Making Final Gather rays reach further??
 

I'm rendering a very simple scene in mental ray. No lights, just an incandescent whiteboard to use with Final Gather to illuminate a cylinder. (see picture)
I wanted to make the shadow on the floor much more visible, but the light falls off too fast before it has chance to illuminate the ground below.
Is there any way to make the light from the whiteboard reach further?
I've tried editing the Final Gather falloff start/stop parameters, and I can only reduce it further, not icrease it.

I've also tried scaling up the amount of light from the whiteboard, but to get it to reach further than the cylinder, the front ends up being completely washed out.

Make the plane bigger!

just have to change the environemrent color.you can find it in your camera attr.

Thanks, but as mentioned I tried scaling up the amount of light from the whiteboard (either via size of plane, or incandescense/ambient intensity), but to get a decent reach, the image gets washed out.The other problem with scaling it much bigger than the object is that it starts to illuminate more areas that should be in shadow. The picture shows the plane just big enough to get a visible shadow, and both prolems can be seen.

For anyone else learning FG like me, in the end, I faked what I wanted by adding a very low intensity spotlight. (Turning on 'Secondary Diffuse Bounces' also helps, but doubled render times.)

mc-fleury: thanks... yes it illumintaes the scene more fully, but also illuminates the shadow area. (I guess I could build some geometry to block the environment light from the shadow area!)

Oh i see now... how culd i be so stupid!

Create an area light with intensity 0. Thats the solution that I use, but, then again, not all things that work for me work for you.

the size of your plane does matter.

to get better results, select your lightsource, in this case the plane,
in the incadescence color attribut simply put the "v" value to a number greater than 1, something like 10 should do fine. and set your fg rays to something like 300

here i simply added a blueish tone.
preview final gather render setting>fg rays to 250

one point light set intensity to .0001 so that default lights are not used.

This was done quick but it should get you going.

Download the Maya 6.0 file from here.

Cheers
Paul

vladimirjp: Thanks, I didn't understand at first because as I said initially, ramping up the light value from the whiteboard washes things out. After a bit of experimenting, I'm guessing that didn't happen in your render because you moved the whiteboard further away to compensate.(?)

BMS: Thanks for the file. I learned a lot from looking at it.It looks nice with the camera environment color right up to light the scene. It does tend to lose the shadows though.

But thanks guys, by fiddling with both solutions I've found a middle ground that works well