Extremely Grainy Result in VRay Exterior

[JamesTaylor]

I'm trying to render an exterior scene using IrridanceMap Primary and Photon Map Seconary bounce. i've attached all my settings, a sample render, a render of the photon map and a viewport screen grab from viz.

 

as you can see from the sample render the result is extremely grainy, i've plyed with many different settings but the final render never seems to change. any suggestions as to where i'm going wrong would be much appreciated.

 

I can post the scene if its any help.

 

thanks in anticipation

 

James

[siliconbauhaus]

I'm curious as to why you would use photons for a external scene. I would just use a sun with vray shadows and environment and then use irradiance map / qmc

 

It looks like you have some modelling issues around the crown moulding so maybe set the secondary ray tracing bias to 0.001

 

I'm not a big fan of photon mapping but have a look at

http://www.chaoticdimension.com/forums/phpBB2/index.php

and search for posts by goncalop he did some studies on using photon maps

[JamesTaylor]

Patrick,

 

First of i've only just started using Vray, and got a lot to learn by the looks of things!! The reason i am using photom mapping is i'd been playing using the same techniques last night on an internal scene and managed to get some decent results, so am trying to transfer that knowledge across to an external render.

 

However, i've given your suggested method a try and have found it to be unbelievably slow (not having a go, i'm probably doing something wrong most likely). So slow in fact that i quit the render as it just was not practical, especially when i'm only render at 640 x 380. I've got the 1.46.10 version of Vray and have read many posts on the link you supplied quoting the same issue of slowness but no real answers to problem.

 

When rendering the attached scene i've tried many options including the defaults with no adjustments but can't get anything to change in the final render. Do you have any suggestions as to which settings may have the biggest impact on time and quality?

 

thanks

 

James

[Craig Ramsay]

To start off with dont use a huge area light. Your best bet is to use a slightly yellow/orange target direct with Vray shadows for the sun and maybe a blue vray light set to dome for your soft skylight.

 

Photon mapping is not good for outdoor scenes and I wouldnt bother using light cache either. If you need global illumination then use the irradiance map and start with the default settings, they should be good enough.

 

Craig

[siliconbauhaus]

I agree with Craig's view. I use the irradiance map with qmc at it's default settings for most things and I've never had renders take very long. You should pop over to evermotion as well for ideas. Between the vray forum and evermotion I've managed to teach myself how to drive it fairly well.

 

Did you mean to post your scene?

 

Oh and go download the latest version...it's .14 now

[Da_RoCk]

in addition to criags method. id also suggest that you use lightmap for exterior. It works just fine. With the bloches you have, id say that it is because of the Global photon mapping settings.

 

In response to the speed of the rendering... bringing down the noise threshold to 0 indeed will slow down your rendering. try using first the default to .005 then make it 0 when you are decided to make the final render.

 

Are you using a big vray light for a sunlight? its ok but i dont think that its a good solution as craig has pointed out. For your environment, may i suggest that you also consider using a HDRI for the environment (overrideing max).

 

These are all suggestions and based on my observation. id be very glad to be corrected.

 

GOD BLESS

[paul Ison]

personally I find photon maps a bit risky for exteriors. QMC for second bounces should be resonably fast if your settings are kept low. 3 bounces with 6 subdivisions works well with noise threshold of 0.002. If you render large, you can drop the IRmap settings maybee to -4/-2. These are the typical settings I use for exteriors. Interiors are COMPLETELY different but I would reccomend Light cache for interiors.

 

If you rendered your scene without secondary bounces it would look much better than it does currently which is due mostly to the photon mapping