Cats eyes

[Abigor]

Hey all. Anyone have a good rig, or advice on making cats eyes? Im referring specifically to the effect where, when light shines in a cats eyes, their eyes seem to glow very brightly from behind. So, definitely some incidence stuff involved i would think.

I've doodled around with a few ideas, but nothing i would say that looks great yet. Just though I'd see if someone else had some good advice or anything.

Thanks!

[Maxx]

Just a thought - if you target your light to a null and move the null (to aim the light), you can set up a luminosity or color gradient on the cat's irises based on the distance to that null, thereby faking the effect and possibly saving some render time.

I do hope that made sense...

[WilliamVaughan]

James Kimball had a killer setup that he did on one of my character a couple ytears ago....
http://www.jamesstudiogallery.com/

It was the turtle in his 3d gallery:
http://jamesstudiogallery.com/studio/list.shtml?cat=z1096325123.1154391440&index=1154402430_15513&st=

He is an amazing artist and I bet he would share his technique if you shoot him a message!

[Medi8or]

..or you could use nodes.

For my example here:
Item Info nodes are set to camera and light.
Subtract and Normalize nodes finds vectors (direction) from surface to camera and from surface to light.
The Dot node finds cosine of the angle between those to vectors, which means it gives 1 if light and camera is in the same direction.
The gradient node just gives some control to what angles should make the eye glow and how much...

Hope this can help.. :)

[Abigor]

very interesting guys. thanks for the responses! i will try them out today (or soon), and see what i get.

[Medi8or]

Just another method for nodes. Set the surface normal to point towards "camera", and you can use specularity. (works with all lights, not just one you set up in the nodes, like last example...)

[Abigor]

medi, i copied your node setup, but im not getting the kind of result id expect. i just have a very lumious sphere that doesnt seem to change, no matter what angle i put the light on it.

i am tryin the eyeball on its own, outside of the head. does it need head geometry to obscure the light and create the effect?

[Medi8or]

Which node-setup did you try?

Have a look at these scenes, one for each of the node-setups. :)

[Abigor]

Ah, i see. #1 looks promising. Does it only work though when the camera and light are in exactly the same position? Also, will it work for a regular sphere shape? The eyeballs of the character are already modelled and such, so changing them now would cause a few problems :) haha.

[Medi8or]

For the first node-setup, if you drop the Gradient node, and just plug the Dot node into Luminosity, it will gradually start to glow as the light and camera gets closer to eachother. With the Gradient node in the example-scene, it glows only when the angle between Light, surface, and camera is less than about 30 degrees... (when Dot node returns between ~0.85 - 1.0 )

The shape of the surface shouldn't matter. :)

[Abigor]

eyes are coming along nicely! 1 thing i would like to do though. when i look at the eyeballs from the side, i can still see the bright glowing reflective centers. realy, i cant see them from wherever i look at. what i would like, is some sorta function that only makes them visible from bang on infront (give or take a few degrees).

the Dot node seems like it should do the job, but then why isnt it working rite now? so i just need something that can take my results i have no, and limit them.

medi, im using your nodes, but theyr not seeming to work properly :(

[Abigor]

nevermind, i made it work! had to tweak some things. i ended up mixing your nodes medi, with the surfacing i got from James as per Williams post above. Added in a bit of my own stuff and i think i have a pretty neat night-time eyeball! Unfortunatly, Im not allowed to show any renders.

Thanks so much for your help guys!