[Sidefx-houdini-list] Rayhit returning wierd normal
andy at andynicholas.com
Sat Oct 11 12:42:33 EDT 2008
Great, thanks guys. Pablo, some good suggestions, I'll give those a go.
I'll try triangulating them too, thanks Simon. I'll let you know how it
> I have shaders which do similar things and work fine, i have noticed
> though that you can get lots of misses if the geometry isn't triangles,
> but that's the only problems I've had.
> -----Original Message-----
> From: sidefx-houdini-list-bounces at sidefx.com on behalf of Andy Nicholas
> Sent: Fri 10/10/2008 23:59
> To: sidefx-houdini-list at sidefx.com; andy at andynicholas.com
> Subject: Re: [Sidefx-houdini-list] Rayhit returning wierd normal
> Hmmm, didn't manage to figure this out. It's a really odd one.
> Just to explain what I'm trying to do. I need to do a "wet map". So I was
> trying to put together a shader that could detect if its surface was
> inside another object (the liquid) or not.
> The way I was going to do this was to fire a ray in the direction of the
> surface normal. If I don't hit anything, I shade the surface white. If I
> hit something and it's normal faces towards me, then I also shade it white
> (since I must be outside that surface). If I hit something and the normal
> is facing away, then I must be inside the surface, so I need to shade it
> The idea is that I can then use "mantra -u" (or the render parameter
> equivalent) to bake it into a texture to use as a wet map later.
> Should be simple huh? The problem is that the RayHit VOP is returning me a
> load of rubbish in the hit normal output, hence making this shader
> impossible to write. Does anyone have any ideas how I can get this to
> work, or what I'm doing wrong?
> I have some possible workarounds using totally different methods, but I
> really want to know why I can't make what seems like a trivially easy
> Appreciate any help you can give,
>> Just a quick question... has anyone had any issues with the VEX shader
>> node "rayhit" returning utter rubbish in the output normal? I'm getting
>> whole load of moire like noise patterns being returned (I've made sure
>> there's no intersecting geometry).
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