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"""
Compute shader renders a 32 x 32 grid to a 512, 512 texture
"""
import moderngl as mgl
from _example import Example
from moderngl_window import geometry
class RenderTextureCompute(Example):
title = "Render Texture Using Compute Shader"
gl_version = (4, 3)
aspect_ratio = 1.0
def __init__(self, **kwargs):
super().__init__(**kwargs)
# reference compute shader: http://wili.cc/blog/opengl-cs.html
self.compute = self.ctx.compute_shader('''
#version 430
layout (local_size_x = 16, local_size_y = 16) in;
// match the input texture format!
layout(rgba8, location=0) writeonly uniform image2D destTex;
uniform float time;
void main() {
// texel coordinate we are writing to
ivec2 texelPos = ivec2(gl_GlobalInvocationID.xy);
// Calculate 1.0 - distance from the center in each work group
float local = 1.0 - length(vec2(ivec2(gl_LocalInvocationID.xy) - 8) / 8.0);
// Wave covering the screen diagonally
float global = sin(float(gl_WorkGroupID.x + gl_WorkGroupID.y) * 0.1 + time) / 2.0 + 0.5;
imageStore(
destTex,
texelPos,
vec4(
local,
global,
0.0,
1.0
)
);
}
''')
self.compute['destTex'] = 0
# For rendering a simple textured quad
self.quad_program = self.ctx.program(
vertex_shader="""
#version 330
in vec3 in_position;
in vec2 in_texcoord_0;
out vec2 uv;
void main() {
gl_Position = vec4(in_position, 1.0);
uv = in_texcoord_0;
}
""",
fragment_shader="""
#version 330
uniform sampler2D texture0;
out vec4 fragColor;
in vec2 uv;
void main() {
fragColor = texture(texture0, uv);
}
""",
)
# RGB_8 texture
self.texture = self.ctx.texture((256, 256), 4)
self.texture.filter = mgl.NEAREST, mgl.NEAREST
self.quad_fs = geometry.quad_fs()
def render(self, time, frame_time):
self.ctx.clear(0.3, 0.3, 0.3)
w, h = self.texture.size
gw, gh = 16, 16
nx, ny, nz = int(w/gw), int(h/gh), 1
try:
self.compute['time'] = time
except Exception:
pass
# Automatically binds as a GL_R32F / r32f (read from the texture)
self.texture.bind_to_image(0, read=False, write=True)
self.compute.run(nx, ny, nz)
# Render texture
self.texture.use(location=0)
self.quad_fs.render(self.quad_program)
if __name__ == '__main__':
RenderTextureCompute.run()
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