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#extension GL_ARB_gpu_shader5 : enable
#ifdef GL_ARB_gpu_shader5
#define USE_INVOC_EXT
#endif
#ifdef DOUBLE_MANIFOLD
# ifdef USE_INVOC_EXT
# define invoc_len 2
# else
# define vert_len 8
# endif
#else
# ifdef USE_INVOC_EXT
# define invoc_len 1
# else
# define vert_len 4
# endif
#endif
#ifdef USE_INVOC_EXT
layout(lines_adjacency, invocations = invoc_len) in;
layout(triangle_strip, max_vertices = 4) out;
#else
layout(lines_adjacency) in;
layout(triangle_strip, max_vertices = vert_len) out;
#endif
uniform vec3 lightDirection = vec3(0.57, 0.57, -0.57);
in VertexData {
vec3 pos; /* local position */
vec4 frontPosition; /* final ndc position */
vec4 backPosition;
} vData[];
#define DEGENERATE_THRESHOLD 1e-12
#define len_sqr(a) dot(a, a)
void extrude_edge(bool invert)
{
/* Reverse order if backfacing the light. */
ivec2 idx = (invert) ? ivec2(1, 2) : ivec2(2, 1);
gl_Position = vData[idx.x].frontPosition; EmitVertex();
gl_Position = vData[idx.y].frontPosition; EmitVertex();
gl_Position = vData[idx.x].backPosition; EmitVertex();
gl_Position = vData[idx.y].backPosition; EmitVertex();
EndPrimitive();
}
void main()
{
vec3 v10 = vData[0].pos - vData[1].pos;
vec3 v12 = vData[2].pos - vData[1].pos;
vec3 v13 = vData[3].pos - vData[1].pos;
vec3 n1 = cross(v12, v10);
vec3 n2 = cross(v13, v12);
#ifdef DEGENERATE_THRESHOLD
/* Check if area is null */
vec2 faces_area = vec2(len_sqr(n1), len_sqr(n2));
bvec2 degen_faces = lessThan(abs(faces_area), vec2(DEGENERATE_THRESHOLD));
/* Both triangles are degenerate, abort. */
if (all(degen_faces)) {
return;
}
#endif
vec2 facing = vec2(dot(n1, lightDirection),
dot(n2, lightDirection));
/* WATCH: maybe unpredictable in some cases. */
bool is_manifold = any(notEqual(vData[0].pos, vData[3].pos));
bvec2 backface = greaterThan(facing, vec2(0.0));
#ifdef DEGENERATE_THRESHOLD
# ifndef DOUBLE_MANIFOLD
/* If the mesh is known to be manifold and we don't use double count,
* only create an quad if the we encounter a facing geom. */
if ((degen_faces.x && backface.y) ||
(degen_faces.y && backface.x))
return;
# endif
/* If one of the 2 triangles is degenerate, replace edge by a non-manifold one. */
backface.x = (degen_faces.x) ? !backface.y : backface.x;
backface.y = (degen_faces.y) ? !backface.x : backface.y;
is_manifold = (any(degen_faces)) ? false : is_manifold;
#endif
/* If both faces face the same direction it's not an outline edge. */
if (backface.x == backface.y) {
return;
}
#ifdef USE_INVOC_EXT
if (gl_InvocationID == 0) {
extrude_edge(backface.x);
}
else if (is_manifold) {
# ifdef DOUBLE_MANIFOLD
/* Increment/Decrement twice for manifold edges. */
extrude_edge(backface.x);
# endif
}
#else
extrude_edge(backface.x);
if (is_manifold) {
# ifdef DOUBLE_MANIFOLD
/* Increment/Decrement twice for manifold edges. */
extrude_edge(backface.x);
# endif
}
#endif
}
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