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.. py:currentmodule:: moderngl
One familiar triangle
=====================
As with any graphics library guide, we also have a guide on how to draw a triangle.
Below is a slightly modified line drawing code from the :doc:`previous tutorial <../first_rendering/rendering>`. The following code draws one triangle:
.. rubric:: Entire source
.. literalinclude:: triangle_draw.py
:emphasize-lines: 35-41, 43, 51
:linenos:
When you run the code you will see this:
.. figure:: triangle.png
:alt: Triangle
:align: center
:figclass: align-center
Triangle
As you may have noticed, we only specified three colors for each vertex, but OpenGL interpolates our triangle and we see a soft transition of colors.
At this point you can try out the fragment shader, for example, let's draw a lighting effect:
.. rubric:: Fragment shader
.. literalinclude:: lighted.frag.glsl
:language: glsl
:emphasize-lines: 8-9
.. figure:: lighted_triangle.png
:alt: Lighted triangle
:align: center
:figclass: align-center
Lighted triangle
Shaders are not very fond of branching algorithms and operations such as ``if (condition) {action} else {action}``. It is recommended to use formulas more often.
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