auvi@auv-i.com

When I send video source that has an alpha channel to a jit.gl.videoplane, the "color 1. 1. 1. $1" message will allow me to fade the plane in and out.

However, when I apply a shader to the texture of the videoplane (using "sendtexture" and "shader" messages), it's no longer possible to control fading with the "color" message anymore. 

The effect of the shader is visible, but the "color" message no longer produces a fade.

Perhaps the alpha information is getting lost through the shader? It seems the same for the 5 or 6 different shaders I tried.

However, when I apply a shader to the texture of the videoplane (using "sendtexture" and "shader" messages), it's no longer possible to control fading with the "color" message anymore. 
The effect of the shader is visible, but the "color" message no longer produces a fade.

alpha-and-shaders

ahh so you do have an intel mac, (more incentive to update auvi to UB) hehehehe

Try using a jit.gl.slab to process textures - I can properly control 

alpha via the color message when using slab 'chains', in fact, its 

Some shaders build textures and have their own color controls on the 

jit.gl.shader, so if you need to use a shader, check its params, it 

On Jan 17, 2007, at 5:33 PM, Kurt Ralske wrote:

> When I send video source that has an alpha channel to a 

> jit.gl.videoplane, the "color 1. 1. 1. $1" message will allow me to 

> However, when I apply a shader to the texture of the videoplane 

> (using "sendtexture" and "shader" messages), it's no longer 

> possible to control fading with the "color" message anymore.

> The effect of the shader is visible, but the "color" message no 

> Perhaps the alpha information is getting lost through the shader? 

> It seems the same for the 5 or 6 different shaders I tried.

Try using a jit.gl.slab to process textures - I can properly control  
alpha via the color message when using slab 'chains', in fact, its  
vital for me!

Some shaders build textures and have their own color controls on the  
jit.gl.shader, so if you need to use a shader, check its params, it  
may have a color or alpha param.

>
>
> When I send video source that has an alpha channel to a  
> jit.gl.videoplane, the "color 1. 1. 1. $1" message will allow me to  
> fade the plane in and out.
>
> However, when I apply a shader to the texture of the videoplane  
> (using "sendtexture" and "shader" messages), it's no longer  
> possible to control fading with the "color" message anymore.
> The effect of the shader is visible, but the "color" message no  
> longer produces a fade.
>
> Perhaps the alpha information is getting lost through the shader?  
> It seems the same for the 5 or 6 different shaders I tried.
>
> Max 4.6.2, Intel MacBook Pro
>
> Thanks for your help
> Kurt

On Jan 17, 2007, at 5:37 PM, Nicholas C. Raftis III wrote:

> ahh so you do have an intel mac, (more incentive to update auvi to 

> -=ili!ili=- www.Axiom-Crux.net -=ili!ili=-

>
> ahh so you do have an intel mac, (more incentive to update auvi to  
> UB) hehehehe
>
> :D
>
>
> --
> -=ili!ili=-  www.Axiom-Crux.net  -=ili!ili=-

On Jan 17, 2007, at 2:33 PM, Kurt Ralske wrote:

As you'll notice if you inspect the shader files, most of the video 

processing shaders do not multiply the output gl_FragColor with the 

current gl_Color. They are written with the assumption that they are 

going to be used in a slab-like setting, without using other things 

like lighting and material properties, gl_Color, etc. in the output 

calculation. I assume this is the cause of what you're experiencing.

While you can modify any of the shaders to take this state 

information into account, I think that you'll probably get the 

results you're looking for by sending through jit.gl.slab- 

>jit.gl.videoplane, rather than using jit.gl.videoplane's shader 

attribute. If that doesn't work for whatever reason. I'd recommend 

making a set of shaders that functions the way you need. For more 

info check out the shader based tutorials, and various GLSL resources 

in the cycnling74.com resource guide and online.

The GLSL language specification, Orange Book, and Clockwork coders 

tutorials are probably good places to start.

http://www.opengl.org/documentation/glsl/

http://www.clockworkcoders.com/oglsl/tutorials.html

> When I send video source that has an alpha channel to a  
> jit.gl.videoplane, the "color 1. 1. 1. $1" message will allow me to  
> fade the plane in and out.
>
> However, when I apply a shader to the texture of the videoplane  
> (using "sendtexture" and "shader" messages), it's no longer  
> possible to control fading with the "color" message anymore.
> The effect of the shader is visible, but the "color" message no  
> longer produces a fade.
>
> Perhaps the alpha information is getting lost through the shader?  
> It seems the same for the 5 or 6 different shaders I tried.

As you'll notice if you inspect the shader files, most of the video  
processing shaders do not multiply the output gl_FragColor with the  
current gl_Color. They are written with the assumption that they are  
going to be used in a slab-like setting, without using other things  
like lighting and material properties, gl_Color, etc. in the output  
calculation. I assume this is the cause of what you're experiencing.

While you can modify any of the shaders to take this state  
information into account, I think that you'll probably get the  
results you're looking for by sending through jit.gl.slab- 
 >jit.gl.videoplane, rather than using jit.gl.videoplane's shader  
attribute. If that doesn't work for whatever reason. I'd recommend  
making a set of shaders that functions the way you need. For more  
info check out the shader based tutorials, and various GLSL resources  
in the cycnling74.com resource guide and online.

The GLSL language specification, Orange Book, and Clockwork coders  
tutorials are probably good places to start.
http://www.opengl.org/documentation/glsl/
http://www.3dshaders.com/
http://www.clockworkcoders.com/oglsl/tutorials.html

Shaders use a different GPU pipeline than the fixed function pipeline

everyone is used to and the glColor() uses. Unless a shader

specifically uses the gl_Color parameter, the jit.gl.videoplane @color

attribute will not actually have an effect. Instead, there is usually

some parameter to the shader that sets the alpha of the final color or

you have to set the alpha of the textures being used. As an example,

the compositing shaders use the alpha channels of the 2 input textures

On 1/17/07, Nicholas C. Raftis III wrote:

> ahh so you do have an intel mac, (more incentive to update auvi to UB) hehehehe

Hi Kurt,
Shaders use a different GPU pipeline than the fixed function pipeline
everyone is used to and the glColor() uses.  Unless a shader
specifically uses the gl_Color parameter, the jit.gl.videoplane @color
attribute will not actually have an effect.  Instead, there is usually
some parameter to the shader that sets the alpha of the final color or
you have to set the alpha of the textures being used.  As an example,
the compositing shaders use the alpha channels of the 2 input textures
to write the final alpha value.

On 1/17/07, Nicholas C. Raftis III  wrote:
>
> ahh so you do have an intel mac, (more incentive to update auvi to UB) hehehehe
>
> :D
>
>
> --
> -=ili!ili=-  www.Axiom-Crux.net  -=ili!ili=-
>


Alpha and shaders