Use of FBO and Shader causing positioning issues

advanced
#1

Hello,
I noticed a positioning issue today when working with an FBO and Shader. I’m simply calling ofDrawCircle(ofGetMouseX(), ofGetMouseY(),radius) into and FBO then into a Shader. The X axis will be correct but the Y axis is reversed. However, when I std::cout << mouseX << mouseY I get the correct Y mouse information. So then I went on the check just drawing the FBO itself and found that the Y axis was correct! Now, I checked writing the shader over the FBO and noticed the Y axis reversal. My shader.vert is as follows:

#version 120

void main()
{
gl_Position = ftransform();
}

I’m not a shader expert so I’m curious am I doing something incorrectly to the positioning by calling fftransform?

Thanks for any help!

#2

Hi there!

Can you show us how are allocating your FBO?

Also, are you using any camera?

#3

In Setup()

   fbo.allocate(ofGetWidth(), ofGetHeight(), GL_RGBA);
    
    fbo.begin();
    ofClear(0);
    fbo.end();

In Draw()

  fbo.begin();
     ofClear(0);
    ofSetColor(ofColor::red);
    ofDrawCircle(ofGetMouseX(), ofGetMouseY(), 50);
    fbo.end();

    shader.begin();
    shader.setUniformTexture("iChannel0", fbo, 0);
    ofRect(0,0, ofGetWidth(), ofGetHeight());
    shader.end();
#4

Ok so the fix I found was to call:

ofSetOrientation(OF_ORIENTATION_DEFAULT,false);

Referenced from another OF Forum entry