Have you heard about http://glslsandbox.com%|%glslsandox%|% website ?

It shows (using WebGL) what can be done with pixel shaders. 

There are some really impressive ones ...

Here is a small Tcl script using the tcl3d package that can be used to try the shaders of http://glslsandbox.com%|%glslsandox%|%

You only need to replace the pixel shader code to try another one ...

Hope you'll enjoy !

======
#! /bin/sh
# next line restarts using tclsh \
    exec tclsh85 "$0" ${1+"$@"}

package require tcl3d

proc mkshader {type src} {
    set sh [glCreateShader $type]
    tcl3dOglShaderSource $sh $src
    glCompileShader $sh
    puts "compilation report : [tcl3dOglGetShaderState $sh $::GL_COMPILE_STATUS] [tcl3dOglGetShaderInfoLog $sh]"
    return $sh
}

proc mkprogram {v f} {
    set p [glCreateProgram]
    glAttachShader $p $v
    glAttachShader $p $f
    glLinkProgram $p
    puts "link report : [tcl3dOglGetProgramState $p $::GL_LINK_STATUS] [tcl3dOglGetProgramInfoLog $p]"
    return $p
}

proc createcb { toglwin } {
    glClearColor 0.0 0.0 0.0 0.0
    glShadeModel $::GL_SMOOTH

    set v [mkshader  $::GL_VERTEX_SHADER {
        void main() {
            gl_Position = ftransform();
        }
    }]
    
    # --- replace the code below to try another shader
    set f [mkshader $::GL_FRAGMENT_SHADER {
        #ifdef GL_ES
        precision mediump float;
        #endif

        uniform float time;
        //uniform vec2 mouse;
        //uniform vec2 resolution;

        float lengthsq(vec2 p) { return dot(p, p); }

        float noise(vec2 p){
            return fract(sin(fract(sin(p.x) * (43.13311)) + p.y) * 31.001);
        }


        float worley(vec2 p) {        
          // Initialise distance to a large value
          float d = 20.0;
          for (int xo = -2; xo <= 2; xo++) {
            for (int yo = -2; yo <= 2; yo++) {
              // Test all surrounding cells to see if distance is smaller.
              vec2 test_cell = floor(p) + vec2(xo, yo);
              // Update distance if smaller.
              float n0 = noise(test_cell);
              float n1 = noise(test_cell + vec2(134.0,8413.0));
                                                                                
              float ox = mix( n0, n1, sin(time) );
              float oy = mix( n0, n1, cos(time) );
                                                                                
              vec2 c = test_cell + vec2(ox,oy);
              d = min(d, lengthsq(p - c));
            }
          }
          return d;
        }

        void main() {
            vec2 uv = gl_FragCoord.xy;
            float t = 0.9 * worley(gl_FragCoord.xy / 20.0);
            gl_FragColor = vec4(vec3(t,sqrt(t),t), 1.0);
        }
    }]


    set p [mkprogram $v $f]
    
    glUseProgram $p

    set ::uloc_time       [glGetUniformLocation $p "time"]
    set ::uloc_mouse      [glGetUniformLocation $p "mouse"]
    set ::uloc_resolution [glGetUniformLocation $p "resolution"]
}

proc displaycb { toglwin } {
    incr ::time
    glUniform1f $::uloc_time [expr {0.05*$::time}]
    
    glClear $::GL_COLOR_BUFFER_BIT

    glLoadIdentity
    glBegin GL_QUADS
    glVertex2f -1 -1
    glVertex2f -1  1
    glVertex2f  1  1
    glVertex2f  1  -1
    glEnd
    
    $toglwin swapbuffers
}

proc reshapecb { toglwin { w -1 } { h -1 } } {
    set w [$toglwin width]
    set h [$toglwin height]
    glUniform2f $::uloc_resolution $w $h
    glViewport 0 0 $w $h
}

proc Animate {} {
    .w postredisplay
    set ::animateId [after 40 ::Animate]
}

proc StartAnimation {} {
    puts "starting animation"
    if { ! [info exists ::animateId] } {
        Animate
    }
}

proc StopAnimation {} {
    if { [info exists ::animateId] } {
        after cancel $::animateId 
        unset ::animateId
    }
}


togl .w -w 640 -h 480 -double true -createproc createcb -displayproc displaycb -reshapeproc reshapecb
pack .w -expand 1 -fill both
bind .w <Key-Escape> exit
bind .w <Motion> {
    glUniform2f $::uloc_mouse %x %y
}

wm protocol . WM_DELETE_WINDOW exit
StartAnimation


======

Here are two screenshots made using the above program and 2 different shaders :


[http://img15.hostingpics.net/pics/434638bubbles.png]
[http://img15.hostingpics.net/pics/939312lightning.png]

** See also **

   * [Functional imaging]

<<categories>>Tcl3D | Graphics