Shaders on Raspberry Pi

Natanael Mojica wrote:

hello:
I'm new in openframeworks and GLSL too.
in my program I use shaders to run on the Raspberry Pi"s GPU.., .. but I run that, I get the following error:

indent preformatted text by 4 spaces [warning] ofShader: GL_FRAGMENT_SHADER shader reports:
Compiled
indent preformatted text by 4 spaces[Error] ofShader: checkProgramLinkStatus (): program failed to link
indent preformatted text by 4 spaces[Error] ofShader: program reports:
indent preformatted text by 4 spacesERROR: SEMANTIC-26 (fragment shader, line 9) Illegal field selector (eg using .z with a vec2)

and still have not found the problem in the code,
here the fragment and vertex shader program,, and the ofApp.cpp .:

/ vertex shader

attribute vec4 position;                // set automatically by OF
attribute vec4 normal;                  // set automatically by OF
attribute vec2 texcoord;                // set automatically by OF

uniform mat4 modelViewMatrix;   // set automatically by OF
uniform mat4 projectionMatrix;  // set automatically by OF
uniform float time;

void main(){
        vec4 pos = projectionMatrix * modelViewMatrix * position;
        gl_Position = pos;
}

Fragment shader (error in this shader when it runs)

precision highp float;
uniform sampler2D texture0;
uniform float time;

void main(){
        //Getting the coordinates of the current pixel in texture
        vec2 pos = gl_FragColor[0].st;
        float displacementHeight = 5.0;
        //Changing pos by sinewave
        float displacementY = sin(time + (pos.x / 350.0)) * displacementHeight;
         //Shifting x-coordinate

        //Getting pixel color from texture tex0 in position pos
        vec2 modifiedPosition = pos;
        modifiedPosition.y += displacementY;
        vec4 color = texture2D(texture0, modifiedPosition);
        //Output of shader
        gl_FragColor = color;
    }

with the src code (ofApp.cpp, etc it compile fine)

void ofApp::draw(){
        //Draw background video
        ofBackground(0);
        ofSetColor( 255, 255, 255 );
        float time = ofGetElapsedTimef();
        float duration = (9*n) / 1.0; // al fin de cuentas es una duracion en segundos, uniforme
        float pos = fmodf( time, duration );
        int i = int( pos / duration * n );
        ofImage img = seq[i];
    fbo.begin();
        ofBackground(0);
        ofSetColor(255,255,255);
        img.draw( 0, 0 );
    fbo.end();

    // Ahora el Shader
    shader.begin();
          shader.setUniform1f("time", ofGetElapsedTimef());
          ofSetColor(255,255,255);
          fbo.draw(0,0);
    shader.end();

}

I pass to the shader a rectangle texture, and with the fragment shader I take de color in gl.FragCoor.0, an wok with that using trigonometric function..the effect is like a air waving a flag.. in my Desk computer, the program is perfect, but, that use openGL 2.0, and the Pi uses openGL ES, so I rewrote the code using the variables described in openGL ES. but not work yet

Thanks in advance,
best regards

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