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// Draw "fancy" wireframe, displaying front-facing, back-facing and
// silhouette lines differently.
// Mike Erwin, April 2015
// After working with this shader a while, convinced we should make
// separate shaders for perpective & ortho. (Oct 2016)
// Due to perspective, the line segment's endpoints might disagree on
// whether the adjacent faces are front facing. We use a geometry
// shader to resolve this properly.
uniform mat4 ViewMatrix;
uniform mat4 ProjectionMatrix;
in vec3 pos;
in vec3 N1, N2; // normals of faces this edge joins (object coords)
/* Instance attrs */
in vec3 color;
in mat4 InstanceModelMatrix;
out vec4 MV_pos;
out float edgeClass;
out vec3 fCol;
// TODO: in float angle; // [-pi .. +pi], + peak, 0 flat, - valley
bool front(mat3 normal_matrix, vec3 N, vec3 eye)
{
return dot(normal_matrix * N, eye) > 0.0;
}
void main()
{
vec3 eye;
mat4 model_view_matrix = ViewMatrix * InstanceModelMatrix;
vec4 pos_4d = vec4(pos, 1.0);
MV_pos = model_view_matrix * pos_4d;
mat3 normal_matrix = transpose(inverse(mat3(model_view_matrix)));
/* if persp */
if (ProjectionMatrix[3][3] == 0.0) {
eye = normalize(-MV_pos.xyz);
}
else {
eye = vec3(0.0, 0.0, 1.0);
}
bool face_1_front = front(normal_matrix, N1, eye);
bool face_2_front = front(normal_matrix, N2, eye);
if (face_1_front && face_2_front) {
edgeClass = 1.0; // front-facing edge
}
else if (face_1_front || face_2_front) {
edgeClass = 0.0; // exactly one face is front-facing, silhouette edge
}
else {
edgeClass = -1.0; // back-facing edge
}
fCol = color;
#ifdef USE_WORLD_CLIP_PLANES
world_clip_planes_calc_clip_distance((InstanceModelMatrix * vec4(pos, 1.0)).xyz);
#endif
}
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