Mission Impossibile with Vray (at this time)

[Thecroque]

Would be very nice if Vray could make an Image like this in Future... (image rendered with brazil)






but at the moment, it is impossibile to generate something like this with vray...

for professional interior visualisations it could be very helpfully

(Lightscape, Brazil and VIZ are able to do something like this...)

[Thecroque]

Further Explanations:

The yellow wall has a different Material for receiving and sending Light... it receives white light (from the spot) on a yellow material (we see the yellow spot on the wall) and sends (bounce) blue light into the room for indirect illumination...

And sometimes I need exactly a Material like this one above... (the example is a little bit extreme... it's to show you how it should work...)

What do you think... could something like this be helpful for you too?

Thecroque

[Dusan_Pavlicek]

This behavior is obviously physically incorrect.
But if you really need this kind of effect, it can be achieved by combining two separate images/scenes, I believe.

[Thecroque]

To Dusan_Pavlicek:

I know that this behavior is physically incorrect... a yellow wall cant emit blue light... i made this example only to show you, what I really like to have in Vray...

Some Materials doesn't emit the same colour-saturation as we think they have to... and with Vray I cant set the Saturation of the material GI generation... (or place another Material into the GI generate Slot)

The best regards from The Croque

[Da_elf]

some materials dont emit the same color? which ones? i thought the laws of physics dictate that we see a color because all the other colors are absorbed by the material and that color thats left to reflect back to our eyes is the color we see the object to be. So if that color is reflected back to our eyes, isnt it the color thats reflected onto another surface? the only time it might look like its not that color is when the surface its reflected onto is also colored and the two colors are mixed...or perhaps if the recieving surface is white. maybe there are two colored objects side by side mixing their bounced light..oooor. maybe its a colored light mixing its color with the color of the object. Other than that im not sure how its physically possible for a colored surface to emit any other color than the one we see. Seeing as how thats not a real physical effect you want to recreate why not just fake it with an extra light or something. Unless there is a real physics reason to have it wouldnt it be concidered just another option in the material to clutter it up?

[metroberlin]

Thecoque is rigt. it doesn´t matter if its realistic. i often had the same problem. it would be great to control the colorbounces. like in viz or lightscape. a room with white walls and a strong red floor. it was no problem in lightscape to avoid red walls, but it´s a problem in vray. i know, there a few tricks, but it would be great to control it in the material !!!!!!

[Thecroque]

Hi Da_elf...

You are right with your explanations... my claim was a little bit short and incomplete... I have heard about materials which dosnt emit same colour... but I cant say exactly why and which...

Other example for this technique:
Our brain does correct some Colour-informations which come from the eye... when we know that a wall is white, and the surrounding light is orange, (like on sunset) the wall seems to be white anyhow... but when we take a Picture from this wall, we can see that the wall seems to be orange (or red)
Into a interior scene with a yellow carpet on the floor the walls seems to be white (for a human being) and vray make extreme yellow walls... when I reduce the Generate GI field, light gets lost and the scene isnt right illuminated...

The best regards from The Croque

[metroberlin]

hehe, i think we have posted the same example at the same time

[Da_elf]

well. yeah. we have all asked in the wishlist for something like a bounced light saturation peramiter. that would be usefull per material or per object to be able to lower the color saturation of the bounced light. but im not sure its needed to change the actual color of the bounced light to something else....
...but. i guess if we have a saturation spinner a color swatch override next to it might not clutter things up too much i guess

[losbellos]

well for some special cases you could use the old trick, clone the object and calculate the irradiance with whatever color u want to emit, and then for the render put the original back. At least a solution.

Otherwise I believe this option is included in vray 1.1 . There were so many people asking for it, and I think this "silence" that they didnt put too much attention on it is more than dubious. So...

[Da_elf]

or render with one color yet use something like combustion to change the color

[Yadla]

Sorry I dont have my ftp working, so Thecroque, see ur email,
i send to u the pict u wanted

To have this, its simple:
1- Render the pict with the GI u want, then save ur irradiance map.
2- Change ur materials (in this case, change ur blue wall in a yellow one)
3- Re-render the scene, using the irradiance file of the first rendering
(u can setup this in advanced irr map settings)

u got it

Edit: FTP working, here is the pict:

[flipside]

Yes but it would be nice in one pass no? I also think that a per material spinner for the saturation would be nice. But instead of the spinner just make a color box, that's even better. If you just want to desaturate, just copy the diffuse color in this new color box and reduce the saturation of that color. If you really want more extreme results you could use totally different color in this colorbox. This way everybody is happy

[Yadla]

I DID IT !

in one pass!

now it's the challenge flipside, find how i could do it
PS: the floor and the ball are White material.

[mc-escher]

possible real example

This could be totally off the wall, but wouldn't an iridescent surface
(such as those two color paint jobs) exibit this type of behavior?

In this case, perceived color is based on viewing angle. The ideal diffuse
and directional diffuse components make up one color seen at a point
whereas the ideal specular component makes up a second color seen
at another.

In my mind the color reflected from a surface point is
really goverend by the angle of incident light on the surface. and the
surface material BDRF properties.

An Example: Take a sphere which would show pink when
viewed directly (ideal specular), and green at glancing angles
(directional diffuse + ideal diffuse).

If the only light in the scene was at the viewer
then the normals on the sphere pointing to the user would have pink
color and irradiance on an underlying plane would be green (from ideal
and directional diffuse components only)

If the light was placed under the sphere pointing directly up, the
viewer would see a green sphere but the GI on the groundplane
would be pinkish as it main contributor is the ideal specular.

Taking the thought experiment further, I thought of another scenario.
A laptop screen nearly parallel with the groundplane (face normals
pointed mostly towards the plane)

If the light originates from the viewer, then the screen, at a severe
glancing angle, would appear as though it were a nice gray diffuse
color with light shining on it. but
the screen itself would be adding GI to the plane. below.
This could explain the possible use for a GI map slot

PS: I tried to get a picture of the laptop, but my stupid thinkpad has
nearly a 180 Degree viewing angle =/


someone tell me I'm crazy...
escher