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jimmyb

Area lights in Houdini?

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Hello,

Does anyone know if there is any way to create an area light in Houdini.

Perhaps a script or something that might be out there. It seems weird

that there is no such feature even in versoin 5.5. Perhaps in 6?

Area lights would look great with specular reflections (shiny car paint

surfaces).

thanks

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Yup, SESI has confirmed that there are area lights in version 6.

stu

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Wha? I know for sure there are area lights in Houdini.

I haven't opened Houdini in a while, but if I remember right this is how you do it:

Go into the shops panel and place a blurshadow shop, now go back into your light object's properties and somewhere you will be able to point to the blurshadow shop. now when you render with vmantra it will have area-light shadows. Go back into the blurshadow shop to adjust softness.

God I'm rusty :blink:

edit------------

do you guys maybe mean some other kind of area lights? Am I just dumb?

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yeah the blurred shadow is part of it, but that doesn't produce

the realistic physical attributes of soft boxes (i.e. Area Lights).

But, if Houdini implements area lights in V6 that would be really

sweet!

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Ohh, you mean a spot light that produces area shadows but also gives correctly shaped specular highlights.

The only soft that I know already has this is Brazil R/S, it would indeed be cool if Houdini supports this in the next version.

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ok another question for you guys. I've been using the vex blur Shadow shop

for a while, but it's very very slow. Comparing it to maya's raytraced shadows

and XSI's, Houdini's is quiet slow.

Is there a way to optimize the render times with that shadow shop - there probobly is. I'm just not sure how.

Any help would be super!!! :D

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Ohh, you mean a spot light that produces area shadows but also gives correctly shaped  specular highlights.

The only soft that I know already has this is Brazil R/S, it would indeed be cool if Houdini supports this in the next version.

I use the light array technique for simulating area lights all the time. A standard part of my setup is a grid object (usually a grid but I've used disks as well, depending on what I'm trying to do) parented to the central light in my array with a scale approximating the area simulated by the array. You can create expression dependencies so that scaling the grid object affects the spacing of the lights in your array if you want to get fancy.

I'll apply a constant shader or shader based on the constant shader with RGB values in the tens or hundreds to this grid. That way I get a more realistic reflection of my light source(s) on other objects in the scene. In most cases it will be necessary to also set SPECULAR values on all other surface shaders to 0, 0, 0 and rely on the reflectivity term alone.

I do this is because specular() (and phong, etc.) are hacks to account for the fact that most CGI lights have no surface area (we've been lighting with really fancy LEDs all these years). Now that I'm actually modelling my light sources all "specular" calculations which take seperate parameters from "reflection" calculations are not only redundant but meaningless and now very visually incorrect.

Though I'm sure they didn't mean to, the founding fathers of CGI helped to foster the notion that "specularity" and "reflectivity" were two seperate surface properties. Even in a well respected, fairly contemporary application like Steve Worley's Gaffer this distinction is maintained due to limitations in rendering rather than an actual representation of real surface properties.

I've seen very little, if any, effort in most 3D applications to educate their users as to why they're given both a "specular" term and "reflection" term. As a result it's easy to struggle to get them to balance out and play well together. Ideally you would just have one parameter unless you were simulating metallic paints and multilayered reflections (like wax over clearcoat over car paint, or pretty much any surface with a varnish or polish). And even then you would have seperate reflection terms with controls for how they relate to each other...not specular() or phong().

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