problem using fbo, please HELP

OpenGL OpenGL: Advanced Coding
1

Hello!

I’m tryin to use FBO.
I created an FBO instance with an GL_TEXTURE_2D texture attached to GL_COLOR_ATTACHMENT0_EXT.
When I use like this:

 gl.glBindFramebufferEXT( GL.GL_FRAMEBUFFER_EXT, FBO[0] );
        //gl.glPushMatrix();
            //gl.glScalef( 1.0f, -1.0f, 1.0f );
            render();
        //gl.glPopMatrix();

        gl.glBindFramebufferEXT( GL.GL_FRAMEBUFFER_EXT, 0 );
        render();

After calling the first time the render method the fbo texture is a black.
What do I make wrong?
(sorry, for the bad english)

Thanks…

fbo creation method:

public static void createNewFrameBuffer(int width, int height, int[] FBO, int[] FBORenderBuffer, int[] FBOTexture ){

        gl.glGenFramebuffersEXT( 1, FBO  );
        gl.glBindFramebufferEXT( GL.GL_FRAMEBUFFER_EXT, FBO[0] );

        gl.glGenTextures( 1, FBOTexture );
        //gl.glBindFramebufferEXT( GL.GL_FRAMEBUFFER_EXT, FBOTexture[0] );
        gl.glBindTexture( GL.GL_TEXTURE_2D, FBOTexture[0] );
        gl.glTexImage2D( GL.GL_TEXTURE_2D, 0, GL.GL_RGBA, width, height, 0, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, BufferUtils.bufferOffset(0) );
        gl.glTexParameteri( GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MIN_FILTER, GL.GL_NEAREST );
        gl.glTexParameteri( GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MAG_FILTER, GL.GL_NEAREST );  
        gl.glFramebufferTexture2DEXT( GL.GL_FRAMEBUFFER_EXT, GL.GL_COLOR_ATTACHMENT0_EXT, GL.GL_TEXTURE_2D, FBOTexture[0], 0 );

        gl.glGenRenderbuffersEXT( 1, FBORenderBuffer );
        gl.glBindRenderbufferEXT( GL.GL_RENDERBUFFER_EXT, FBORenderBuffer[0] );
        gl.glRenderbufferStorageEXT( GL.GL_RENDERBUFFER_EXT, GL.GL_DEPTH_COMPONENT24, width, height );
        gl.glFramebufferRenderbufferEXT( GL.GL_FRAMEBUFFER_EXT, GL.GL_DEPTH_ATTACHMENT_EXT, GL.GL_RENDERBUFFER_EXT, FBORenderBuffer[0] );

        if( !checkFrameBufferStatus( width, height ) ){
            JOptionPane.showMessageDialog(null, "FBO jajjajj", "Unavailable extension", JOptionPane.ERROR_MESSAGE);
            System.exit( -1 );
        }

        gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, 0);
    }
private static boolean checkFrameBufferStatus(int width, int height) {
        int status = gl.glCheckFramebufferStatusEXT( GL.GL_FRAMEBUFFER_EXT );
        switch(status) {
            case GL.GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENTS_EXT:
                log( "Framebuffer status = GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT" +status);
                return false;
            case GL.GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT:
                log( "Framebuffer status = GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT" +status);
                return false;
            case GL.GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT:
                log( "Framebuffer status = GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT" +status);
                return false;
            case GL.GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:
                log( "Framebuffer status = GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT" +status);
                return false;
            case GL.GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:
                log( "Framebuffer status = GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT"+status);
                return false;
            case GL.GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:
                log( "Framebuffer status = GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT"+status);
                return false;
            case GL.GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:
                log( "Framebuffer status = GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT" );
                return false;
            case GL.GL_FRAMEBUFFER_COMPLETE_EXT:
                log( "Successfully created the frame buffer object < " +
                    width + ", " + height + ">" );
                return true;
            case GL.GL_FRAMEBUFFER_UNSUPPORTED_EXT:
                log("Failed to create the frame buffer object, please verify your format");
                return false;
            default:
                log("????? FBO ????????");
                return false;
        }
}
2

hi

i had a problem when using GL_TEXTURE_2D,
so i had to use GL_TEXTURE_RECTANGLE_NV instead

this example worked for me ( under linux with a nvidia-card)
http://openvidia.sourceforge.net/fbo.shtml

i hope this will help

3

Hi!
I had the same problem and solved it this way:
I just generated fbos in the init step (glGen…)
I did NOT attached the fbo to an texture there.
(You can do so, but it won’t change a thing in this solution)
When drawing to the FBO I attached the texture :
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FBO);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, Tex,0);

That worked for me. And using GL_TEXTURE_2D is okay.
Hope that helped

4

Thanks.

I’m using a texture with the size of the screen (1024x768) and not a power of 2.
And it is working now with GL_TEXTURE_2D.

I can’t set the coordinate for reflectiong my objects.
my code:

public void display(GLDrawable glDrawable) {
{
gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT );
gl.glMatrixMode(GL.GL_MODELVIEW);
gl.glLoadIdentity();
glu.gluLookAt( eye.x, eye.y, eye.z, focus.x, focus.y, focus.z, up.x, up.y, up.z );

gl.glBindFramebufferEXT( GL.GL_FRAMEBUFFER_EXT, FBO[0] );
            gl.glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
            gl.glClear( GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
            gl.glPushMatrix();
                gl.glScalef( 1.0f, -1.0f, 1.0f );
                renderScene();
            gl.glPopMatrix();

            gl.glBindFramebufferEXT( GL.GL_FRAMEBUFFER_EXT, 0 );
            gl.glClearColor(0.0f, 1.0f, 0.0f, 0.0f);
            gl.glClear( GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT );
            gl.glPushMatrix();
                renderscene();
                renderWater();
            gl.glPopMatrix(); 
}

private void EnableWaterTextureMatrix(){
        gl.glMatrixMode( GL.GL_TEXTURE );

        gl.glScalef(0.5f, 0.5f, 1.0f);
        gl.glTranslatef(1.0f, 1.0f, 0.0f);
        float[] modelMatrix = new float[16];gl.glGetFloatv(GL.GL_MODELVIEW_MATRIX, modelMatrix);
        float[] projectionlMatrix = new float[16];gl.glGetFloatv(GL.GL_PROJECTION_MATRIX, projectionlMatrix);
        gl.glMultMatrixf( modelMatrix );
        gl.glMultMatrixf( projectionlMatrix );

        gl.glMatrixMode( GL.GL_MODELVIEW );
    }

    private void DisableWaterTextureMatrix() {
        gl.glMatrixMode( GL.GL_TEXTURE );
        gl.glLoadIdentity();
        gl.glMatrixMode( GL.GL_MODELVIEW );
    }

public void renderWater() {

        EnableWaterTextureMatrix();

        gl.glEnable( GL.GL_DEPTH_TEST);
        gl.glEnable(GL.GL_MULTISAMPLE_ARB);

        gl.glActiveTextureARB( GL.GL_TEXTURE0_ARB + 0);
        gl.glBindTexture( GL.GL_TEXTURE_2D, FBOTexture[0]);
        gl.glClientActiveTextureARB( GL.GL_TEXTURE0_ARB + 0);
        gl.glEnable( GL.GL_TEXTURE_2D);

            gl.glBegin( GL.GL_QUADS);
                gl.glMultiTexCoord2f( 0, 1, 1 );
                gl.glVertex3f( vertexes[0][0], waterLevel, vertexes[0][1] );

                gl.glMultiTexCoord2f( 0, 1 , 0 );
                gl.glVertex3f( vertexes[1][0], waterLevel, vertexes[1][1] );

                gl.glMultiTexCoord2f( 0, 0, 0 );
                gl.glVertex3f( vertexes[2][0], waterLevel, vertexes[2][1] );

                gl.glMultiTexCoord2f( 0, 0, 1 );
                gl.glVertex3f( vertexes[3][0], waterLevel, vertexes[3][1] );
            gl.glEnd();

        gl.glActiveTextureARB( GL.GL_TEXTURE0_ARB + 0);
        gl.glDisable( GL.GL_TEXTURE_2D);
        gl.glClientActiveTextureARB( GL.GL_TEXTURE0_ARB + 0);

        gl.glDisable( GL.GL_BLEND );

        DisableWaterTextureMatrix();

    }

It renders well the water plane with the fbo texture, but I don’t know how to compute reflection texture coordinates.