VRay blotches

[andrew.forbes]

Hello everyone,

 

Have a look at the attached image and see if you can give me advice on the blotching that appear pretty much everywhere on the building. I think it might have something to do with the sampling but an experienced suggestion would be very handy as a quick fix is needed.

 

Oh, and any other comments would be useful too!

 

Thanks guys.

[TraP]

hi

U need mor subdivs on the sun light, and U'll get better resoult

 

waiting 4 update

[andrew.forbes]

Hello again,

 

This is my most recent render after having increased the subdivisions on the light source and tweaked a few things... the blotching has reduced but is still apparent. The problem I am having is that it takes an amazing 14hrs:mad: to render!!! So i have to leave it rendering overnight. Maybe something to do with the fact I am rendering 4690x3507px @150dpi that equates to 84x60cm. Pretty large, but this is what the client has asked for!

 

Is this massive rendering time due to the fact that VRay is sampling on a per pixel basis and therefore having to calculate samples relative to the size of the output??

 

I have tried a few things to speed up rendering, i.e. storing the light with the irradiance map and adding a HDRI to reduce the amount of light needed in the scene, which has helped as the first attempt took 18hrs to render. The blue tint is from the HDRI i added into the skylight but i think i will remove it for next time.

 

I suppose i could just increase the subdivs even more and leave to render over the weekend but I'm sure there must be a better resolution to my problem.

 

Your comments, as always, will be helpful.

 

Thanks.

[Iain Denby]

all my visuals are rendered out at 4500 - 5000 px in the longest dimension. It needs to be to get a decent A3 @300dpi.

[andrew.forbes]

Do you get these ridiculous rendering times?

I'm relatively new to the game but I would have thought there would be a way to reduce them.

 

Another problem could be that the model was produced for interactive VR purposes (i.e. the whole building was modelled, inside and out!) and therefore there is a lot more detail than is needed for rendering this scene on its own. I tried to reduce the geometry as much as possible for the scene, with the obvious time constraints.

 

Cheers.

[erickdt]

I wonder what GI methods your using in you indirect illumination. By the looks of it you're using photon mapping for both the first and second bounce (?). If this is the case you should change your first bounce to irradiance map and then have your second as photon map. I personally use irradiance map first and the qmc for the second. It seems like alot of people on the forum use ir map first and then light cache for the second.

 

Hope this helps!

[andrew.forbes]

I use Irradiance map for first bounce the QMC for second.

 

I tried a light cache for the second bounce but my PC just froze...

 

It probably doesn't help that I'm only using a single 2.6 processor with 1G RAM.

[andrew.forbes]

Here is the final render. I ended up using a photon map in the secondary slot, and irradiance map for primary.

 

Thanks for the advice guys.

[kippu]

why photon map .. in exteriors... why not light cache....

[andrew.forbes]

Hmmm.

Light cache you say?

 

I'm still pretty new to VRay (only had it 2 weeks), the photon map cured my problem of the blotches but did take an awful long time to render. I will try light cache next time perhaps.

 

Thanks,

still learning