help needed on the basic setup cause it causes trouble later

[tunes]

hi, i have been working with Vray for a while now, but i keep running into the same trouble with the settings every now and then. I tried doing some research on it in the books, but i guess i am the only one that does not fully understand how things really work because most books/tutorials skip the setting up part.

 

The problem is this... i import a lot form autocad into 3dmax, in autocad we work in millimeters.

if i put my unit setup to generic and the system unit scale to millimeters i continuesly have trouble with shadows and have to blow up my lights big time. So the question is, how does the unit scale influence the shadows etc.

I tried rescaling the worldunits on my selection by a factor of 1000 but that made some parts shrink and others stay big. Scaling them down the normal way doesnt seem to alter their behavior on the shadowpart.

 

furthermore i also have the impression that VRAY is made for a standard scalesetup since i get a lot of trouble with spots and grain in my renders.

 

i hope anybody can shed some light on these points or point me towards a comprehensible tutorial that adresses these issues.

 

many thanks

 

tunes

[CliveG]

Seeing as there's no better reply yet I'll offer some of my very simple observations.

 

Like you I import virtually all of my modelling from AutoCAD and have very little issue (with that anyway!). I employ millimetres in AutoCAD and millimetres throughout in MAX. I use Linear Work Flow which lessens the reliance on "pushing" lighting to achieve realistic lighting results (obviously I guess; this would include shadows)

 

The only glitch I've found is a sensitivity within MAX to the models proximity to the 0,0,0 co-ordinate. If you model just anywhere in AutoCAD then import that to MAX you may create problems. (It seems to prefer 0,0,0 nearby). Likewise I understand that poorly intersecting faces etc. are a well known source of issues as well, but if you model well in AutoCAD this shouldn't be a problem.

 

I don't know why you'd use Generic units, but would be interested in the rationale, however it seems logical to me to have everything in mm.

 

Good luck.

[avvid]

Yeah, generic units are kind of wishy-washy. I think V-ray works better with proper units.