How do you get intense glowy specular highlights? (car paint reflecting sunlight)


#1

Hello all! The pre-installed car paint shaders are freaking awesome! There’s not much I would really change about them, but I’m having difficulty getting those super bright specular highlights that you see in the real world when you look at cars during daytime.

Maybe I’m using the glow render effect incorrectly? But for a “physically correct” highlight, that can cause lens artifacts because of its concentrated intensity, I… don’t know how to do it… would it involve caustics for the camera lenses? Is that even a thing aside from chromatic aberration? :slight_smile:


#2

Just slap it on in AE/PS. Duplicate the image, make an ultra high contrast version which only shows the highlights, then blur the crap out of it and slap it over the top.


#3

the pinging glow that you get around specular highlights when you shoot for real is a result of super bright light reflecting off the crystals of silver in the film stock itself. this means the effects is all down to the film you use and nothing to do with the lens or camera you use.

in 3d it is rare for the renderer to take this kind of effect into account so as mash mentioned it is usually faked using an extra layer you tweak in comp.

cheers, simon w.


#4

Are we talking blooming here? A photo example would be handy to see the effect you want.

That’s interesting, I’ve never heard of this before. I always assumed bloom and highlight was simulating a real world lens effect (Airy disc etc).


#5

it all depends on the optical effect you are trying to re-create.

halation is specifically a glow around specular highlights caused by reflections in the film but there can also be losses of contrast around bright areas caused by reflections within the lens (according to how well the lens is made and the coatings applied to the lenses) but these would be considered lens flare effects.

you then get into glows around lights caused by atmospheric effects like dust, mist and fog.

we already have built in methods for dealing with most of the flare/glare effects occurring outside and inside the lens but nothing that deals with aberrations within the sensor/film.

cheers, simon w.


#6

This is all very good information. That’s fascinating how the silver crystals within film have their own reflective artifacts! Mash, I took your advice, as usual, and I’m getting much closer to the results I’m looking for.

I rendered it as a 32 bit EXR, then duplicated the layer, crunched the levels toward the top of the histogram, selected the whites, deleted everything else, and then set it to screen, did a gaussian blur, and got the result you see below. (I’m thinking I should have done a multipass and only modified the specular layer…)

I had to “stoop” to using a lens flare on the rear fender to get the effect looking right… I like the look of it, but I imagine it’s gonna require some rotoscoping to work in an animation.

Do you know of any other methods aside from the lens flare filter in PS to achieve this type of effect on the rear fender? Gaussian blurs work great but they don’t yield the rays of light you get with a lens flare. :slight_smile:

Any other C&C is welcomed too :slight_smile:


#7

cinema has an extremely powerful (but clumsily laid out) lens flare editor. you can get some very nice effects out of it once you get your head around how it works. in your case you can take advantage of the fact that it splits out a flare into glows and reflexes - switch off the reflex part and you end up with glows only.

obviously this won’t work well for animated scenes as you would have to animate the 3d position of the flare and render it out and it wouldn’t follow the specular unless you had animate it exactly to match.

for a 3rd party solution i believe you should look at video co-pilot optical flares. it should allow you to track a glow in 2d in adobe after effects. it looks quite powerful if you need organic looking glares and flares.

cheers, simon w.


#8

The “Blur a high contrast copy of the image” method is just a really quick and dirty option. A more refined version is, as you’ve done there, render to 32bit and that will give you more refined control over the high contrast intermediate.

The mix modes can give you different effects, If youre trying to drop the image contrast to simulate lens imperfections, then leave the mix mode set to normal and just drop the opacity. To get glows on highlights, blur it less and try the add mode instead.

In- app options, the glow post effect is slow as sludge, but not terrible. Just drop the luminosity setting, as this tends to overcook things. Alternatively, c4d’s highlights filter is essentially a lensflare for reflections. It isnt great, but it can work. If im feeling super lazy then Ill just stick a light on the surface of the object and set it to make a lensflare. Filthy inaccurate hack but it works for stills.


#9

Thanks again for the guidance! :slight_smile: Since this is going to be animated, I think the most efficient way I can get animated specular flares would be to:

  1. Render the frames as is
  2. Do another pass, but change the material of the chrome to one with the only active channel is the specular set to a ridiculous intensity, like 5000%
  3. Make the width of the specular peak realllly tiny -make everything except the car body and the primary light invisible to the renderer.
  4. Render it again… and the only thing that should appear is a few white dots on a black bg
  5. In after effects, do a motion track on the tiny dots, and then link the tracked position to a lens flare filter.
  6. Keyframe the intensity of the flares accordingly
  7. Eat cake and realize such details will hardly matter when the whole thing is motion blurred…
  8. Start all over and just keyframe and tween lens flares manually in after effects :slight_smile:

I need to remember that “good enough” is “good enough” especially when CG is only a tool for story telling… and the editing is going too fast for people to notice anything…

Thanks for the help guys :slight_smile: Now to figure out the most effective way to link the cars velocity and steering to the rotation of the wheels… does anyone know if the drive plug-in is capable of simulating a car drifting (oversteering) around a corner? Everyone seems to like the Drive plug-in… Something tells me I’m best off animating the cars the old fashioned way and replaying it over and over to get it just right…

Has anyone ever animated a race scene? :slight_smile:

I don’t have access to a quadcopter with a stabilized camera, so I’m gonna have to rely on recreating the setting with projection mapping, so I can do crazy camera tricks. :slight_smile: Definitely biting off more than I can chew.


#10

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