Creating a realistic looking headlight lens?

[AC5L4T3R]

For what seems an eternity now I've tried to recreate the image below but so far I've not even got close.

In my scene I have a vray disc light to mimic the light coming from the Xenon bulb, but I cannot for the life of me get it to reflect/refract on the actual lens itself.

Is there anyone who can shed some light (ho ho) on how to get this to happen like the real world?

[piotrus3333]

you need to model at least some of the geometry of the reflector.

[AC5L4T3R]

you need to model at least some of the geometry of the reflector.

This is just an isolated lens, even with the full light enclosure (it's CAD), nothing changes.

[Oleg_Budeanu]

You should model not only the lens itself but the environment. 90% of those reflections are from environment/HDRI

[super gnu]

a couple of observations/questions..

to start simple, do you see the light through the lens if you have the headlight cover removed? if i understand correctly, you have a disc light with a hemispherical lens in front of it, with the headlamp cover in front of that? i guess the disc light is larger than the lens, which is why you can see it around the edge as a ring?

did you check you have sufficient bounce depth in your reflections/ refractions? youll need a big number to deal with all the layers transparent material..

is the model clean and closed geometry?

id imagine at the least you would see the light object through the lens if the above answers are yes.

in any case youll need a) a dust coat on the glass to pick up the light properly as in your example
b) youll need caustics to deal with the beam shape. -render on gpu with gi caustics enabled..

[super gnu]

You should model not only the lens itself but the environment. 90% of those reflections are from environment/HDRI

normally i would agree, but looking at the example there appears to be very little environment reflection.. its all reflections of the lens and the indicator light..

[AC5L4T3R]

Guess I wasn't clear enough but super gnu seems to have got it.

The lens geometry does not reflect the vray light the same way as the lens in real life reflects and disperses in the light from the Xenon. In the picture on the left you can see a slight halo where the light is interacting with the imperfections on the lens such as scratches and dust.

My question is how to achieve that effect and what do I need to do in the Vray material to achieve it.

[AC5L4T3R]

a couple of observations/questions..

to start simple, do you see the light through the lens if you have the headlight cover removed? if i understand correctly, you have a disc light with a hemispherical lens in front of it, with the headlamp cover in front of that? i guess the disc light is larger than the lens, which is why you can see it around the edge as a ring?

did you check you have sufficient bounce depth in your reflections/ refractions? youll need a big number to deal with all the layers transparent material..

is the model clean and closed geometry?

id imagine at the least you would see the light object through the lens if the above answers are yes.

in any case youll need a) a dust coat on the glass to pick up the light properly as in your example
b) youll need caustics to deal with the beam shape. -render on gpu with gi caustics enabled..

Sorry, I've just realised that you're talking about the Xenon lens and I'm talking about the headlight cover (which also gets called a lens_

[Buck]

Guess I wasn't clear enough but super gnu seems to have got it.

The lens geometry does not reflect the vray light the same way as the lens in real life reflects and disperses in the light from the Xenon. In the picture on the left you can see a slight halo where the light is interacting with the imperfections on the lens such as scratches and dust.

My question is how to achieve that effect and what do I need to do in the Vray material to achieve it.

it's been a while since Ive done any car renders, but I remember kissing in a layer of glossy reflection to all the chrome elements, and glossy reflection & refraction to all the glass elements, and sometimes sometimes a bit of SSS on the lens directly in front of the bulb and the bulb glass itself, to help it "glow" a bit near the bulb filament. All that helps the light and reflections bounce around more. And then crank the number of traces up, I remember having to use 30 or sometimes more.

If you just have pure reflection and pure refraction with no glossiness at all, you won't get near as much detail.

[super gnu]

Sorry, I've just realised that you're talking about the Xenon lens and I'm talking about the headlight cover (which also gets called a lens_

well same thing in both cases, lens or..lens...

in any case, i would play with vray blend material, have a coat material with less than 100% refraction (could be totally solid i guess, youd have to experiment) white, no reflections. then use a dust mask bitmap to blend it over your glass shader at a tiny percentage. i would guess that would help in picking up where the light hits the lens. if it doesnt work you could maybe try a vray2sided as the coat material, since that will definitely illuminate when hit from behind by a light source.

[kosso_olli]

Is this the result you want to achieve? The layer of dirt and debris on the headlight cover?
https://forums.chaosgroup.com/fileda...7&d=1530872155

[AC5L4T3R]

Yes pretty much, although more subtle like this https://i.pinimg.com/originals/e6/98...5a97f0b3b9.jpg

I dont know why, but I never thought of using a blend for a layer of dirt on glass.. despite me using it for pretty much every material I make.. I'll try it.

[kosso_olli]

Yeah, I exaggerated the effect a bit, since it is a racecar. The effect was indeed done using a blend material, with a smudgy and dusty texture blended over the headlight cover.

[gadzooks]

Is the light source double sided?

[dgruwier]

I think I have a good setup for this:
Start by blending between between a two glass materials, one that is clear, and one one that is going to be your grime layer. For the grime material, start with diffuse, reflection and refraction color set to white.

- Lowering the refraction strength/amount of the grime material gives you some illumination right where the light shines through the lens, as the white diffuse catches the light. That's great for mimicking a buildup of lime and salt and small particles on the lens, that seems to be the primary effect you're going for.
- Lowering the glossiness of refraction+reflection gives you a halo around the light source itself as seen directly through the lens. That's better for mimicking scratches/nicks and greasy smudges on the glass.
- Control the overall strength of the effect with the blend amount, I usually have that set fairly low, it doesn't take a lot.

Use texture maps to drive the various values (Shameless plug). This setup should give you pretty realistic results that hold up when viewed and lit from any angle. Takes some dialing in, but it's the best method I've found.