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#ifndef __GLITTER_INC
#define __GLITTER_INC
#include "math.cginc"
#include "pema99.cginc"
#include "quilez.cginc"
struct GlitterParams {
float4 color;
float2 uv_channel;
uint layers;
float cell_size;
float size;
float major_minor_ratio;
float angle_randomization_range;
float center_randomization_range;
float size_randomization_range;
float existence_chance;
#if defined(_GLITTER_ANGLE_LIMIT)
float angle_limit;
float angle_limit_transition_width;
#endif
#if defined(_GLITTER_MASK)
float mask;
#endif
};
static const float2 glitter_offset_vectors[6] = {
float2(0.0, 1.0), // 0 degrees
float2(0.866025, 0.5), // 60 degrees
float2(0.866025, -0.5), // 120 degrees
float2(0.0, -1.0), // 180 degrees
float2(-0.866025, -0.5), // 240 degrees
float2(-0.866025, 0.5) // 300 degrees
};
float4 getGlitter(v2f i, GlitterParams params, float3 normal) {
float c_acc = 0;
[loop]
for (uint layer_i = 0; layer_i < params.layers; layer_i++) {
float2 uv = get_uv_by_channel(i, params.uv_channel);
float2 p = uv + glitter_offset_vectors[layer_i] * params.cell_size * 0.5;
float3 cell_id = float3(floor(p / params.cell_size), layer_i);
float cell_rand = rand3(cell_id*.0001);
float cell_rand2 = rand3((cell_id+1)*.0001);
p = glsl_mod(p, params.cell_size);
p -= params.cell_size * 0.5;
// Apply center randomization
p.x += (cell_rand * 2 - 1) * params.center_randomization_range * (params.cell_size * (1 - params.size)) * 0.5;
// Apply angle randomization
float2x2 p_rot = float2x2(
cos(cell_rand * TAU * params.angle_randomization_range), -sin(cell_rand * TAU * params.angle_randomization_range),
sin(cell_rand * TAU * params.angle_randomization_range), cos(cell_rand * TAU * params.angle_randomization_range)
);
p = mul(p_rot, p);
// Draw ellipses
// First arg is position to evaluate distance at. We project onto z=0.
// Second arg is the size of the ellipse. We set z to cell size because I
// think setting it to 0 would probably create fucked up curvature.
float3 size = float3(params.size * float2(params.major_minor_ratio, 1) * params.cell_size * 0.5, params.cell_size);
// Apply size randomization
size *= (1 - cell_rand * params.size_randomization_range);
// TODO find a good 2d ellipse sdf
float d = distance_from_ellipsoid(float3(p, 0), size);
// TODO antialias using fwidth
float c = (d < 0) * params.color.a;
c *= (cell_rand2 < params.existence_chance);
c_acc = c + (1 - c) * c_acc;
}
#if defined(_GLITTER_ANGLE_LIMIT)
float VdotN = dot(-normalize(i.eyeVec.xyz), normal);
float angle_mask = smoothstep(
cos(params.angle_limit * PI),
cos(params.angle_limit * (1 - params.angle_limit_transition_width) * PI),
VdotN);
c_acc *= angle_mask;
#endif
#if defined(_GLITTER_MASK)
c_acc *= params.mask;
#endif
return float4(params.color.rgb, c_acc);
}
#endif // __GLITTER_INC
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