[Sidefx-houdini-list] edge falloff for shader

Gary Jaeger gary at corestudio.com
Wed Nov 22 08:25:17 EST 2017


Thanks a lot Jeff, Glowy object thing, yes. Not even necessary for it to be a light, actually. In the v-ray/maya way we’d just use a lightshader since it was very fast to calculate.

But I don’t see any attached file? Not sure the list allows that. Got a link? 

Gary Jaeger / 650.728.7957 direct / 415.518.1419 mobile
http://corestudio.com <http://corestudio.com/>

> On Nov 13, 2017, at 3:30 PM, Jeff Wagner <jeff at SIDEFX.COM> wrote:
> 
> You can use the Alpha Mix VOP which is equivalent to facing ratio as well. It's the same thing as that referenced network.
> 
> Alpha roll sets the blending ration between parallel and perpendicular input vectors compared to the current surface shading normal.
> 
> Alpha Para and Alpha Perp set the roll-off between parallel and perpendicular rays.
> 
> You can use the Alpha Mix VOP to calculate your facing ratio.
> 
> I do apologize for the VOP name but we were using this back in the mid 90's to do puffy cloudy stuff with particles rendered as spheres and you mix Alpha based on the I eye ray and the surface normal. Alpha Para sets the parallel strength and Alpha Perp sets strength perpendicular to the surface normal. So I called it Alpha Mix VOP... In hindsight it should be called Facing Ratio VOP... Please submit the RFE if you will to have it renamed or duplicated.
> 
> 
> See the attached file for a workup for an emissive object using a Geo Light for efficiency. I presume you want to set up a glowy objecty thingy based on your question.
> 
> 
> -jeff
> 
> 
> On 2017-11-13 3:16 PM, Alvaro Castaneda wrote:
>> you can calculate your own facing ratio using this method
>> http://houdini.dreamerzstudio.net/?page_id=123
>> 
>> On Tue, Oct 31, 2017 at 2:36 PM, Gary Jaeger <gary at corestudio.com> wrote:
>> 
>>> This one should be so easy. Coming from maya, with the facing ratio for
>>> shaders. In my head it goes like: edge falloff, invert, pipe that into
>>> opacity for a shader that has Emission on. So I get just a bit of emission
>>> as the faces fall away from the camera. But I’ve been connecting things
>>> left and right, but can’t get it to work.
>>> 
>>> Any help?
>>> 
>>> Gary Jaeger / 650.728.7957 direct / 415.518.1419 mobile
>>> http://corestudio.com <http://corestudio.com/>
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