hello,

i think there is a game of life example in gem example/glsl folder.
this example show how to make a simple feedback.
you don"t need to modifie the rendering, since you juste nead a redback after 
the rendering.
but readback are ineficient.

example 07.framebuffer_and_shader show how to use 2 framebufer in order to use 
1 to render the 2nd one.
this can be use to do efficient motion blur, or whatever shader you want.
but you have to modifie the rendering part : replacing gemhead by abstraction 
that render in the same framebufer.

cheers
c



Le 03/10/2013 02:10, Py Fave a écrit :
Hello list ,

i'm currently trying to understand a bit more glsl ,
and am tearing my hairs

i have a scene with some  moving geometry (torus)
on this  geometry i use successfully a simple shader to plot a moving circle.

Then
i try to make the classical feedback effect , but i need to use glsl
because i want to control precisely the adding of the image at time
and at time+1

here is the feedback shader i try to use .
----
uniform sampler2D tex1,tex2;
uniform float motionblurstrenght;
vec2 coord = gl_TexCoord[0].st;
void main()
{
     vec4 t1 = texture(tex1, coord);//new frame
     vec4 t2 = texture(tex2, coord);//acumulated frame
     gl_FragColor = vec4(t1.r);
    float r = ((1.-motionblurstrenght)*t2.r) + (t1.r);//motion blur
      gl_FragColor = vec4(r);
     }
----------------------


do you have a clean example or hints on how to implement this ?
i am currently fighting  with gemframebuffer and pix_texture
and  rendering order and texunits .
and i feel i'm missing something ..

i would like , if possible to keep this as an effect i can turn on and
off  , without modifing my current gem chains .

i think i need two gem chains ,one early and one at last in the frame
drawing chronology , but i can't make it though i tried a lot

any help appreciated .

Pierre-Yves

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