puts "========"
puts "0029074: Visualization, TKOpenGl - support of Tessellation Shaders"
puts "========"

pload MODELING VISUALIZATION

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

set aShaderTessCtrl "
layout(vertices = 3) out;
void main() {
  if (gl_InvocationID == 0) {
    gl_TessLevelInner\[0\] = 7.0;
    gl_TessLevelOuter\[0\] = 2.0;
    gl_TessLevelOuter\[1\] = 3.0;
    gl_TessLevelOuter\[2\] = 7.0;
  }
  gl_out\[gl_InvocationID\].gl_Position = gl_in\[gl_InvocationID\].gl_Position;
}"

set aShaderTessEval "
layout(triangles, equal_spacing, ccw) in;
void main() {
  vec3 aPnt0 = gl_TessCoord.x * gl_in\[0\].gl_Position.xyz;
  vec3 aPnt1 = gl_TessCoord.y * gl_in\[1\].gl_Position.xyz;
  vec3 aPnt2 = gl_TessCoord.z * gl_in\[2\].gl_Position.xyz;
  gl_Position = vec4 (aPnt0 + aPnt1 + aPnt2, 1.0);
}"

set aShaderGeom "
layout(triangles) in;
layout(triangle_strip, max_vertices=3) out;
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);
    EmitVertex();
  }
  EndPrimitive();
}"

set aShaderFrag "
void main() {
  occFragColor = vec4(1.0, 0.0, 0.0, 1.0);
}"

# draw a box
box b 1 2 3
explode b F

vcaps -core
vclear
vinit View1
vaxo
vdisplay -dispMode 1 -mutable b_1
vfit
vrotate 0.2 0.0 0.0

# take snapshot with built-in shader
vdump $::imagedir/${::casename}_normal.png

vshaderprog b_1 -vert $aShaderVert -tessCtrl $aShaderTessCtrl -tessEval $aShaderTessEval -geom $aShaderGeom -frag $aShaderFrag
vdump $::imagedir/${::casename}_tess.png