VRayMap Question

[jkletzien]

Hello everyone-

 

I am a new VRay user, and while this is a VRay map question, in the end however I get this effect I would be happy 'cause I could stop beating my head against the wall.

 

I am working on a project that has a similar finish to this image. While I am not sure I believe in essence it is back painted glass, so has all the attributes of glass but also has the color of the paint on the back.

 

The quality that I am most interested in drawing your attention to here, and attaining at some stage is the quality of reflections.

 

Where it reflects something light, the quality of the thing reflected retains much of its color in the reflection, and where it refects something dark the glass becomes more transparent and the color of the underlying paint starts to take on more prominence.

 

It is very similar to a carpaint material, and while I know how I would handle this with a standard material (I would use a mask in the reflection slot, and put a raytrace in both the image and mask slots) when I try to do something similar with the vray map, (or anything with the vray map outside of its basic use as a reflection or refraction mask) it doesn't compute any reflection - and just comes back as a balck result.

 

Other things tried that didn't work for me:

Blend material with VRay Map as blend channel

Shellac Material with shellac material described as above

VRay Map with a color correction upping its contrast

Using a VRay map in the opacity slot

 

So...

 

Question 1. does anyone have any theories as to how they would do this material (so it is renderable in one pass)?

 

Question 2. Is the use of the VRay map really limited to its unadulterated state in the reflection and refraction slots (and how painful is that)?

 

Any help would be appreciated.

 

Thanks-

 

Jon

[kippu]

have you tried egz vray materials..... he has a carpaint material which might help

 

if not ...its a script available at http://www.vray.info ... if u did try it ..sorry for time wasted

[jkletzien]

Kippu-

 

It is a good question, and we did in fact try it. My observations of it was that it has the same limitations that the custom stuff we were working on did, in that using a straight reflection they were of a consistent intensity, (or were varied by the falloff map) and not the value of what was being reflected.

 

Good question though I should have let folks know we did try that.

 

Jon

[Tim Saunders]

Well it looks fully opaque, so I would just use a falloff map with vray map in the bottom slot, and adjust the top color as needed.

[Clifton Santiago]

Forget about the Vray map. Use a Vray material (as in Vray 1.47.03)

 

For example, how I would get the blue opaque glass in the photo you posted:

 

1) In the Diffuse color, set the desired color, in this case a shade of blue.

 

2) Make the Reflection color white. Enable Fresnel reflections. Unlock the Fresnel IOR by clicking the "L" button. Adjust the reflection strength by changing the fresnel IOR value. For glass like in the photo, I would use about 3.2.

 

I really don't think the blue glass is anywhere near as complex as automotive paint, and I think this should work fine. This of course assumes you have a quality environment map. For best quality reflections use a high-quality HDRI map in the reflection environment slot.

[jkletzien]

You're right it isn't as complex because the underlying blue material is significantly flatter than the metallic flecked paint used in cars. But it does retain the quality of having two levels of stuff - a specular material outside (turtle wax/glass)and a more matte material underneath (metallic paint/paint).

 

And having tried vray materials with the qualities you describe (diffuse color, fresnel active, falloff, etc...) it doesn't respond like I see this respond, or how I understand glass to respond.

 

If you window shop on a sunny day you have to get up to the glass and get your face close enough so you can see through your own dark reflection. This has nothing to do with fresnel but with the opacity and transparency of a bright reflection vs a dark one. In this case I want it to be dark/transparent so I can see to the red/green/blue underneath. This is where it is similar to carpaint.

 

Some of this seems to come through in a basic VRay material, but not enough to suit my tastes, so I would like to amplify this, and I was hoping that the employ of a Vray map in an opacity slot, or a mask slot, or a blend slot could help - as I know of no other way (real or implied) to reintroduce the reflection as a map.

 

So while I appreciate your thoughts, I am pretty disappointed that the VRay map is so predetermined in its use, and that VRay doesn't allow for individual users to push these opacity variables (like it does in the ability to push the fresnel variables).

 

C'est la vie

[Ismael]

From Viz 4 help:

 

"Each standard light's Multiplier is multiplied by the Physical Scale value to give a light intensity value in candelas. For example, with the default Physical Scale of 1500, a standard omni light is treated by the renderer and radiosity as a photometric isotropic light of 1500 candelas. Physical Scale is also factored into reflections, refractions, and self-illumination."

"General Guidelines for Physical Scale Values:

If you only use Photometric lights, IES Sun, and IES Sky , set the Physical Scale value to the equivalent of the brightest light source in the scene. This will set the appropriate conversion scale for reflections, self-illumination, and all other non-physically based elements a VIZ material offers.

If you use Standard lights and Texture Sky , the Physical Scale value acts as a conversion scale the radiosity engine needs to calculate energy. However, if you use the Affect Indirect Only flagLogarithmic_Exposure_Control, you don't need to worry about the physical scale."

 

Note that Viz uses (Max too), Exposure Control to map reflections properly.

What that tries to accomplish are things as you mentioned: "Where it reflects something light, the quality of the thing reflected retains much of its color in the reflection, and where it refects something dark the glass becomes more transparent and the color of the underlying paint starts to take on more prominence."

Another name for Exposure Control I equate with Light Mapping. A reflection is nothing more than light on an object being bounced off another (in this case glass) and arriving at our eyes or another light capturing device like a camera. On the subject of Clear Glass, reflections will be only as strong as the difference in incident light on the reflected object Vs the incident light directly on objects behind the glass. That is the reason why in Daylight, I can see part of my neighborhood reflected on my house windows and at night that reflection fades and I can see clearly the interior of my house when the lights are on and the shades are not drawn. Lighter colors "transport" light more that darker colors; so it is that reflections or not, a lighter object seems brighter (as if self illuminated) more than darker objects next to them with the same incident illumination on them.

Vray or Max or any other good rendering engine can be made to render totally believable "real" scenes or objects. In the end, there may never be a magic shader that reads the mind of the artist adjusts all required parameters and renders a personal vision. For now, just look around and also "see" what others have seen, like http://www.neilblevins.com/cg_education/cg_education.htm

You will reproduce that material and many more because you are inquiring deeply; and you will know, understand and implement.

 

Cheers,

 

Ismael

[jkletzien]

"You will reproduce that material and many more because you are inquiring deeply; and you will know, understand and implement."

 

You dropping the compliment 'cause you really think so, or are you the guy responsible for the utter uselessness of the VRay Map and want to get on my good side ?

 

In all seriousness, thanks. Hopefully I can find a beautiful work around and get the kind of results I am hoping for - which may or may not be physically accurate but ultimately is at the heart of expression.