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#version 440
layout(location = 0) in vec4 vertexCoord;
layout(location = 1) in vec2 inA;
layout(location = 2) in vec2 inB;
layout(location = 3) in vec2 inC;
layout(location = 4) in vec2 normalVector;
layout(location = 0) out vec4 P;
layout(location = 1) out vec2 A;
layout(location = 2) out vec2 B;
layout(location = 3) out vec2 C;
layout(location = 4) out vec2 HG;
layout(location = 5) out float offset;
layout(std140, binding = 0) uniform buf {
#if QSHADER_VIEW_COUNT >= 2
mat4 qt_Matrix[QSHADER_VIEW_COUNT];
#else
mat4 qt_Matrix;
#endif
float matrixScale;
float opacity;
float reserved2;
float reserved3;
vec4 strokeColor;
float strokeWidth;
float debug;
float reserved5;
float reserved6;
} ubuf;
#define SQRT2 1.41421356237
float qdot(vec2 a, vec2 b)
{
return a.x * b.x + a.y * b.y;
}
void main()
{
P = vertexCoord + vec4(normalVector, 0.0, 0.0) * SQRT2/ubuf.matrixScale;
A = inA;
B = inB;
C = inC;
// Find the parameters H, G for the depressed cubic
// t^2+H*t+G=0
// that results from the equation
// Q'(s).(p-Q(s)) = 0
// The last parameter is the static offset between s and t:
// s = t - b/(3a)
// use it to get back the parameter t
// this is a constant for the curve
float a = -2. * qdot(A, A);
// this is a constant for the curve
float b = -3. * qdot(A, B);
//this is linear in p so it can be put into the shader with vertex data
float c = 2. * qdot(A, P.xy) - qdot(B, B) - 2. * qdot(A, C);
//this is linear in p so it can be put into the shader with vertex data
float d = qdot(B, P.xy) - qdot(B, C);
// convert to depressed cubic.
// both functions are linear in c and d and thus linear in p
float H = (3. * a * c - b * b) / (3. * a * a);
float G = (2. * b * b * b - 9. * a * b * c + 27. * a * a * d) / (27. * a * a * a);
HG = vec2(H, G);
offset = b/(3*a);
#if QSHADER_VIEW_COUNT >= 2
gl_Position = ubuf.qt_Matrix[gl_ViewIndex] * P;
#else
gl_Position = ubuf.qt_Matrix * P;
#endif
}
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