Sorry,Mazy.I get zero value for all pixels.The code is :
glBindTexture(GL_TEXTURE_RECTANGLE_NV, fptexture);
glCopyTexSubImage2D(GL_TEXTURE_RECTANGLE_NV, 0,0,0,512,512, 512,512);
glReadPixels(0,512,512,GL_RGBA,GL_FLOAT,data);
add_bias(); //check the value
fpbuffer2.deactivate();
fpbuffer.activate();
glBindProgramARB(GL_FRAGMENT_PROGRAM_NV, simple_sum);
glEnable(GL_FRAGMENT_PROGRAM_NV);
glActiveTextureARB(GL_TEXTURE0_ARB);
glBindTexture(GL_TEXTURE_RECTANGLE_NV, fptexture);
glActiveTextureARB(GL_TEXTURE1_ARB);
glBindTexture(GL_TEXTURE_RECTANGLE_NV, fptexture);
glEnable(GL_TEXTURE_RECTANGLE_NV);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
for(int i=0;i<512;i++)
{
glBegin(GL_QUADS);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, i-1,0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, i,0);
glVertex2f(i,0);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, i-1,0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, i,0);
glVertex2f(i+1,0);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, i,511);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, i+1,511);
glVertex2f(i+1,511);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, i,511);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, i+1,511);
glVertex2f(i,511);
glEnd();
}
glReadPixels(0,0,512,512,GL_RGBA,GL_FLOAT,data);
add_bias(); //check the value
simple_sum:
!!FP1.0
TEX R1,f[TEX0],TEX0,RECT;
TEX R2,f[TEX1],TEX0,RECT;
ADD o[COLR],R1,R2;
END
what is wrong with it?