problem computing ... (solved)

OpenGL OpenGL: Advanced Coding
1

Hello,
I’m using framebuffer object to render-to-texture, and i use it as texture to make water reflection effect.
If i use the texture without projection, the texture is ok, the scene is rendered to texture well. But i can’t use projection on to it.

Any idea or correction could be helpfully.

scrfeenshot: http://delfin.klte.hu/~fazekaim/water3.jpg

my water shaders:

    public static String waterVertexShader =
            "void main(void)
" +
            "{
" +
            "  gl_Position = ftransform();
" +
            "  gl_TexCoord[0] = gl_TextureMatrix[0] * gl_Vertex;
" +
            "}";

    public static String waterFragmentShader =
            "uniform sampler2D reflection;
" +
            "void main (void)
" +
            "{
" +
            "  gl_FragColor = texture2DProj(reflection,gl_TexCoord[0]);
" +
            "  gl_FragColor.a = 1.0;
" +
            "}";

my water rendering code:

private void EnableWaterTextureMatrix(){
        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.glMatrixMode( GL.GL_TEXTURE );
        gl.glLoadIdentity();
        gl.glScalef(0.5f, 0.5f, 1.0f);
        gl.glTranslatef(1.0f, 1.0f, 0.0f);
        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 waterrender() {

        EnableWaterTextureMatrix();

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

        

        activateTexture( 0, FBOTexture[0], GL.GL_TEXTURE_2D );
        
        gl.glUseProgramObjectARB( waterShaderObj[0] );

            gl.glUniform1iARB( waterReflection[0], 0 );
            

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

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

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

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

        gl.glUseProgramObjectARB( 0 );

        deactivateTexture( 0, GL.GL_TEXTURE_2D );

        DisableWaterTextureMatrix();
    }
2

Try setting the translation vector for your water texture matrix to 0.5, 0.5, 0. You want to project from the center of the texture, not the edge.

3

Thanks, i tried it, but nothing has changed.
I tried to use more vertexes (1024 and not 4) in the water plane, without better result.

4

It is working…

I had to change these statements: from
gl.glMultMatrixf( projectionlMatrix );
gl.glMultMatrixf( modelMatrix );
to this:
gl.glMultMatrixf( modelMatrix );
gl.glMultMatrixf( projectionlMatrix );

Oh, i’m so stupid. :slight_smile: