stupid shader question and alpha transparency

[mauchi]

Hi,

I'm not a shader guy, this may be really stupid. I have a texture of a butterfly that gets mapped on wings. I have a ramp in the alpha to make them more transparent over the span of the wing. some of the default shaders respect this, but I am not getting it in the alpha of the render in the mantra render window. Am I missing something?

Would a kind houdini stranger send me back a scene or shader where this actually works?

Thank you!

texture lives here:

http://dl.getdropbox.com/u/1154467/dogfacebutterfly_tangerine.2.tif

[symek]

Cheers,

generally all you need is to multiply alpha from your texture by opacity just before its output in a vop network. Take a look at Decay shader in the attached file. In that particular example though, I had to change additionally decayVOP inside a shader, since it was compositing texture's alpha over surface, assuming surface alpha to be 1. But this is particular case of decay shader (perhaps I should use different material as a example).

Depending on circumstances you could also pipe texture alpha (fourth component of textureVOP), into Af (alpha) slot of vop network output it self. This will overwrite any opacity result in alpha channel.

hth.

skk.

butterfly_ramp.hipnc

Edited August 17, 2009 by SYmek

[mauchi]

that worked!

Thank you!

Cheers,

generally all you need is to multiply alpha from your texture by opacity just before its output in a vop network. Take a look at Decay shader in the attached file. In that particular example though, I had to change additionally decayVOP inside a shader, since it was compositing texture's alpha over surface, assuming surface alpha to be 1. But this is particular case of decay shader (perhaps I should use different material as a example).

Depending on circumstances you could also pipe texture alpha (fourth component of textureVOP), into Af (alpha) slot of vop network output it self. This will overwrite any opacity result in alpha channel.

hth.

skk.