geometryShader.glsl

#version 430 core

layout(triangles) in;
layout(triangle_strip, max_vertices = 3) out;

uniform vec3 viewPos;
uniform vec3 lightPos;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;

uniform sampler2D heightsTexture;
uniform sampler2D normalTexture;

out vec3 tangentLightPos;
out vec3 tangentViewPos;
out vec3 tangentFragPos;

in TE_OUT {
  vec3 FragPos;
  vec2 TexCoords;
  vec3 TangentLightPos;
  vec3 TangentViewPos;
  vec3 TangentFragPos;
  float incUV;
} gs_in[];

out GS_OUT {
  vec3 FragPos;
  vec2 TexCoords;
  vec3 TangentLightPos;
  vec3 TangentViewPos;
  vec3 TangentFragPos;
  vec3 normal;
  float hBase;
  vec3 T;
  vec3 B;
  vec3 N;
  float incUV;
} gs_out;

void main(void) {
  vec3 edge1 = gl_in[1].gl_Position.xyz - gl_in[0].gl_Position.xyz;
  vec3 edge2 = gl_in[2].gl_Position.xyz - gl_in[0].gl_Position.xyz;

  vec2 deltaUV1  = gs_in[1].TexCoords - gs_in[0].TexCoords;
  vec2 deltaUV2  = gs_in[2].TexCoords - gs_in[0].TexCoords;

  float f = 1.0f / (deltaUV1.x * deltaUV2.y - deltaUV2.x * deltaUV1.y); 

  vec3 tang;
  vec3 bitang;

  tang.x = f * (deltaUV2.y * edge1.x - deltaUV1.y * edge2.x);
  tang.y = f * (deltaUV2.y * edge1.y - deltaUV1.y * edge2.y);
  tang.z = f * (deltaUV2.y * edge1.z - deltaUV1.y * edge2.z);

  bitang.x = f * (-deltaUV2.x * edge1.x + deltaUV1.x * edge2.x);
  bitang.y = f * (-deltaUV2.x * edge1.y + deltaUV1.x * edge2.y);
  bitang.z = f * (-deltaUV2.x * edge1.z + deltaUV1.x * edge2.z);

  vec3 normal = cross(bitang, tang);

  vec3 T = normalize(mat3(model) * tang);
  vec3 B = normalize(mat3(model) * bitang);
  vec3 N = normalize(mat3(model) * normal);
  mat3 TBN = transpose(mat3(T, B, N));
  
  for( int i=0; i < gl_in.length( ); i++ ) {
    gs_out.TexCoords = gs_in[i].TexCoords;
    gs_out.hBase = gl_in[i].gl_Position.y / 10;
    gs_out.normal = normalize(normal);
    gs_out.T = tang;
    gs_out.B = bitang;
    gs_out.N = normalize(normal);
    
    gl_Position = projection * view * model * vec4(gl_in[i].gl_Position.xyz, 1.f);

    vec3 fragPos = vec3(model * vec4(gl_in[i].gl_Position.xyz, 1.0));
    gs_out.TangentFragPos  = TBN * fragPos;
    gs_out.TangentLightPos = TBN * lightPos;
    gs_out.TangentViewPos  = TBN * viewPos;
    gs_out.incUV = gs_in[i].incUV;
    gs_out.FragPos = fragPos;

    EmitVertex();
  }

  EndPrimitive( );
}