
.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/gloo/gl/quad.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_gl_quad.py>`
        to download the full example code.

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

.. _sphx_glr_gallery_gloo_gl_quad.py:


Drawing a simple quad
=====================

.. GENERATED FROM PYTHON SOURCE LINES 13-121







.. code-block:: Python

    import numpy as np

    from vispy import app
    from vispy.gloo import gl

    vertex_code = """
        uniform float scale;
        attribute vec4 color;
        attribute vec2 position;
        varying vec4 v_color;
        void main()
        {
            gl_Position = vec4(scale*position, 0.0, 1.0);
            v_color = color;
        } """

    fragment_code = """
        varying vec4 v_color;
        void main()
        {
            gl_FragColor = v_color;
        } """


    class Canvas(app.Canvas):
        def __init__(self):
            app.Canvas.__init__(self, size=(512, 512), title='Quad (GL)',
                                keys='interactive')

        def on_initialize(self, event):
            # Build data
            self.data = np.zeros(4, [("position", np.float32, 2),
                                     ("color", np.float32, 4)])
            self.data['color'] = [(1, 0, 0, 1), (0, 1, 0, 1),
                                  (0, 0, 1, 1), (1, 1, 0, 1)]
            self.data['position'] = [(-1, -1), (-1, +1),
                                     (+1, -1), (+1, +1)]

            # Build & activate program

            # Request a program and shader slots from GPU
            program = gl.glCreateProgram()
            vertex = gl.glCreateShader(gl.GL_VERTEX_SHADER)
            fragment = gl.glCreateShader(gl.GL_FRAGMENT_SHADER)

            # Set shaders source
            gl.glShaderSource(vertex, vertex_code)
            gl.glShaderSource(fragment, fragment_code)

            # Compile shaders
            gl.glCompileShader(vertex)
            gl.glCompileShader(fragment)

            # Attach shader objects to the program
            gl.glAttachShader(program, vertex)
            gl.glAttachShader(program, fragment)

            # Build program
            gl.glLinkProgram(program)

            # Get rid of shaders (no more needed)
            gl.glDetachShader(program, vertex)
            gl.glDetachShader(program, fragment)

            # Make program the default program
            gl.glUseProgram(program)

            # Build buffer

            # Request a buffer slot from GPU
            buf = gl.glCreateBuffer()

            # Make this buffer the default one
            gl.glBindBuffer(gl.GL_ARRAY_BUFFER, buf)

            # Upload data
            gl.glBufferData(gl.GL_ARRAY_BUFFER, self.data, gl.GL_DYNAMIC_DRAW)

            # Bind attributes
            stride = self.data.strides[0]
            offset = 0
            loc = gl.glGetAttribLocation(program, "position")
            gl.glEnableVertexAttribArray(loc)
            gl.glBindBuffer(gl.GL_ARRAY_BUFFER, buf)
            gl.glVertexAttribPointer(loc, 3, gl.GL_FLOAT, False, stride, offset)

            offset = self.data.dtype["position"].itemsize
            loc = gl.glGetAttribLocation(program, "color")
            gl.glEnableVertexAttribArray(loc)
            gl.glBindBuffer(gl.GL_ARRAY_BUFFER, buf)
            gl.glVertexAttribPointer(loc, 4, gl.GL_FLOAT, False, stride, offset)

            # Bind uniforms
            # --------------------------------------
            loc = gl.glGetUniformLocation(program, "scale")
            gl.glUniform1f(loc, 1.0)

        def on_draw(self, event):
            gl.glClear(gl.GL_COLOR_BUFFER_BIT)
            gl.glDrawArrays(gl.GL_TRIANGLE_STRIP, 0, 4)

        def on_resize(self, event):
            gl.glViewport(0, 0, *event.physical_size)

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


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

   **Total running time of the script:** (0 minutes 0.074 seconds)


.. _sphx_glr_download_gallery_gloo_gl_quad.py:

.. only:: html

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

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

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

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

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

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

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


.. only:: html

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

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