mental ray sampling problems

[djwang]

hi all thanks for reading my thread.

ive been struggling for some time now to master the sampling capabilities of mental ray.

i'm a bathroom designer by profession and its not really the products and chromes i ve had trouble expressing. its been more the grout lines between tiles. in my industry we usually go by the rule of thumb that the space between each tile is 3mm. but for the life of me, regarding some tiles i cant get the grout lines to be depicted. i ve used vray doing this with out any problems. but when i bought my new workstation 3dsmax 9 and vray sp1 wont run on it, something to do with the amount of cores my machine has. so i started to use mental ray instead ( i now have vray but it renders stupidly slow, and ive been with mental ray now for 3months so i decided to stick with it).

if the tile is dark the the white grout lines displays crisply, no probs but say the tile is like travertine more creamy and golden then the grout line vades into the wall. its a pain because clients like to see informative images. and putting every grout line in using photoshop witch ive done before but it makes me want to scoop my eyes out with rusty spoons and make them as an offering to mental ray. lol

 

ive heard of spatial contrast but struggled to find much info regarding the topic and how to utilise it.

 

ill post some images to show what i mean

[jinsley]

I think that is nature of things that the more contrast between objects, the sharper they read (like black tiles with white grout)... and the less contrast the more they merge visually (like white tiles with white grout)...

 

what are your render settings? maybe you can tweak them a little to offer more definition between colour tones?

[djwang]

to the rescue again my friend. i dont really change the render settings. ive tried to make the gout texture imune to colour bleed using the ray switcher, i also tried changeing the a&o ambient light colour to a white which over exposes the texture, i m baffled as vray had no problems i just used the colour correction map in vray. white grout lines all the time. i would use vray but it seems to have lost its edge as being fast. many people and from my own experience it is like forever to render now. i have enjoyed using a different render sometimes your creativity can become automated so i had no problem switching to mental ray but this issue with contrast is gutting me out, as my boss has a certain espectation of the images that where produced before. even in real life you dont get this merging together grout is very prominent it catches your eyes giving an illusion of space, your eyes follow them, they are imperitive to view in my visuals

 

i really hope theirs a way to do this

 

thanks for your response & and the twisted tower by santiaga calachava is awsome, hes one of my all time favourate architexts. your works amazing.

 

 

DJ

Edited January 5, 2011 by djwang

[Justin Hunt]

what resolution are you rendering to? Often rendering to a higher res helps with sampling issues as it has more pixels to work with.

 

Side note, when using photons leave the FG diffuse bounces @ 0 , they are discarded anyway.

 

jhv

[djwang]

i usually render A3 150 dpi ive tried 220 but still same. i got some kind of result today by actually making the grout lines self illuminating but they dont illuminate the scene by turning of the final gather option but they are quite bright case of you see them or you dont i guess ?

 

thanks for the response justin

[Jennifer]

You may need to up the Image Precision (Samples per Pixel), and definitely stay away from the Box filter. Try Mitchell or Lanczos.

 

You can also turn the Spatial Contrast setting down to 0.025 perhaps. This will force mr to use the higher sample rate more often to resolve the details. Try that before using higher sampling.

[djwang]

thanks jennifer, for that ill give it ago. the only way at the moment ive been able to get a consistant griut line is to make the grout material illuminated but turn off the FG box. but it looks to strong in appearance.

how will these settings affect render times ? As ive got to get 5 images a day out at 150-200DPI plus build the scenes. i look to get about 10 mins for the pre computed final gather calculations, the 2 mins for the photon map then 20-30 mins for the final render.

 

 

 

much appriciated advice thanks

 

DJ

Edited January 16, 2011 by djwang