrors…


no, but it’s pretty easy to replicate

bring in a grainy texture like dirt or sand on a typical maya file node
Set the filter slider on the file node to 0
put this on something
then zoom the camera far enough back so that the texture will have to be filterered
and position it so the surface is at like a 45 to 70 degree angle tangetial to the camera
render it in raytrace and scanline. Raytrace will be much grainier


I just checked and indeed mental ray fails to blur it correctly with fast rotating objects. It has something to do with motion but not surface.


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