puts "========"
puts "0029074: Visualization, TKOpenGl - support Geometry Shader definition"
puts "========"

pload MODELING VISUALIZATION

set aShaderVert "
out vec4 VertColor;
void main() {
  VertColor = occColor;
  gl_Position = occVertex;
}"

# define a Geometry shader drawing shrinked triangles
set aShaderGeom "
layout(triangles) in;
layout(triangle_strip, max_vertices=3) out;
in vec4 VertColor\[3\];
out vec4 Color;
void main() {
  mat4 aMat = occProjectionMatrix * occWorldViewMatrix * occModelWorldMatrix;
  vec3 aCenter = vec3 (0.0, 0.0, 0.0);
  for (int aTriVertIter = 0; aTriVertIter < 3; ++aTriVertIter) {
    aCenter += gl_in\[aTriVertIter\].gl_Position.xyz;
  }
  aCenter /= 3.0;
  for (int aTriVertIter = 0; aTriVertIter < 3; ++aTriVertIter) {
    vec3 aVec = gl_in\[aTriVertIter\].gl_Position.xyz - aCenter;
    vec3 aVertRes = aCenter + normalize (aVec) * length (aVec) * 0.75;
    gl_Position = aMat * vec4 (aVertRes, 1.0);
    Color = VertColor\[aTriVertIter\] * 2.0;
    EmitVertex();
  }
  EndPrimitive();
}"

set aShaderFrag "
in vec4 Color;
void main() {
  occFragColor = Color;
}"

# draw a box
box b 1 2 3
vcaps -core
vclear
vinit View1
vaxo
vdisplay -dispMode 1 -mutable b
vfit
vrotate 0.2 0.0 0.0
vdump $::imagedir/${::casename}_normal.png

vshaderprog b -vert $aShaderVert -geom $aShaderGeom -frag $aShaderFrag
vdump $::imagedir/${::casename}_geom.png