Clamp reflections

[gilpo]

Got a question, or perhaps a wishlist item.

I'm doing an interior scene using vray sun and sky and physical camera. I have a scene outside and am darkening the exterior in post by using a mask generated by the multimatte element. However, because the exterior is very bright at render time, any object that reflects the outside has overbright spots on it. For large objects, this is not an issue and they make nice highlights. However, for small objects or things far from the camera, I get a sparkle effect (as noted by many on the forum when lights are set to visible, however, mine aren't).

I know that using the subpixel mapping and clamp output will fix it, but I am working in full float and can't clamp. I have subpixel on, and it helped, but not enough. If I increase sampling to smooth out the highlights, render times go from minutes a frame to hours a frame (doing an animation).

So my question is this: is there a way to clamp reflections only? In my particular scene, I don't care what the reflections look like, as long as they don't 'sparkle'. From what I understand, clamping them would take care of that. But I need the frame as a whole to be unclamped.

Any ideas?

Thanks in advance.

[joconnell]

Best bet is motion blur to smooth the lot - any of those single pixel reflection hits will smear out a bit and reduce the issue. Even try a vector pass and reelsmart motion blur.

[xenry]

you can do that with vrayoverridemtl, e.g. change the materials of the outside object to have a darker version of its mtl in the reflection slot. also you can use a non sharpening antialiasing filter like blackman.

[^Lele^]

Say your reflection pixel is around 10.0 float (as picked from the vfb), and your reflection color is 255 white (1.0 float).
To have that reflection look the same in the render, but give he AAser a bit of breath, you'd have to turn it down to around a tenth of what it's now (provided you're working linearly).
Simply add a vray color map to the reflection slot of the reflective material in question, set its color to 255 white, and lower the rgb mult to 0.1.
This will have the previous reflection be in the 0-1 float range, and lower the amount of work the AAser has to do.
Of course, change the multiplier number to whatever fits your bill.

[gilpo]

Lele, your tip was so promising. I've been playing with this idea all morning, but unfortunately, it darkens the whole reflection. So a chrome material turns into a dull gray with very little reflection. Basically, I just want to apply something like an exponential color-mapping curve just my reflections on a handful of objects. Any other ideas? Anyone?

And no-go on tweaking the exterior materials. There's way to many.

Boss said no on the motion blur. He thinks our animations are too blurry as it is with the quadratic AA filter. (he's used to seeing our stills)