Rudinie Posted November 4, 2008 Share Posted November 4, 2008 I know this issue has been asked like a 100 times, but allthough i've read pretty much all of the answers and followed all the tutorials (3dBuzz, DigitalTutors, the MiguelPerez-tutorial) i could find i still don't understand how to control the alpha of sprites . (yeah, you can call me stupid from this point on) What i've got in the attached file is a sphere emiting particles and in de popnet after the source a color and a sprite sop. The color sop is supposed to ramp up the alpha base on $LIFE. In the Obj level i assigned a sprite-material to the particle-emiter in the material tab. This sprite-material i made myself in SHOP. In the sprite-material i've got a VOP VEX Surface SHOP and a Mantra_Sprite Procedural wired respectivelly into the surface shader and the Geometry Shader of the suboutput. The VOP VEX Surface SHOP's output has got a Surface Opacity (Of) (vector) and a surface Alpha (Af) (float). How does this work, why opacity and alpha, what's the difference? What do i need to edit to get control over the opacity or alpha if you will of my sprites? I could really use some pointers to set up the most basic way to control and understand sprites before i even try to go further and make something that actually looks nice as well. Any help very much apreciated. Cheers, Rudi smoke_test.hipnc Quote Link to comment Share on other sites More sharing options...
Rudinie Posted November 5, 2008 Author Share Posted November 5, 2008 I found out that even the example posted in: http://forums.odforce.net/index.php?showtopic=7826 did not result in alpha's in my sprites, but rather sprites with the houdini non-commercial logo in each sprite. After re-installing Houdini the problems went away and i am now finally able to see transparancy in my sprites. I would still however love to understand the relation between alpha and opacity a little better so if anyone has a link or a tip it would be more then welcome. Tnx Rudi Quote Link to comment Share on other sites More sharing options...
Allegro Posted November 5, 2008 Share Posted November 5, 2008 I found out that even the example posted in: http://forums.odforce.net/index.php?showtopic=7826 did not result in alpha's in my sprites, but rather sprites with the houdini non-commercial logo in each sprite. After re-installing Houdini the problems went away and i am now finally able to see transparancy in my sprites. I would still however love to understand the relation between alpha and opacity a little better so if anyone has a link or a tip it would be more then welcome. Tnx Rudi Opacity is the ability for a material to be transparent or opaque. Generally, you want to premultiply your color by your opacity for this to render accurately. The alpha however works like a matte in your render where whatever value this has, your final image will have when rendering. So if you give your material A an opacity of 0, objects that appear behind material A in your render will still render and appear in your alpha channel. If however you give material A an alpha of 0, your alpha channel in your render will have a value of 0 wherever that materail exists. Quote Link to comment Share on other sites More sharing options...
Allegro Posted November 5, 2008 Share Posted November 5, 2008 Here is an altered version of your material. Feel free to ask questions if you have any. sprite_test.tar.gz Quote Link to comment Share on other sites More sharing options...
Rudinie Posted November 6, 2008 Author Share Posted November 6, 2008 Wow, this is really kind, thanks a lot! I will study your modifications and probably learn a lot. Thanks again! Rudi Quote Link to comment Share on other sites More sharing options...
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