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life_compute.glsl
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life_compute.glsl
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#[compute]
#version 450
layout(local_size_x = 4, local_size_y = 4) in;
// Set & bindings to match those defined in GDScript.
layout(set = 0, binding = 0, std430) restrict buffer FloatBufferIn {
float data[];
}
buffer_in;
layout(set = 0, binding = 1, std430) restrict buffer FloatBufferOut {
float data[];
}
buffer_out;
layout(set = 0, binding = 2, std430) restrict buffer SizeDataBuffer {
int width;
int height;
}
size_data;
void get_neighbours_lazy(out int[8] neighbour_indices, in int index) {
// Return the eight neighbour indices of the given index.
// Don't worry about whether the indices are out of bounds.
neighbour_indices = int[8]( \
index - 1 - size_data.width, index - size_data.width, index + 1 - size_data.width, \
index - 1, index + 1, \
index - 1 + size_data.width, index + size_data.width, index + 1 + size_data.width);
}
void main() {
// Use gl_GlobalInvocationID to get the array index for this invocation.
// Offset by 1 in each direction to allow lazy finding of neighbour indices.
int index = int((gl_GlobalInvocationID.x + 1) + (gl_GlobalInvocationID.y + 1) * size_data.width);
int[8] neighbour_indices;
neighbour_indices = int[8](-1, -1, -1, -1, -1, -1, -1, -1);
get_neighbours_lazy(neighbour_indices, index);
// Calculate number of living neighbours.
float neighbour_life = 0.0;
neighbour_life += buffer_in.data[neighbour_indices[0]];
neighbour_life += buffer_in.data[neighbour_indices[1]];
neighbour_life += buffer_in.data[neighbour_indices[2]];
neighbour_life += buffer_in.data[neighbour_indices[3]];
neighbour_life += buffer_in.data[neighbour_indices[4]];
neighbour_life += buffer_in.data[neighbour_indices[5]];
neighbour_life += buffer_in.data[neighbour_indices[6]];
neighbour_life += buffer_in.data[neighbour_indices[7]];
// Cell comes to life with exactly three living neighbours. Stays alive with two or three living neighbours.
// Write new state to output buffer.
buffer_out.data[index] = float((neighbour_life == 2.0)) * buffer_in.data[index] + float((neighbour_life == 3.0)) * 1.0;
}