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void MAIN() {
//Catmull-Rom spline
float curveIndex = UV0.y;
float step = 1.0f / float(points);
//add small offset to avoid sampling the edge of each texture pixel
float pixelOffset = step * 0.1f;
vec3 p0 = texture(controlPoints, vec2(curveIndex + pixelOffset, 0.5f)).xyz;
vec3 p1 = texture(controlPoints, vec2(curveIndex + step + pixelOffset , 0.5f)).xyz;
vec3 p2 = texture(controlPoints, vec2(curveIndex + 2.0f*step + pixelOffset , 0.5f)).xyz;
vec3 p3 = texture(controlPoints, vec2(curveIndex + 3.0f*step + pixelOffset , 0.5f)).xyz;
// check if looping segment
float lastThresh = 1.0f - (1.0f / float(points - 2.0f)) - 0.001f;
bool lastSegment = (curveIndex * points) / (points - 2.0f) >= lastThresh;
if (loop && lastSegment) {
p2 = texture(controlPoints, vec2(step, 0.5f)).xyz;
p3 = texture(controlPoints, vec2(2.0f* step, 0.5f)).xyz;
}
float t01 = pow(distance(p0, p1), knotting);
float t12 = pow(distance(p1, p2), knotting);
float t23 = pow(distance(p2, p3), knotting);
vec3 m1 = (1.0f - tension) *
(p2 - p1 + t12 * ((p1 - p0) / t01 - (p2 - p0) / (t01 + t12)));
vec3 m2 = (1.0f - tension) *
(p2 - p1 + t12 * ((p3 - p2) / t23 - (p3 - p1) / (t12 + t23)));
vec3 A = 2.0f * (p1 - p2) + m1 + m2;
vec3 B = -3.0f * (p1 - p2) - m1 - m1 - m2;
vec3 C = m1;
vec3 D = p1;
float t = UV0.x;
vec3 point =
A * t * t * t +
B * t * t +
C * t +
D;
vec4 pos = MODELVIEWPROJECTION_MATRIX * vec4(point, 1.0f);
POSITION = pos;
}
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