Py API Docs: New custom shader example
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doc/python_api/examples/gpu.11.py
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61
doc/python_api/examples/gpu.11.py
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"""
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Custom Shader for dotted 3D Line
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--------------------------------
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In this example the arc length (distance to the first point on the line) is calculated in every vertex.
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Between the vertex and fragment shader that value is automatically interpolated for all points that will be visible on the screen.
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In the fragment shader the `sin` of the arc length is calculated.
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Based on the result a decision is made on whether the fragment should be drawn or not.
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"""
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import bpy
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import gpu
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from random import random
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from mathutils import Vector
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from gpu_extras.batch import batch_for_shader
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vertex_shader = '''
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uniform mat4 u_ViewProjectionMatrix;
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in vec3 position;
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in float arcLength;
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out float v_ArcLength;
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void main()
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{
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v_ArcLength = arcLength;
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gl_Position = u_ViewProjectionMatrix * vec4(position, 1.0f);
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}
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'''
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fragment_shader = '''
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uniform float u_Scale;
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in float v_ArcLength;
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void main()
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{
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if (step(sin(v_ArcLength * u_Scale), 0.5) == 1) discard;
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gl_FragColor = vec4(1.0);
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}
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'''
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coords = [Vector((random(), random(), random())) * 5 for _ in range(5)]
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arc_lengths = [0]
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for a, b in zip(coords[:-1], coords[1:]):
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arc_lengths.append(arc_lengths[-1] + (a - b).length)
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shader = gpu.types.GPUShader(vertex_shader, fragment_shader)
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batch = batch_for_shader(shader, 'LINE_STRIP',
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{"position" : coords,
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"arcLength" : arc_lengths})
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def draw():
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shader.bind()
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matrix = bpy.context.region_data.perspective_matrix
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shader.uniform_float("u_ViewProjectionMatrix", matrix)
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shader.uniform_float("u_Scale", 10)
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batch.draw(shader)
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bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_VIEW')
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