color changes with rendersize??

[skogskalle]

hey!

got a strange problem... maybe Im missing something obvious here, but I dont know so here we go....

Below are two renders... one shows an entire scene, and the other one is a closeup of one of the grass areas.
Both renders come from the same scene, and no material or light settings were changed between the renderings. The only difference is the rendersize. The smaller one was rendered 800 pixels wide, and the closeup was rendered 4366 pixels wide (for print). (I made it smaller in PS so It would be easier to post it here).
See how different the grass color is in the two renders? The grass in the big render is way too bright and is missing all the nice color-shifts that the smaller one has.
why??

Could GI settings affect this in any way? or what happened here??

The grass is made with Vray displacement modifier.

If you need settings just tell me what you need to see and Ill post a couple of screens.

thanks.

//
Kalle

[RErender]

looks like it dropped your grunge map, maybe try changing the fillter type on the map if it is summed area and/or try bitmap paging

[skogskalle]

thanks for the reply! but Im afraid I dont get what you mean... whats a grungemap? change the filtertype on what map?? the diffuse? and whats bitmap paging?

sorry... but could you please explain a bit more please?

thanks

[RErender]

do you have a noise map or something to randomize the color or is it all just by the base map?

[skogskalle]

the diffuse is a mix map with a black n white bitmap (not a noise-map but a noise-ish handpainted bitmap) in the "mix amount - slot"

[vlado]

What are your GI settings for the two images and what is the antialiasing filter/AA settings?

Best regards,
Vlado

[skogskalle]

Vlado - here are some settings for the final render. I did the GI at half of the render resolution... could that be a problem with displacement or something?

the settings for the smaller render (where the grass looks good) were probably almost the same -3 -1, but with even lower subdivs and samples, since it was just a quick test.

thanks

[samuel_bubat]

I experienced similar effects, too.

I think this is caused by the gi quality.
If you look at the first pic. You see very big color differences
(splotches) on the grass
This makes it look (accidential) very natural. You can also see that there are some spots that are much brighter btw. as bright as the grass in the
second picture.

On the second picture you are much closer to the grass.. and the gi can recognize all the details. The splotches from the first pic disappeared
and the tiling of the texture gets visible. Also the grass gets as bright as
the brightest splotch from the first pic.

Increasing the gi settings in the first pic should make the grass look like
in the second pic. And maybe decreasing the settings (especially min/max
value) in the second pic could make the grass look like in the first.

well.. this is just an idea and maybe completly nonsense

cheers

[skogskalle]

thanks samuel!

maybe youre right... but take a look at the ground. It also uses Vray displacement but still looks pretty much the same in the two pics???

[samuel_bubat]

well.. the ground displacement produces an effect similar
to a bump map, while the grass displacement produces heavy and
very detailed geometry.

But before I start telling a story of min/max values that might be nonsense
you should just check it out as described above.
Decrease your gi settings in the the second pic, and see if it looks
like the first.. that´s maybe worth a test !

cheers

[skogskalle]

thanks again samuel, but it didnt work. Im rendering a big version now, with really low GI settings, but the grass looks just like in the previous big version... too bright and well, ugly

how does the Vray displacement work? is its quality depending on the rendersize?

[percydaman]

great looking grass btw. would like to see your settings for that.

[RErender]

It really looks like the problem is in the material, maybe post it's settings, are you using explicit mapping or?

[skogskalle]

RErender - yup, im using explicit mapping cords....

percydaman - thanks, but I cant take credit for the grass. I used a grassmaterial that someone (think it was natty, not sure) posted here a while ago. Then, to get the light/dark colorshifts I made a brighter version of the same material and mixed them with a mix-map.

is there a simple way to save a material to a zipfile and have all the bitmaps being saved with it? if so I can post it if you want to... but as said, I think its pretty much the same material as the one posted here earlier.