layout (points, invocations = 1) in;

layout (triangle_strip, max_vertices = 24) out;

 

layout (binding = TRANSFORM) uniform transform {

    mat4 ModelViewMatrix;

    mat4 ProjectionMatrix;

    mat4 InfProjectionMatrix;

    mat4 MVPMatrix;

    vec4 Viewport;

} Transform;

 

layout (binding = DATAFIELD) uniform sampler3D dataFieldTex;

 

out TexCoord {

    smooth vec2 decalTexCoord;

} Out;

 

uniform float isolevel = 0.39;

uniform vec3 vertDecals[8];

 

const int[14] edgeTable = {

  0x0d, 0x13, 0x1e, 0x26, 0x2b, 0x35, 0x38, 0x38, 0x35, 0x2b, 0x26, 0x1e, 0x13, 0x0d

 

const int[14 * 4] triTable = {

   0,  3,  2, -1,

   0,  1,  4, -1,

   1,  4,  2,  3,

 

   1,  2,  5, -1,

   3,  5,  0,  1,

   2,  5,  0,  4,

   5,  4,  3, -1,

 

   3,  4,  5, -1,

   4,  5,  0,  2,

   1,  5,  0,  3,

   5,  2,  1, -1,

 

   3,  4,  2,  1,

   4,  1,  0, -1,

   2,  3,  0, -1,

 

void marchTetra(vec3[4] pos, float[4] val){

     //Determine the index into the edge table which

     //tells us which vertices are inside of the surface

     int tetraIndexFlag = 0;

 

     if (val[0] < isolevel) tetraIndexFlag |= 1;

     if (val[1] < isolevel) tetraIndexFlag |= 2;

     if (val[2] < isolevel) tetraIndexFlag |= 4;

     if (val[3] < isolevel) tetraIndexFlag |= 8;

 

     if (tetraIndexFlag == 0 || tetraIndexFlag == 15) return;

 

     tetraIndexFlag--;

 

     vec3 vertlist[6];

 

     if ((edgeTable[tetraIndexFlag] & 1)!=0 )

          vertlist[0] = mix(pos[0], pos[1], (isolevel-val[0])/(val[1]-val[0]));

     if ((edgeTable[tetraIndexFlag] & 2)!=0 )

      vertlist[1] = mix(pos[1], pos[2], (isolevel-val[1])/(val[2]-val[1]));

     if ((edgeTable[tetraIndexFlag] & 4)!=0)

      vertlist[2] = mix(pos[2], pos[0], (isolevel-val[2])/(val[0]-val[2]));

     if ((edgeTable[tetraIndexFlag] & 8)!=0)

      vertlist[3] = mix(pos[0], pos[3], (isolevel-val[0])/(val[3]-val[0]));

     if ((edgeTable[tetraIndexFlag] & 16)!=0)

      vertlist[4] = mix(pos[1], pos[3], (isolevel-val[1])/(val[3]-val[1]));

     if ((edgeTable[tetraIndexFlag] & 32)!=0)

      vertlist[5] = mix(pos[2], pos[3], (isolevel-val[2])/(val[3]-val[2]));

 

     gl_Position = Transform.MVPMatrix * vec4(vertlist[triTable[tetraIndexFlag * 4 ]], 1);

     Out.decalTexCoord = vertlist[triTable[tetraIndexFlag * 4 + 0]].xy;

     EmitVertex();

 

     gl_Position = Transform.MVPMatrix * vec4(vertlist[triTable[tetraIndexFlag * 4 + 1]], 1);

     Out.decalTexCoord = vertlist[triTable[tetraIndexFlag * 4 + 1]].xy;

     EmitVertex();

 

     gl_Position = Transform.MVPMatrix * vec4(vertlist[triTable[tetraIndexFlag * 4 + 2]], 1);

     Out.decalTexCoord = vertlist[triTable[tetraIndexFlag * 4 + 2]].xy;

     EmitVertex();

 

     if(triTable[tetraIndexFlag * 4 + 3] != -1){

       gl_Position = Transform.MVPMatrix * vec4(vertlist[triTable[tetraIndexFlag * 4 + 3]], 1);

       Out.decalTexCoord = vertlist[triTable[tetraIndexFlag * 4 + 3]].xy;

       EmitVertex();

     }

 

     EndPrimitive();

 

const float texshift = 1.0;

 

void main(void) {

     vec3 pos5 = gl_in[0].gl_Position.xyz + vertDecals[5];

     vec3 pos[4];

 

     pos[0] = gl_in[0].gl_Position.xyz + vertDecals[0];

     pos[1] = pos5;

     pos[2] = gl_in[0].gl_Position.xyz + vertDecals[1];

     pos[3] = gl_in[0].gl_Position.xyz + vertDecals[6];

 

     float val5 = texture(dataFieldTex, (pos5+texshift)/2).r;

     float val[4];

 

     val[0] = texture(dataFieldTex, (pos[0]+texshift)/2).r;

     val[1] = val5;

     val[2] = texture(dataFieldTex, (pos[2]+texshift)/2).r;

     val[3] = texture(dataFieldTex, (pos[3]+texshift)/2).r;

 

     marchTetra(pos, val);

 

     pos[1] = pos[2];

     pos[2] = gl_in[0].gl_Position.xyz + vertDecals[2];

     val[1] = val[2];

     val[2] = texture(dataFieldTex, (pos[2]+texshift)/2).r;

 

     marchTetra(pos, val);

 

     pos[1] = pos[2];

     pos[2] = gl_in[0].gl_Position.xyz + vertDecals[3];

     val[1] = val[2];

     val[2] = texture(dataFieldTex, (pos[2]+texshift)/2).r;

 

     marchTetra(pos, val);

 

     pos[1] = pos[2];

     pos[2] = gl_in[0].gl_Position.xyz + vertDecals[7];

     val[1] = val[2];

     val[2] = texture(dataFieldTex, (pos[2]+texshift)/2).r;

 

     marchTetra(pos, val);

 

     pos[1] = pos[2];

     pos[2] = gl_in[0].gl_Position.xyz + vertDecals[4];

     val[1] = val[2];

     val[2] = texture(dataFieldTex, (pos[2]+texshift)/2).r;

 

     marchTetra(pos, val);

 

     pos[1] = pos[2];

     pos[2] = pos5;

     val[1] = val[2];

     val[2] = val5;

 

     marchTetra(pos, val);