Final gather and glass materials, just some advice.

[djwang]

i ve noticed that if i add a glass material to scene then precompute the FG map the calculation times can go up dramatically. the whole point of precalculating the FG map is to save time and free up resources during render time.

just wondered if their where any tips about optimising FG for such materials.

 

 

many thanks

 

DJ

[jinsley]

I have switched off the glass layer before and then done the FG calculation... locked the FG, switched the glass back on and then rendered.

[Justin Hunt]

I tend to set all glass objects to "Pass through" and not generate Photons.

 

jhv

[djwang]

I have switched off the glass layer before and then done the FG calculation... locked the FG, switched the glass back on and then rendered.

Does this eefect any detail behind the glass ? ive tried this but found what is behind the glass becomes a little murky. for instance travertine tiles.

 

Also jinsley

 

whats better to increase FG points or interploation points ? am not even sure what they do i just know if i increase them i get better colour blending and less artifacts but at the cost of time. id like to have an in depth understanding of this parameter of mental ray could you recommend anf books to read ?

 

thanks again bro

 

thanks Bro

[djwang]

I tend to set all glass objects to "Pass through" and not generate Photons.

 

jhv

 

Am gonna sound like a complete ameatuer here (but i am.lol) but when you say pass through meaning its not even calculated in terms of GI and FG. does this amke the glass darker as its not recieving photons to illuminate it ? so what ever is behind it will also be aliittle darker ?

 

 

thankyou

bro

[Justin Hunt]

it will still receive illumination but will not effect the fg samples passing through it, ie diminish its energy of change its colour.

It is also receiving direct lighting. What ever is behind the glass will be brighter as its receiving more fg samples.

 

jhv

[djwang]

thanks justin , works a treat