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"""
Instanced rendering without supplying per instance data
doing offsets with gl_InstanceID in vertex shader.
"""
import numpy as np
import moderngl
from _example import Example
class InstancedRendering(Example):
title = "Instanced Rendering"
gl_version = (3, 3)
def __init__(self, **kwargs):
super().__init__(**kwargs)
# gl_InstanceID offsets rotation per instance
self.prog = self.ctx.program(
vertex_shader='''
#version 330
in vec2 in_vert;
in vec4 in_color;
out vec4 v_color;
uniform float Rotation;
uniform vec2 Scale;
void main() {
v_color = in_color;
float r = Rotation * (0.5 + gl_InstanceID * 0.05);
mat2 rot = mat2(cos(r), sin(r), -sin(r), cos(r));
gl_Position = vec4((rot * in_vert) * Scale, 0.0, 1.0);
}
''',
fragment_shader='''
#version 330
in vec4 v_color;
out vec4 f_color;
void main() {
f_color = v_color;
}
''',
)
self.scale = self.prog['Scale']
self.rotation = self.prog['Rotation']
vertices = np.array([
# x, y, red, green, blue, alpha
1.0, 0.0, 1.0, 0.0, 0.0, 0.5,
-0.5, 0.86, 0.0, 1.0, 0.0, 0.5,
-0.5, -0.86, 0.0, 0.0, 1.0, 0.5,
], dtype='f4')
self.vbo = self.ctx.buffer(vertices)
self.vao = self.ctx.vertex_array(
self.prog,
[(self.vbo, '2f 4f', 'in_vert', 'in_color')],
)
def render(self, time, frame_time):
self.ctx.clear(1.0, 1.0, 1.0)
self.ctx.enable(moderngl.BLEND)
self.scale.value = (0.5, self.aspect_ratio * 0.5)
self.rotation.value = time
# For every instanced rendered gl_InstanceID increments by 1
self.vao.render(instances=10)
if __name__ == '__main__':
InstancedRendering.run()
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