Irr&LC vs Brute Force&LC comparison render

[rmejia]

I have a question about the difference in lighting & reflection in two renders. The first image uses:
Primary: Brute Force
Secondary: Light Cache

The second image:
Primary: Irradiance Map
Secondary: Light Cache

Using V-Ray Adv 1.50.00

I did the one with IRR&LC first, since it is the settings I usually use. Looking for options for final renders and perhaps some improved quality, I tried using Brute Force as the primary bounce. All other settings are exactly the same, all I did was change Irr for Brute and hit render. A clear difference is the reflectivity of the materials, and the illumination of the overall scene. Since no other settings were changed, and Brute force only gives 1 option (subdivs), what other setting could I use to lighten up the scene (color mapping?)... although my question is WHY is there that marked difference in lighting and reflectiveness. Thanks.

[Codi]

One thing that can cause differences between the two methods is subpixel mapping. In our tests bruteforce renders usually get darker than IR Map/LC if subpixel mapping is activated.

[themaxxer]

One thing that can cause differences between the two methods is subpixel mapping. In our tests bruteforce renders usually get darker than IR Map/LC if subpixel mapping is activated.

I second that. it's the subpixel mapping.

[rmejia]

I unchecked the subpixel mapping and it comes out identical (darker).

[ene.xis]

well my guess (and personal experience) is that qmc now Dmc solution always comes out a notch darker.

imHo its just because dmc is more acurately calculating the light decay, wich results in a little darker image, but crispy and with great deapth...

[Codi]

Hmm, pretty hard to tell without having the scene at hand ...

One thing that I find strange is the shadow in the upper left part of the second render, it completely disapears in the first one. This and, obviously, the lack of light seems to point that some light source stops working in your bruteforce render, how do you illuminate the room? what kind of lights do you use?

The exterior is comped or is direct from render? Seems identical in both renders.

edit: yeah, maybe is just the deacy

[Codi]

Just an idea, do you have vray lights on the ceiling with 'store with irradiance map' checked?

[rmejia]

Just an idea, do you have vray lights on the ceiling with 'store with irradiance map' checked?

Doah!

Thanks for the help ... that was it!

[RErender]

that one still gets me occasionally

[werticus]

not related to your problem, but some feedback:

the scene needs some more contrast, outside should be a lot brighter, you've got light bulbs brighter than your sun at the moment that could be what you / the client wants, but its not realistic.

[Codi]

Thanks for the help ... that was it!

Your welcome. It was a tricky one

I don't know if there is a reason to have VRay Lights behave this way when you don't use IR map instead of ignoring the checkbox.

[rmejia]

not related to your problem, but some feedback:

the scene needs some more contrast, outside should be a lot brighter, you've got light bulbs brighter than your sun at the moment that could be what you / the client wants, but its not realistic.

I agree. The thing is that part of the selling point is the view to the beach and ocean. Whats outside the windows is really important to show. There are 3 other views that show more of the exterior. I did some renderings with the outside brighter but it turned a couple of things to white, like the beach and parts of the sky, making them unrecognizable. I have two vray plane lights on the ceiling to brighten up the whole space inside (unrealistically). But yes, every time I look at it, the background seems dark (in part because the interior is bright). I will try in photoshop to brighten the background image, while still trying to preserve the colors.

[gagui]

i'm having a similar issue in a scene where only changing the AA settings from Adaptive to DMC i get a much darker reflenctions (crome object).
I have subpixel mapping on, could this be the reason?

[vlado]

I have subpixel mapping on, could this be the reason?

Yep, this could be a reason.

Best regards,
Vlado

[Sushidelic]

Just thought about a little prerender callback to check if everything about the "store with irradiance map" tickbox regarding GI is setup correctly. So here it is.

macroscript CheckVraylightsCallbackON category:"sushidelictools"
	(
	callbacks.removescripts id:#vraylightchecker
	mycode = "vraylightcheck = getclassinstances vraylight \n"
	mycode += "vraylightchecktrue = \"\" \n"
	mycode += "if findstring (renderers.current as string) \"v_ray\" !=undefined do \n"
	mycode += "(if renderers.current.gi_on != on or renderers.current.gi_primary_type != 0 do \n"
	mycode += "(for i in vraylightcheck where i.storeWithIrradMap == on do append vraylightchecktrue (exprForMAXObject i+\"\\n\")\n"
	mycode += "if vraylightchecktrue.count >0 do \n"
	mycode += "(vraylightchecktrue += \"\\nuse store with irradiance map and will not render\ncorrectly with your gi settings\" \n"
	mycode += "messagebox vraylightchecktrue )))"
	callbacks.addscript #prerender mycode id:#vraylightchecker
	)

macroscript CheckVraylightsCallbackOFF category:"sushidelictools"
	(
	callbacks.removescripts id:#vraylightchecker
	)

Not really errortested, but here it worked. If you register it, it checks your scene for vraylights that have the "store with irradiance map" option ticked. If there is at least one that does, it looks at your gi settingsand checks if gi is enabled and if irradiance map is used. If this is not the case, it prints out a warning.

Best regards,
Michael