Add files

shader/functions.glsl

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+float closestPointOnLineParam (vec2 a, vec2 b, vec2 p) {
+  return dot(p - a,b-a) / dot(b-a,b-a);
+}
+vec2 closestPointOnSeg (vec2 a,vec2 b, vec2 p) {
+  float x = closestPointOnLineParam(a,b,p);
+  if (x < 0) {
+      return a;
+  } else{ if (x > 1) { return b; }
+      { return a + (x * (b- a));}
+  }
+}

shader/shape/basic.frag

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+#version 450 core
+in vec4 vCol;
+in vec4 vPos;
+layout (location=0) out vec4 fCol;
+layout (location=1) out vec4 fPos;
+void main()
+{
+  fCol = vCol;
+  fPos = vec4(vPos.xyz,1);
+}

shader/shape/basic.vert

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+#version 450 core
+layout (location = 0) in vec4 pos;
+layout (location = 1) in vec4 col;
+layout (std140, binding = 0) uniform TheMat { mat4 theMat; } ;
+out vec4 vCol;
+out vec4 vPos;
+void main() {
+  gl_Position = theMat * vec4(pos.xyz,1);
+  vCol = col;
+  vPos = pos;
+}