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#[compute]
#version 450
#VERSION_DEFINES
layout(local_size_x = 64, local_size_y = 1, local_size_z = 1) in;
#define PARTICLE_FLAG_ACTIVE uint(1)
#define PARTICLE_FLAG_STARTED uint(2)
#define PARTICLE_FLAG_TRAILED uint(4)
struct ParticleData {
mat4 xform;
vec3 velocity;
uint flags;
vec4 color;
vec4 custom;
};
layout(set = 0, binding = 1, std430) restrict readonly buffer Particles {
ParticleData data[];
}
particles;
layout(set = 0, binding = 2, std430) restrict writeonly buffer Transforms {
vec4 data[];
}
instances;
#ifdef USE_SORT_BUFFER
layout(set = 1, binding = 0, std430) restrict buffer SortBuffer {
vec2 data[];
}
sort_buffer;
#endif // USE_SORT_BUFFER
layout(set = 2, binding = 0, std430) restrict readonly buffer TrailBindPoses {
mat4 data[];
}
trail_bind_poses;
layout(push_constant, binding = 0, std430) uniform Params {
vec3 sort_direction;
uint total_particles;
uint trail_size;
uint trail_total;
float frame_delta;
float frame_remainder;
vec3 align_up;
uint align_mode;
bool order_by_lifetime;
uint lifetime_split;
bool lifetime_reverse;
uint pad;
}
params;
#define TRANSFORM_ALIGN_DISABLED 0
#define TRANSFORM_ALIGN_Z_BILLBOARD 1
#define TRANSFORM_ALIGN_Y_TO_VELOCITY 2
#define TRANSFORM_ALIGN_Z_BILLBOARD_Y_TO_VELOCITY 3
void main() {
#ifdef MODE_FILL_SORT_BUFFER
uint particle = gl_GlobalInvocationID.x;
if (particle >= params.total_particles) {
return; //discard
}
uint src_particle = particle;
if (params.trail_size > 1) {
src_particle = src_particle * params.trail_size + params.trail_size / 2; //use trail center for sorting
}
sort_buffer.data[particle].x = dot(params.sort_direction, particles.data[src_particle].xform[3].xyz);
sort_buffer.data[particle].y = float(particle);
#endif
#ifdef MODE_FILL_INSTANCES
uint particle = gl_GlobalInvocationID.x;
if (particle >= params.total_particles) {
return; //discard
}
#ifdef USE_SORT_BUFFER
if (params.trail_size > 1) {
particle = uint(sort_buffer.data[particle / params.trail_size].y) + (particle % params.trail_size);
} else {
particle = uint(sort_buffer.data[particle].y); //use index from sort buffer
}
#else
if (params.order_by_lifetime) {
if (params.trail_size > 1) {
uint limit = (params.total_particles / params.trail_size) - params.lifetime_split;
uint base_index = particle / params.trail_size;
uint base_offset = particle % params.trail_size;
if (params.lifetime_reverse) {
base_index = (params.total_particles / params.trail_size) - base_index - 1;
}
if (base_index < limit) {
base_index = params.lifetime_split + base_index;
} else {
base_index -= limit;
}
particle = base_index * params.trail_size + base_offset;
} else {
uint limit = params.total_particles - params.lifetime_split;
if (params.lifetime_reverse) {
particle = params.total_particles - particle - 1;
}
if (particle < limit) {
particle = params.lifetime_split + particle;
} else {
particle -= limit;
}
}
}
#endif // USE_SORT_BUFFER
mat4 txform;
if (bool(particles.data[particle].flags & PARTICLE_FLAG_ACTIVE) || bool(particles.data[particle].flags & PARTICLE_FLAG_TRAILED)) {
txform = particles.data[particle].xform;
if (params.trail_size > 1) {
// Since the steps don't fit precisely in the history frames, must do a tiny bit of
// interpolation to get them close to their intended location.
uint part_ofs = particle % params.trail_size;
float natural_ofs = fract((float(part_ofs) / float(params.trail_size)) * float(params.trail_total)) * params.frame_delta;
txform[3].xyz -= particles.data[particle].velocity * natural_ofs;
}
switch (params.align_mode) {
case TRANSFORM_ALIGN_DISABLED: {
} break; //nothing
case TRANSFORM_ALIGN_Z_BILLBOARD: {
mat3 local = mat3(normalize(cross(params.align_up, params.sort_direction)), params.align_up, params.sort_direction);
local = local * mat3(txform);
txform[0].xyz = local[0];
txform[1].xyz = local[1];
txform[2].xyz = local[2];
} break;
case TRANSFORM_ALIGN_Y_TO_VELOCITY: {
vec3 v = particles.data[particle].velocity;
float s = (length(txform[0]) + length(txform[1]) + length(txform[2])) / 3.0;
if (length(v) > 0.0) {
txform[1].xyz = normalize(v);
} else {
txform[1].xyz = normalize(txform[1].xyz);
}
txform[0].xyz = normalize(cross(txform[1].xyz, txform[2].xyz));
txform[2].xyz = vec3(0.0, 0.0, 1.0) * s;
txform[0].xyz *= s;
txform[1].xyz *= s;
} break;
case TRANSFORM_ALIGN_Z_BILLBOARD_Y_TO_VELOCITY: {
vec3 v = particles.data[particle].velocity;
vec3 sv = v - params.sort_direction * dot(params.sort_direction, v); //screen velocity
float s = (length(txform[0]) + length(txform[1]) + length(txform[2])) / 3.0;
if (length(sv) == 0) {
sv = params.align_up;
}
sv = normalize(sv);
txform[0].xyz = normalize(cross(sv, params.sort_direction)) * s;
txform[1].xyz = sv * s;
txform[2].xyz = params.sort_direction * s;
} break;
}
txform[3].xyz += particles.data[particle].velocity * params.frame_remainder;
if (params.trail_size > 1) {
uint part_ofs = particle % params.trail_size;
txform = txform * trail_bind_poses.data[part_ofs];
}
txform = transpose(txform);
} else {
txform = mat4(vec4(0.0), vec4(0.0), vec4(0.0), vec4(0.0)); //zero scale, becomes invisible
}
#ifdef MODE_2D
uint write_offset = gl_GlobalInvocationID.x * (2 + 1 + 1); //xform + color + custom
instances.data[write_offset + 0] = txform[0];
instances.data[write_offset + 1] = txform[1];
instances.data[write_offset + 2] = particles.data[particle].color;
instances.data[write_offset + 3] = particles.data[particle].custom;
#else
uint write_offset = gl_GlobalInvocationID.x * (3 + 1 + 1); //xform + color + custom
instances.data[write_offset + 0] = txform[0];
instances.data[write_offset + 1] = txform[1];
instances.data[write_offset + 2] = txform[2];
instances.data[write_offset + 3] = particles.data[particle].color;
instances.data[write_offset + 4] = particles.data[particle].custom;
#endif //MODE_2D
#endif
}
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