
.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/gloo/hello_fbo.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_gallery_gloo_hello_fbo.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_gloo_hello_fbo.py:


Use FrameBuffers
================

Minimal example demonstrating the use of frame buffer objects (FBO).
This example blurs the output image.

.. GENERATED FROM PYTHON SOURCE LINES 12-125



.. image-sg:: /gallery/gloo/images/sphx_glr_hello_fbo_001.png
   :alt: hello fbo
   :srcset: /gallery/gloo/images/sphx_glr_hello_fbo_001.png
   :class: sphx-glr-single-img





.. code-block:: Python



    from vispy import gloo
    from vispy import app
    import numpy as np

    # Create vertices
    vPosition = np.array([[-0.8, -0.8, 0.0], [+0.7, -0.7, 0.0],
                          [-0.7, +0.7, 0.0], [+0.8, +0.8, 0.0, ]], np.float32)
    vPosition_full = np.array([[-1.0, -1.0, 0.0], [+1.0, -1.0, 0.0],
                               [-1.0, +1.0, 0.0], [+1.0, +1.0, 0.0, ]], np.float32)
    vTexcoord = np.array([[0.0, 0.0], [0.0, 1.0],
                          [1.0, 0.0], [1.0, 1.0]], np.float32)

    # For initial quad
    VERT_SHADER1 = """
    attribute vec3 a_position;
    void main (void) {
        gl_Position = vec4(a_position, 1.0);
    }
    """

    FRAG_SHADER1 = """
    uniform vec4 u_color;
    void main()
    {
        gl_FragColor = u_color;
    }
    """

    # To render the result of the FBO
    VERT_SHADER2 = """
    attribute vec3 a_position;
    attribute vec2 a_texcoord;
    varying vec2 v_texcoord;
    void main (void) {
        // Pass tex coords
        v_texcoord = a_texcoord;
        // Calculate position
        gl_Position = vec4(a_position.x, a_position.y, a_position.z, 1.0);
    }
    """

    FRAG_SHADER2 = """
    uniform sampler2D u_texture1;
    varying vec2 v_texcoord;
    const float c_zero = 0.0;
    const int c_sze = 5;
    void main()
    {
        float scalefactor = 1.0 / float(c_sze * c_sze * 4 + 1);
        gl_FragColor = vec4(c_zero, c_zero, c_zero, 1.0);
        for (int y=-c_sze; y<=c_sze; y++) {
            for (int x=-c_sze; x<=c_sze; x++) {
                vec2 step = vec2(x,y) * 0.01;
                vec3 color = texture2D(u_texture1, v_texcoord.st+step).rgb;
                gl_FragColor.rgb += color * scalefactor;
            }
        }
    }
    """


    SIZE = 50


    class Canvas(app.Canvas):

        def __init__(self):
            app.Canvas.__init__(self, keys='interactive', size=(560, 420))

            # Create texture to render to
            shape = self.physical_size[1], self.physical_size[0]
            self._rendertex = gloo.Texture2D((shape + (3,)))

            # Create FBO, attach the color buffer and depth buffer
            self._fbo = gloo.FrameBuffer(self._rendertex, gloo.RenderBuffer(shape))

            # Create program to render a shape
            self._program1 = gloo.Program(VERT_SHADER1, FRAG_SHADER1)
            self._program1['u_color'] = 0.9, 1.0, 0.4, 1
            self._program1['a_position'] = gloo.VertexBuffer(vPosition)

            # Create program to render FBO result
            self._program2 = gloo.Program(VERT_SHADER2, FRAG_SHADER2)
            self._program2['a_position'] = gloo.VertexBuffer(vPosition)
            self._program2['a_texcoord'] = gloo.VertexBuffer(vTexcoord)
            self._program2['u_texture1'] = self._rendertex

            self.show()

        def on_resize(self, event):
            width, height = event.physical_size
            gloo.set_viewport(0, 0, width, height)

        def on_draw(self, event):
            # Draw the same scene as as in hello_quad.py, but draw it to the FBO
            with self._fbo:
                gloo.set_clear_color((0.0, 0.0, 0.5, 1))
                gloo.clear(color=True, depth=True)
                gloo.set_viewport(0, 0, *self.physical_size)
                self._program1.draw('triangle_strip')

            # Now draw result to a full-screen quad
            # Init
            gloo.set_clear_color('white')
            gloo.clear(color=True, depth=True)
            self._program2.draw('triangle_strip')


    if __name__ == '__main__':
        canvas = Canvas()
        app.run()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.422 seconds)


.. _sphx_glr_download_gallery_gloo_hello_fbo.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: hello_fbo.ipynb <hello_fbo.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: hello_fbo.py <hello_fbo.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: hello_fbo.zip <hello_fbo.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_
