Light and Material problems

[HasseB24]

hey..

Im a newbie in Vray. I am having problems with my renders. I've uses linked SU materials in vray. when i render it shows all sorts of colors.
I am using sunlight as my only light source.

If anyone have seen this before, i would very much like some help

[dcauldwell_cg]

Re: Light and Material problems

If you are using sunlight, make sure you are using the physical camera, and set the correct exposure, say shutter speed - 125, f-number - 8.
Sometimes extreme brightness causes strange colour reversal, if not using the correct exposure.

David

[HasseB24]

Re: Light and Material problems

Hey dcauldwell.

thank you for your fast reply. I am using the default settings.

To configure the skylight im using a tutorial from this page.
http://asgvis.com/index.php?option=c...d=35&Itemid=56

Here the shutter speed is set to 125 and the f-number to 12.
but it still turns out wierd looking.

Other settings.

Global settings
Filter maps - Disabeled
Default light - Disabeled
Gamma Output - 2.2

Environment
GI - 1.4 Light blue
Background - 1 Light blue

Image Sampler
Min subdiv - 1
Max subdivs - 16

Indirect illumination
GI - enabeled
Primary engine - Irradiance map - 1
Secondary engine - Quasi Monte-Carlo

Irradiance Map
Min rate - -3 Max rate - -2
HSph. subdivs 30
Samples 20

Materials used.

Concrete 4 from this site.
Applyed the bitmap as a SU material and then linked it to the vismat material.

I hope these numbers could give some answers.

HasseB24

[dcauldwell_cg]

Re: Light and Material problems

it would help if you can post an image (need to use imageshack etc to post).

Also try:
Irradiance Map
Min rate- -6, Max rate- -1
HSph. subdivs 70
Samples 20

and maybe check 'clamp output'

David

[HasseB24]

Re: Light and Material problems

here is the test renderings i've made.

[bones_cg]

Re: Light and Material problems

How long you rendered this scene ?

[HasseB24]

Re: Light and Material problems

i dont know the exact time, but around 5 to 10 min. i think.

[dcauldwell_cg]

Re: Light and Material problems

Did you try 'clamp output' (in color mapping)?
If its not that then I am stumped.

The next thing I would do is to try a different vsopt - gi_irmap_medium.visopt (always a good standby!) While I await the cavalry!!

David

[HasseB24]

Re: Light and Material problems

This is the render with Clamp output turned on.

The white box in front should be the concrete material and the rainbow coloured boxes behind should be white.

[dcauldwell_cg]

Re: Light and Material problems

You really need Damien on this one!

But while you wait (!), I feel it is something to do with the light intensity, creating a sort of (photographic) solarization effect. Check that you havn't inadvertantly increased the sun intensity in the 'environment slot'. It should be set at 1.
Also, in the render frame, while it is rendering, try checking and unchecking the 'force color clamping' button (at the bottom, second button in). I notice that this can give the strange colours you have experienced.

Good Luck

david

[dalomar_cg]

Re: Light and Material problems

Sorry for sleeping guys...I'm on the case ;D

Well, there's something going on in the scene for sure, but as far as the actual rendered output, thats simply an issue with the frame buffer...So hopefully you know that Vray calculates colors that are beyond white. This is a good thing, but the "tricky" thing becomes how do you display colors that are brighter than white bc our monitors aren't built for that kind of thing. The simple answer is don't (just leave the R,G,or B value @ 255...this is known as clamping), but there's a little tiny option within the vfb that will allow the display of those values.

The vfb's solution to how the colors will display is to just start back from the bottom of the spectrum again. Therefore if I have a color thats almost white (250,250,250 lets say) and the green value gets tipped past 255, the vfb will now display the color as 250,5,250 (5 -> 250+10=260-255=5) which is radically different from the just barely brighter than white that the color actually is. When you apply this as a whole over the image your results typically are a very trippy mess of radical colors.

So now for the solution. The second button on the bottom left of the vfb will force your colors to only display to white, and will remove all of the weird cyans and magentas from your rendering.

So now for the real solution. After you click that button, you'll have essentially a white image. Now you're going to have to go back and decrease the exposure of the physical camera to accommodate for all of that brightness. What you're looking to do is to keep those rendered values within the visual range, and that will help things out a lot

For my sake, I hope this is the issue, or else I've blabbled on about practically nothing : )

[HasseB24]

Re: Light and Material problems

i've tried what you wrote. i am now working with a gi-irmap medium setting where i've changed to physical camera

Shutter speed - 125
F-number - 8

Environment
GI - 1
Background 1

It now looks like this when i clamped the colours




What do you think i should do now. it seems decreasing the GI to 0.0001 does not have an effect. should i increase instead?

[dalomar_cg]

Re: Light and Material problems

Hmmm...guess I blabbled on about nothing

Load this visopt and see what happens. If it turns out black, add a rectangular light into the scene or something.

http://www.box.net/shared/vykn77bbxh

Basically I have no idea if this is just vray gone crazy or an odd combination of settings and scene, so hopefully this will get a starting point to see whats really going on.

[HasseB24]

Re: Light and Material problems

Thanks for the old default settings.

I've tried rendering with the new settings, but it was still the same.

Then i created a rectangular light making the multiplier to 0.001 and disabeled the linked materials in the scene. Now the lighting seems to be okay



However when i add a material again, it turns out wierd looking again. Here the multilplier is set at 1



So im guessing it has something to do with the Vray material im using.

[dalomar_cg]

Re: Light and Material problems

Okay, it looks like we're getting somewhere. The material thing quite possibly could be at the root of the problem...do you mind uploading the material and any maps that may accompany it? via email works fine too.