hi all, a couple of questions:

1. i have a sphere around the scene to give a sky background. my GI light is inside the sphere, but always renders black unless i remove the sphere, as though the sphere is blocking them but it isnt… any ideas on that one?!?

2. Ive made a box, then added vex mountain SOP with the following function in the frequency fields: fit(rand(1.454), 0, 1, 0.5, 1.5) to get some random values.

but when i make copies of the object the values of all objects are the same, they arent different across each copy. is there a way to do this, effectively randomise the seed? id rather not copy the object then attach a unique vex mountain to each instance.

cheers

no idea about question 1, but for the second one, I think you need to feed the rand() function with a different argument for each “copy” in order to get different values from it. If possible, put them all in one object and use copy stamping, then you have access to $PT as an argument for rand().

If this is not an option, you could try using the opdigits expression inside your argument. I never used it, so you need to look it up in the expression pdf.

GI in mantra works by taking light from the environment when rays bounce off into space. Since you've enclosed your whole scene into a sphere, then none of the bounced rays can get out.

If you just want a background image, it's much better to do it at the compositing stage. Or perhaps render out a separate pass if you need to.

You need to remove your sphere from your gi light's shadow mask.

great help, thanks a lot all