Re: [osg-users] Layer Opacity using TexEnvCombine
Hi Jason, You're exactly right, if texture 1 has transparency, then I want texture 0 to show through no matter what. Doing something like the following on unit 0 works great in that case, but I also want to add in another scaling factor that will scale the alpha value of the texture from 0 to 1 to essentially act as a slider for the opacity. I'll keep hacking along, but I might need to just stick with shaders. osg::TexEnvCombine* tec = new osg::TexEnvCombine; tec-setSource0_RGB(osg::TexEnvCombine::TEXTURE1); tec-setOperand0_RGB(osg::TexEnvCombine::SRC_COLOR); tec-setSource1_RGB(osg::TexEnvCombine::TEXTURE0); tec-setOperand1_RGB(osg::TexEnvCombine::SRC_COLOR); tec-setSource2_RGB(osg::TexEnvCombine::TEXTURE1); tec-setOperand2_RGB(osg::TexEnvCombine::SRC_ALPHA); tec-setCombine_RGB(osg::TexEnvCombine::INTERPOLATE); csn-getOrCreateStateSet()-setTextureAttribute(0, tec); Thanks! Jason On Mon, Jun 8, 2009 at 8:23 PM, Jason Daly jd...@ist.ucf.edu wrote: Jason Beverage wrote: Hi all, I'm trying to figure out a way to modify layer opacity using TexEnvCombine that takes into account the underlying alpha channel of a texture. Do you mean if unit 1's texture has transparency, you want that to show through to unit 0's texture? The osgFX::MultiTextureControl does very close to what I'm looking to do, but doesn't take into account the fact that the underlying texture may contain transparency (like a road overlay). From my understanding of texenvcombine, I can either use a constant color or SRC_ALPHA as an operand, but not a combination of both. It sounds like you need three parameters combined (2 texture colors and a user-defined parameter), so your only hope is the INTERPOLATE mode for the alpha values (INTERPOLATE is the only combiner operation that takes three parameters). Try this: tec-setSource0_RGB(osg::TexEnvCombine::TEXTURE0); tec-setSource1_RGB(osg::TexEnvCombine::TEXTURE1); tec-setCombine_RGB(osg::TexEnvCombine::MODULATE); tec-setConstantColor(osg::Vec4(1.0, 1.0, 1.0, userDefinedAlpha)); tec-setSource0_Alpha(osg::TexEnvCombine::TEXTURE0); tec-setSource1_Alpha(osg::TexEnvCombine::TEXTURE1); tec-setSource2_Alpha(osg::TexEnvCombine::CONSTANT); tec-setCombine_Alpha(osg::TexEnvCombine::INTERPOLATE); I just made this up, so I have no idea if it will work or not. It might not be the only possibility, either, but it's all I can think of right now. --J ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Layer Opacity using TexEnvCombine
Jason Beverage wrote: Hi Jason, You're exactly right, if texture 1 has transparency, then I want texture 0 to show through no matter what. Doing something like the following on unit 0 works great in that case, but I also want to add in another scaling factor that will scale the alpha value of the texture from 0 to 1 to essentially act as a slider for the opacity. I'll keep hacking along, but I might need to just stick with shaders. Yeah, at first I thought i had an easy answer to your question, but as I looked into it I realized just how many combinations you can come up with for TexEnvCombine settings. I just sent you my best guess, which is probably way off. Let me know if you figure it out... --J ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
[osg-users] Layer Opacity using TexEnvCombine
Hi all, I'm trying to figure out a way to modify layer opacity using TexEnvCombine that takes into account the underlying alpha channel of a texture. The osgFX::MultiTextureControl does very close to what I'm looking to do, but doesn't take into account the fact that the underlying texture may contain transparency (like a road overlay). From my understanding of texenvcombine, I can either use a constant color or SRC_ALPHA as an operand, but not a combination of both. I really want a way to use SRC_ALPHA scaled by some user defined opacity value (0 to 1). Does anyone know of a way to accomplish this? I know how to accomplish this using a glsl shader, but can't quite figure out how to do it with texenvcombine. Thanks! Jason ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Layer Opacity using TexEnvCombine
Jason Beverage wrote: Hi all, I'm trying to figure out a way to modify layer opacity using TexEnvCombine that takes into account the underlying alpha channel of a texture. Do you mean if unit 1's texture has transparency, you want that to show through to unit 0's texture? The osgFX::MultiTextureControl does very close to what I'm looking to do, but doesn't take into account the fact that the underlying texture may contain transparency (like a road overlay). From my understanding of texenvcombine, I can either use a constant color or SRC_ALPHA as an operand, but not a combination of both. It sounds like you need three parameters combined (2 texture colors and a user-defined parameter), so your only hope is the INTERPOLATE mode for the alpha values (INTERPOLATE is the only combiner operation that takes three parameters). Try this: tec-setSource0_RGB(osg::TexEnvCombine::TEXTURE0); tec-setSource1_RGB(osg::TexEnvCombine::TEXTURE1); tec-setCombine_RGB(osg::TexEnvCombine::MODULATE); tec-setConstantColor(osg::Vec4(1.0, 1.0, 1.0, userDefinedAlpha)); tec-setSource0_Alpha(osg::TexEnvCombine::TEXTURE0); tec-setSource1_Alpha(osg::TexEnvCombine::TEXTURE1); tec-setSource2_Alpha(osg::TexEnvCombine::CONSTANT); tec-setCombine_Alpha(osg::TexEnvCombine::INTERPOLATE); I just made this up, so I have no idea if it will work or not. It might not be the only possibility, either, but it's all I can think of right now. --J ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
