heat haze with volumegrid

[robin_lawrie]

hi. looking to do a heathaze on a road. ive seen this post:
https://forums.chaos.com/forum/v-ray...at-haze-effect

and a couple of others, but im wondering if it is possible using only the volumegrid and 3dsmax, rather than simulating in phoenix.

it seems that using some combination of gradient ramp and noise to drive the volumegrid in texture mode might be doable and would (i hope) be easier to fine tune.

however ive not managed to get my head round how to do it. any pointers most appreciated.

[hermit.crab]

We tried recreating the Haze without a cache, but to no avail - a cache (with a temperature channel) is needed. I think if you are not willing to simulate, it would be easier to create the effect via a refractive object in front of the camera or in post.

[robin_lawrie]

i actually managed to get it working in a basic proof-of-concept kinda way, using textures to drive an empty volumegrid, however its incredibly unstable, i get repeated crash to desktop when tweaking the textures with ipr active, and some very odd rendering artifacts in ipr ( after a certain number of passes the entire volumegrid goes pink or yellow)

im preparing a simple scene to upload

[robin_lawrie]

ok i manged to get something that works ok, however i still have issues with stability, ive tracked it down to the step% parameter. too low and it crashes to desktop when i render. obviously i get the same result if i make the grid too big or the cells too dense. its strange though. i could understand it taking longer to render, or using more ram (its not using even half my ram) but crash to desktop? ive now got it rendering stably, but i would prefer to have a lower step % some artifacts are visible in the effect.