spg-project/resources/geometry.gs

#version 430

layout (points) in;
layout (triangle_strip, max_vertices = 12) out;

uniform mat4 proj;
uniform mat4 view;

uniform vec3 lightPos;
uniform vec3 viewPos;

in vec3 varTexture[];
in int varIndex[];

out vec3 varPositionG;
out vec2 varTextureG;
out vec3 tangentLightPosG;
out vec3 tangentViewPosG;
out vec3 tangentFragPosG;

vec3 vectors[13] = {
    vec3(0.0, 0.0, 0.0), vec3(0.5, 1.0, 1.0), vec3(0.0, 0.5, 1.0), 
    vec3(0.0, 1.0, 0.5), vec3(1.0, 0.5, 1.0), vec3(1.0, 1.0, 0.5),
    vec3(0.5, 1.0, 0.0), vec3(1.0, 0.5, 0.0), vec3(0.0, 0.5, 0.0), 
    vec3(0.0, 0.0, 0.5), vec3(0.5, 0.0, 1.0), vec3(1.0, 0.0, 0.5),
    vec3(0.5, 0.0, 0.0)};

int table[3072] = {
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,      1,  2,  3,  0,  0,  0,  0,  0,  0,  0,  0,  0, 
     4,  1,  5,  0,  0,  0,  0,  0,  0,  0,  0,  0,      3,  5,  2,  2,  5,  4,  0,  0,  0,  0,  0,  0, 
     5,  6,  7,  0,  0,  0,  0,  0,  0,  0,  0,  0,      5,  6,  7,  3,  1,  2,  0,  0,  0,  0,  0,  0, 
     7,  4,  6,  6,  4,  1,  0,  0,  0,  0,  0,  0,      3,  6,  2,  6,  7,  2,  2,  7,  4,  0,  0,  0, 
     3,  8,  6,  0,  0,  0,  0,  0,  0,  0,  0,  0,      6,  1,  8,  8,  1,  2,  0,  0,  0,  0,  0,  0, 
     6,  3,  8,  1,  5,  4,  0,  0,  0,  0,  0,  0,      6,  5,  8,  5,  4,  8,  8,  4,  2,  0,  0,  0, 
     5,  3,  7,  7,  3,  8,  0,  0,  0,  0,  0,  0,      5,  1,  7,  1,  2,  7,  7,  2,  8,  0,  0,  0, 
     1,  3,  4,  3,  8,  4,  4,  8,  7,  0,  0,  0,      8,  7,  2,  7,  4,  2,  0,  0,  0,  0,  0,  0, 
     9,  2, 10,  0,  0,  0,  0,  0,  0,  0,  0,  0,      9,  3, 10, 10,  3,  1,  0,  0,  0,  0,  0,  0, 
     4,  1,  5,  2, 10,  9,  0,  0,  0,  0,  0,  0,      4, 10,  5, 10,  9,  5,  5,  9,  3,  0,  0,  0, 
     9,  2, 10,  7,  5,  6,  0,  0,  0,  0,  0,  0,      9,  3, 10, 10,  3,  1,  6,  7,  5,  0,  0,  0, 
     7,  4,  6,  6,  4,  1, 10,  9,  2,  0,  0,  0,      4, 10,  7, 10,  3,  7,  3, 10,  9,  3,  6,  7, 
     9,  2, 10,  3,  8,  6,  0,  0,  0,  0,  0,  0,      9,  8, 10,  8,  6, 10, 10,  6,  1,  0,  0,  0, 
     8,  6,  3,  2, 10,  9,  4,  1,  5,  0,  0,  0,      5,  4,  6,  4, 10,  6, 10,  8,  6,  8, 10,  9, 
     5,  3,  7,  7,  3,  8,  2, 10,  9,  0,  0,  0,      9,  7,  1, 10,  9,  1,  7,  5,  1,  7,  9,  8, 
    10,  9,  8,  4, 10,  8,  4, 10,  7,  3,  2,  1,     10,  9,  8,  4, 10,  8,  4,  8,  7,  0,  0,  0, 
    10,  4, 11,  0,  0,  0,  0,  0,  0,  0,  0,  0,     10,  4, 11,  1,  2,  3,  0,  0,  0,  0,  0,  0, 
     5, 11,  1,  1, 11, 10,  0,  0,  0,  0,  0,  0,     10,  2, 11,  2,  3, 11, 11,  3,  5,  0,  0,  0, 
     7,  5,  6,  4, 11, 10,  0,  0,  0,  0,  0,  0,      2,  3,  1,  4, 11, 10,  7,  5,  6,  0,  0,  0, 
     7, 11,  6, 11, 10,  6,  6, 10,  1,  0,  0,  0,      6,  7,  3,  7, 11,  3, 11,  2,  3,  2, 11, 10, 
    10,  4, 11,  8,  6,  3,  0,  0,  0,  0,  0,  0,      6,  1,  8,  8,  1,  2,  4, 11, 10,  0,  0,  0, 
    10,  1, 11, 11,  1,  5,  3,  8,  6,  0,  0,  0,     10,  8,  5, 11, 10,  5,  8,  6,  5,  8, 10,  2, 
     8,  7,  3,  3,  7,  5, 11, 10,  4,  0,  0,  0,     11, 10,  2,  7, 11,  2,  7, 11,  8,  1,  4,  5, 
     7, 11,  8, 11,  1,  8,  1, 11, 10,  1,  3,  8,     11, 10,  2,  7, 11,  2,  7,  2,  8,  0,  0,  0, 
    11,  9,  4,  4,  9,  2,  0,  0,  0,  0,  0,  0,      1,  4,  3,  4, 11,  3,  3, 11,  9,  0,  0,  0, 
     2,  1,  9,  1,  5,  9,  9,  5, 11,  0,  0,  0,      3,  5,  9,  5, 11,  9,  0,  0,  0,  0,  0,  0, 
     2,  4,  9,  9,  4, 11,  5,  6,  7,  0,  0,  0,      6,  7, 11,  3,  6, 11,  3,  6,  9,  4,  5,  1, 
     1,  7,  9,  7, 11,  9,  2,  1,  9,  7,  1,  6,      6,  7, 11,  3,  6, 11,  3, 11,  9,  0,  0,  0, 
    11,  9,  4,  4,  9,  2,  8,  6,  3,  0,  0,  0,      1,  4,  6,  9,  4,  6,  9,  4, 11,  9,  8,  6, 
     8,  6,  5,  9,  8,  5,  9,  8, 11,  1,  3,  2,      8,  6,  5,  9,  8,  5,  9,  5, 11,  0,  0,  0, 
     7, 11,  9,  7,  9,  9,  4,  5,  2,  5,  2,  2,     11,  9,  8, 11,  8,  7,  1,  4,  5,  0,  0,  0, 
     8,  7, 11,  8, 11,  9,  1,  3,  2,  0,  0,  0,     11,  9,  8, 11,  8,  7,  0,  0,  0,  0,  0,  0, 
    11,  7, 12,  0,  0,  0,  0,  0,  0,  0,  0,  0,     11,  7, 12,  2,  3,  1,  0,  0,  0,  0,  0,  0, 
    11,  7, 12,  5,  4,  1,  0,  0,  0,  0,  0,  0,      3,  5,  2,  2,  5,  4,  7, 12, 11,  0,  0,  0, 
    11,  5, 12, 12,  5,  6,  0,  0,  0,  0,  0,  0,     11,  5, 12, 12,  5,  6,  1,  2,  3,  0,  0,  0, 
    11,  4, 12,  4,  1, 12, 12,  1,  6,  0,  0,  0,     11,  2,  6, 12, 11,  6,  2,  3,  6,  2, 11,  4, 
     7, 12, 11,  8,  6,  3,  0,  0,  0,  0,  0,  0,      2,  8,  1,  1,  8,  6, 12, 11,  7,  0,  0,  0, 
     4,  1,  5,  7, 12, 11,  8,  6,  3,  0,  0,  0,     12, 11,  4,  8, 12,  4,  8, 12,  2,  5,  7,  6, 
     8, 12,  3, 12, 11,  3,  3, 11,  5,  0,  0,  0,      8, 12,  2, 12,  5,  2,  5, 12, 11,  5,  1,  2, 
     3,  8,  1,  8, 12,  1, 12,  4,  1,  4, 12, 11,     12, 11,  4,  8, 12,  4,  8,  4,  2,  0,  0,  0, 
    12, 11,  7, 10,  9,  2,  0,  0,  0,  0,  0,  0,      1, 10,  3,  3, 10,  9, 11,  7, 12,  0,  0,  0, 
     7, 12, 11,  4,  1,  5,  2, 10,  9,  0,  0,  0,      7, 12,  9,  5,  7,  9,  5,  7,  3, 10, 11,  4, 
     6, 12,  5,  5, 12, 11,  9,  2, 10,  0,  0,  0,     12,  9,  3, 12,  3,  3, 10, 11,  1, 11,  1,  1, 
    11,  4, 12,  4,  1, 12,  4,  1,  6, 10,  9,  2,      9,  3,  6,  9,  6, 12,  4, 10, 11,  0,  0,  0, 
     6,  3,  8, 12, 11,  7, 10,  9,  2,  0,  0,  0,     11,  7,  6, 10, 11,  6, 10, 11,  1,  8, 12,  9, 
     8, 12,  9,  7,  6,  5,  2,  1,  3,  7,  6,  5,      9,  8, 12,  5,  7,  6, 11,  4, 10,  0,  0,  0, 
     8, 12,  3, 12, 11,  3, 12, 11,  5,  9,  2, 10,     11,  5,  1, 11,  1, 10,  8, 12,  9,  0,  0,  0, 
     8, 12,  9,  4, 10, 11,  2,  1,  3,  0,  0,  0,     10, 11,  4, 12,  9,  8,  0,  0,  0,  0,  0,  0, 
    12, 10,  7,  7, 10,  4,  0,  0,  0,  0,  0,  0,     12, 10,  7,  7, 10,  4,  2,  3,  1,  0,  0,  0, 
     5,  7,  1,  7, 12,  1,  1, 12, 10,  0,  0,  0,      7, 12, 10,  3,  7, 10,  7,  3,  5,  2,  3, 10, 
     4,  5, 10,  5,  6, 10, 10,  6, 12,  0,  0,  0,      4,  5, 10,  5,  6, 10,  5,  6, 12,  1,  2,  3, 
     6, 12, 10,  1,  6, 10,  0,  0,  0,  0,  0,  0,      2,  3,  6, 10,  2,  6, 10,  6, 12,  0,  0,  0, 
     4,  7, 10, 10,  7, 12,  6,  3,  8,  0,  0,  0,      8,  6,  2,  6,  2,  2,  7, 12, 10,  7, 10, 10, 
     5,  7,  1,  7, 12,  1,  7, 12, 10,  6,  3,  8,     12, 10,  2, 12,  2,  8,  5,  7,  6,  0,  0,  0, 
     4, 12,  3,  4,  5,  3,  8, 12,  3,  4, 12, 10,      2,  8, 12,  2, 12, 10,  5,  1,  4,  0,  0,  0, 
     3,  8, 12,  1,  3, 12,  1, 12, 10,  0,  0,  0,     12, 10,  2, 12,  2,  8,  0,  0,  0,  0,  0,  0, 
    12,  9,  7,  9,  2,  7,  7,  2,  4,  0,  0,  0,      4, 12,  3, 12,  9,  3,  1,  4,  3, 12,  4,  7, 
     2,  1,  5,  9,  2,  5,  7,  9,  5,  9,  7, 12,      7, 12,  9,  5,  7,  9,  5,  9,  3,  0,  0,  0, 
     9,  2,  4,  6,  9,  4,  9,  6, 12,  5,  6,  4,      6, 12,  9,  6,  9,  3,  4,  5,  1,  0,  0,  0, 
     9,  2,  1, 12,  9,  1, 12,  1,  6,  0,  0,  0,      9,  3,  6,  9,  6, 12,  0,  0,  0,  0,  0,  0, 
    12,  9,  7,  9,  2,  7,  9,  2,  4,  8,  6,  3,      6,  1,  4,  6,  4,  7,  9,  8, 12,  0,  0,  0, 
     5,  7,  6,  9,  8, 12,  3,  2,  1,  0,  0,  0,      8, 12,  9,  7,  6,  5,  0,  0,  0,  0,  0,  0, 
     2,  4,  5,  2,  5,  3, 12,  9,  8,  0,  0,  0,      8, 12,  9,  1,  4,  5,  0,  0,  0,  0,  0,  0, 
     9,  8, 12,  3,  2,  1,  0,  0,  0,  0,  0,  0,      8, 12,  9,  0,  0,  0,  0,  0,  0,  0,  0,  0, 
    12,  8,  9,  0,  0,  0,  0,  0,  0,  0,  0,  0,      8,  9, 12,  2,  3,  1,  0,  0,  0,  0,  0,  0, 
    12,  8,  9,  4,  1,  5,  0,  0,  0,  0,  0,  0,      4,  2,  5,  5,  2,  3,  9, 12,  8,  0,  0,  0, 
    12,  8,  9,  6,  7,  5,  0,  0,  0,  0,  0,  0,      7,  5,  6,  8,  9, 12,  2,  3,  1,  0,  0,  0, 
     1,  6,  4,  4,  6,  7,  8,  9, 12,  0,  0,  0,      9, 12,  7,  2,  9,  7,  2,  9,  4,  6,  8,  3, 
     3,  9,  6,  6,  9, 12,  0,  0,  0,  0,  0,  0,      2,  9,  1,  9, 12,  1,  1, 12,  6,  0,  0,  0, 
    12,  6,  9,  9,  6,  3,  5,  4,  1,  0,  0,  0,      2,  9,  4,  9,  6,  4,  6,  9, 12,  6,  5,  4, 
    12,  7,  9,  7,  5,  9,  9,  5,  3,  0,  0,  0,      1,  2,  5,  2,  9,  5,  9,  7,  5,  7,  9, 12, 
    12,  4,  3,  9, 12,  3,  4,  1,  3,  4, 12,  7,      9, 12,  7,  2,  9,  7,  2,  7,  4,  0,  0,  0, 
    10, 12,  2,  2, 12,  8,  0,  0,  0,  0,  0,  0,      8,  3, 12,  3,  1, 12, 12,  1, 10,  0,  0,  0, 
     8,  2, 12, 12,  2, 10,  1,  5,  4,  0,  0,  0,     12,  4,  3,  5,  4,  3, 12,  8,  3, 12,  4, 10, 
    10, 12,  2,  2, 12,  8,  7,  5,  6,  0,  0,  0,      7,  5,  1, 12,  7,  1, 12,  7, 10,  3,  6,  8, 
     6,  8,  2,  6,  2,  2, 12,  7, 10,  7, 10, 10,      7,  4, 10,  7, 10, 12,  3,  6,  8,  0,  0,  0, 
     3,  2,  6,  2, 10,  6,  6, 10, 12,  0,  0,  0,     12,  6, 10,  6,  1, 10,  0,  0,  0,  0,  0,  0, 
     5,  4, 10,  6,  5, 10,  6,  5, 12,  2,  1,  3,      5,  4, 10,  6,  5, 10,  6, 10, 12,  0,  0,  0, 
    12,  7, 10,  7,  3, 10,  3,  7,  5,  3,  2, 10,      7,  5,  1, 12,  7,  1, 12,  1, 10,  0,  0,  0, 
    10, 12,  7, 10,  7,  4,  3,  2,  1,  0,  0,  0,     10, 12,  7, 10,  7,  4,  0,  0,  0,  0,  0,  0, 
    11, 10,  4,  9, 12,  8,  0,  0,  0,  0,  0,  0,     12,  8,  9, 10,  4, 11,  1,  2,  3,  0,  0,  0, 
     5, 11,  1,  1, 11, 10, 12,  8,  9,  0,  0,  0,     12,  8,  3, 11, 12,  3, 11, 12,  5,  2,  9, 10, 
     8,  9, 12,  7,  5,  6,  4, 11, 10,  0,  0,  0,     12,  8,  9,  6,  7,  5,  1,  2,  3,  6,  7,  5, 
     7, 11,  6, 11, 10,  6, 11, 10,  1, 12,  8,  9,      3,  6,  8, 11, 12,  7,  9, 10,  2,  0,  0,  0, 
     3,  9,  6,  6,  9, 12, 10,  4, 11,  0,  0,  0,      4, 11, 12,  1,  4, 12,  1,  4,  6,  9, 10,  2, 
     9, 12,  3, 12,  3,  3, 11, 10,  1, 11,  1,  1,     12,  6,  5, 12,  5, 11,  2,  9, 10,  0,  0,  0, 
    12,  7,  9,  7,  5,  9,  7,  5,  3, 11, 10,  4,     12,  7, 11,  1,  4,  5, 10,  2,  9,  0,  0,  0, 
    10,  1,  3, 10,  3,  9,  7, 11, 12,  0,  0,  0,     11, 12,  7,  9, 10,  2,  0,  0,  0,  0,  0,  0, 
    11, 12,  4, 12,  8,  4,  4,  8,  2,  0,  0,  0,      8,  3,  1, 12,  8,  1,  4, 12,  1, 12,  4, 11, 
    12,  8,  2,  5, 12,  2, 12,  5, 11,  1,  5,  2,     12,  8,  3, 11, 12,  3, 11,  3,  5,  0,  0,  0, 
    11, 12,  4, 12,  8,  4, 12,  8,  2,  7,  5,  6,      1,  4,  5, 12,  7, 11,  6,  8,  3,  0,  0,  0, 
     8,  2,  1,  8,  1,  6, 11, 12,  7,  0,  0,  0,     12,  7, 11,  6,  8,  3,  0,  0,  0,  0,  0,  0, 
     2, 11,  6, 11, 12,  6,  3,  2,  6, 11,  2,  4,      4, 11, 12,  1,  4, 12,  1, 12,  6,  0,  0,  0, 
     5, 11, 12,  5, 12,  6,  2,  1,  3,  0,  0,  0,      5, 11, 12,  5, 12,  6,  0,  0,  0,  0,  0,  0, 
     5,  3,  2,  5,  2,  4, 12,  7, 11,  0,  0,  0,      7, 11, 12,  4,  5,  1,  0,  0,  0,  0,  0,  0, 
     7, 11, 12,  3,  2,  1,  0,  0,  0,  0,  0,  0,      7, 11, 12,  0,  0,  0,  0,  0,  0,  0,  0,  0, 
     9, 11,  8,  8, 11,  7,  0,  0,  0,  0,  0,  0,      7,  8, 11, 11,  8,  9,  3,  1,  2,  0,  0,  0, 
     9, 11,  8,  8, 11,  7,  4,  1,  5,  0,  0,  0,     11,  7,  9,  7,  9,  9,  5,  4,  2,  5,  2,  2, 
     6,  8,  5,  8,  9,  5,  5,  9, 11,  0,  0,  0,      6,  8,  5,  8,  9,  5,  8,  9, 11,  3,  1,  2, 
     4,  1,  6,  4,  9,  6,  4,  9, 11,  8,  9,  6,      9, 11,  4,  9,  4,  2,  6,  8,  3,  0,  0,  0, 
     7,  6, 11,  6,  3, 11, 11,  3,  9,  0,  0,  0,      7,  1,  9, 11,  7,  9,  1,  2,  9,  1,  7,  6, 
     7,  6, 11,  6,  3, 11,  6,  3,  9,  5,  4,  1,      4,  2,  9,  4,  9, 11,  6,  5,  7,  0,  0,  0, 
     5,  3,  9, 11,  5,  9,  0,  0,  0,  0,  0,  0,      1,  2,  9,  5,  1,  9,  5,  9, 11,  0,  0,  0, 
     4,  1,  3, 11,  4,  3, 11,  3,  9,  0,  0,  0,      9, 11,  4,  9,  4,  2,  0,  0,  0,  0,  0,  0, 
    10, 11,  2, 11,  7,  2,  2,  7,  8,  0,  0,  0,     11,  7,  8,  1, 11,  8, 11,  1, 10,  3,  1,  8, 
    10, 11,  2, 11,  7,  2, 11,  7,  8,  4,  1,  5,      7,  8,  3,  7,  3,  5, 10, 11,  4,  0,  0,  0, 
     8, 10,  5, 10, 11,  5,  6,  8,  5, 10,  8,  2,      1, 10, 11,  1, 11,  5,  8,  3,  6,  0,  0,  0, 
     1,  6,  8,  1,  8,  2, 11,  4, 10,  0,  0,  0,      4, 10, 11,  6,  8,  3,  0,  0,  0,  0,  0,  0, 
     7,  6,  3, 11,  7,  3,  2, 11,  3, 11,  2, 10,     11,  7,  6, 10, 11,  6, 10,  6,  1,  0,  0,  0, 
     3,  2,  1, 11,  4, 10,  5,  7,  6,  0,  0,  0,      5,  7,  6, 11,  4, 10,  0,  0,  0,  0,  0,  0, 
     2, 10, 11,  3,  2, 11,  3, 11,  5,  0,  0,  0,     11,  5,  1, 11,  1, 10,  0,  0,  0,  0,  0,  0, 
     4, 10, 11,  2,  1,  3,  0,  0,  0,  0,  0,  0,      4, 10, 11,  0,  0,  0,  0,  0,  0,  0,  0,  0, 
     9, 10,  8, 10,  4,  8,  8,  4,  7,  0,  0,  0,      9, 10,  8, 10,  4,  8, 10,  4,  7,  2,  3,  1, 
     7,  9,  1,  9, 10,  1,  5,  7,  1,  9,  7,  8,      3,  5,  7,  3,  7,  8, 10,  2,  9,  0,  0,  0, 
     4,  5,  6, 10,  4,  6,  8, 10,  6, 10,  8,  9,      6,  8,  3, 10,  2,  9,  1,  4,  5,  0,  0,  0, 
     8,  9, 10,  6,  8, 10,  6, 10,  1,  0,  0,  0,      2,  9, 10,  8,  3,  6,  0,  0,  0,  0,  0,  0, 
    10,  4,  7,  3, 10,  7, 10,  3,  9,  6,  3,  7,      4,  7,  6,  4,  6,  1,  9, 10,  2,  0,  0,  0, 
     3,  9, 10,  3, 10,  1,  7,  6,  5,  0,  0,  0,      2,  9, 10,  5,  7,  6,  0,  0,  0,  0,  0,  0, 
    10,  4,  5,  9, 10,  5,  9,  5,  3,  0,  0,  0,      1,  4,  5, 10,  2,  9,  0,  0,  0,  0,  0,  0, 
     3,  9, 10,  3, 10,  1,  0,  0,  0,  0,  0,  0,      2,  9, 10,  0,  0,  0,  0,  0,  0,  0,  0,  0, 
     7,  8,  2,  4,  7,  2,  0,  0,  0,  0,  0,  0,      3,  1,  4,  8,  3,  4,  8,  4,  7,  0,  0,  0, 
     1,  5,  7,  2,  1,  7,  2,  7,  8,  0,  0,  0,      3,  5,  7,  3,  7,  8,  0,  0,  0,  0,  0,  0, 
     5,  6,  8,  4,  5,  8,  4,  8,  2,  0,  0,  0,      3,  6,  8,  5,  1,  4,  0,  0,  0,  0,  0,  0, 
     1,  6,  8,  1,  8,  2,  0,  0,  0,  0,  0,  0,      8,  3,  6,  0,  0,  0,  0,  0,  0,  0,  0,  0, 
     6,  3,  2,  7,  6,  2,  7,  2,  4,  0,  0,  0,      4,  7,  6,  4,  6,  1,  0,  0,  0,  0,  0,  0, 
     6,  5,  7,  1,  3,  2,  0,  0,  0,  0,  0,  0,      6,  5,  7,  0,  0,  0,  0,  0,  0,  0,  0,  0, 
     5,  3,  2,  5,  2,  4,  0,  0,  0,  0,  0,  0,      1,  4,  5,  0,  0,  0,  0,  0,  0,  0,  0,  0, 
     2,  1,  3,  0,  0,  0,  0,  0,  0,  0,  0,  0,      0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
};

const float step = 1.0 / 63.0;

void main(void) {	
    vec4 base = gl_in[0].gl_Position;
    int index = varIndex[0] * 12;
    for(int i = 0; i < 12; i += 3) {
        vec3 offsetA = vectors[table[index + i + 0]];
        vec3 offsetB = vectors[table[index + i + 1]];
        vec3 offsetC = vectors[table[index + i + 2]];

        // position
        vec3 a = base.xyz + offsetA;
        vec3 b = base.xyz + offsetB;
        vec3 c = base.xyz + offsetC;
        // texture coords
        vec2 ta = (varTexture[0] + offsetA * step).xy;
        vec2 tb = (varTexture[0] + offsetB * step).xy;
        vec2 tc = (varTexture[0] + offsetC * step).xy;
        // normal, same for all vertices
        vec3 ab = b - a;
        vec3 ac = c - a;
        vec3 normal = normalize(cross(ab, ac));
        // tangent, same for all vertices
        vec2 abt = tb - ta;
        vec2 act = tc - ta;
        float f = 1.0f / (abt.x * act.y - act.x * abt.y);
        vec3 tangent = normalize(f * (act.y * ab - abt.y * ac));

        vec3 biTangent = cross(normal, tangent);

        mat3 TBN = transpose(mat3(tangent, biTangent, normal));
        vec3 tangentLightPos = TBN * lightPos;
        vec3 tangentViewPos  = TBN * viewPos;

        gl_Position = proj * view * vec4(a, 1.0);
        varPositionG = a;
        varTextureG = ta;
        tangentLightPosG = tangentLightPos;
        tangentViewPosG = tangentViewPos;
        tangentFragPosG = TBN * a;
        EmitVertex();

        gl_Position = proj * view * vec4(b, 1.0);
        varPositionG = b;
        varTextureG = tb;
        tangentLightPosG = tangentLightPos;
        tangentViewPosG = tangentViewPos;
        tangentFragPosG = TBN * b;
        EmitVertex();

        gl_Position = proj * view * vec4(c, 1.0);
        varPositionG = c;
        varTextureG = tc;
        tangentLightPosG = tangentLightPos;
        tangentViewPosG = tangentViewPos;
        tangentFragPosG = TBN * c;
        EmitVertex();

        EndPrimitive();
    }
}