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

.. only:: html

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

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

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

.. _sphx_glr_gallery_scene_instanced_quad_visual.py:


Custom Visual for instanced rendering of a colored quad
=======================================================

# this example is based on the tutorial: T01_basic_visual.py

.. GENERATED FROM PYTHON SOURCE LINES 12-82







.. code-block:: Python


    from vispy import app, gloo, visuals, scene, use
    import numpy as np

    # full gl+ context is required for instanced rendering
    use(gl='gl+')


    vertex_shader = """
    // both these attributes will be defined on an instance basis (not per vertex)
    attribute vec2 shift;
    attribute vec4 color;

    varying vec4 v_color;
    void main() {
        v_color = color;
        gl_Position = $transform(vec4($position + shift, 0, 1));
    }
    """

    fragment_shader = """
    varying vec4 v_color;

    void main() {
      gl_FragColor = v_color;
    }
    """


    class InstancedRectVisual(visuals.Visual):
        def __init__(self, x, y, w, h):
            visuals.Visual.__init__(self, vertex_shader, fragment_shader)

            # vertices for two triangles forming a rectangle
            self.vbo = gloo.VertexBuffer(np.array([
                [x, y], [x+w, y], [x+w, y+h],
                [x, y], [x+w, y+h], [x, y+h]
            ], dtype=np.float32))

            self.shared_program.vert['position'] = self.vbo
            self._draw_mode = 'triangles'

            # create a vertex buffer with a divisor argument of 1. This means that the
            # attribute value is set to the next element of the array every 1 instance.
            # The length of the array multiplied by the divisor determines the number
            # of instances
            self.shifts = gloo.VertexBuffer(np.random.rand(100, 2).astype(np.float32) * 500, divisor=1)
            self.shared_program['shift'] = self.shifts

            # we can provide additional buffers with different divisors, as long as the
            # amount of instances (length * divisor) is the same. In this case, we will change
            # color every 5 instances
            self.color = gloo.VertexBuffer(np.random.rand(20, 4).astype(np.float32), divisor=5)
            self.shared_program['color'] = self.color

        def _prepare_transforms(self, view):
            view.view_program.vert['transform'] = view.get_transform()


    # create a visual node class to add it to the canvas
    InstancedRect = scene.visuals.create_visual_node(InstancedRectVisual)

    canvas = scene.SceneCanvas(keys='interactive', show=True)

    rect = InstancedRect(0, 0, 20, 40, parent=canvas.scene)

    if __name__ == '__main__':
        import sys
        if sys.flags.interactive != 1:
            app.run()


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

   **Total running time of the script:** (0 minutes 0.044 seconds)


.. _sphx_glr_download_gallery_scene_instanced_quad_visual.py:

.. only:: html

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

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

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

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

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


.. only:: html

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

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