void clipLineSegmentToNearPlane(
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vec3 p0,
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vec3 p1,
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out vec4 positionWC,
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out bool clipped,
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out bool culledByNearPlane,
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out vec4 clippedPositionEC)
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{
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culledByNearPlane = false;
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clipped = false;
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vec3 p1ToP0 = p1 - p0;
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float magnitude = length(p1ToP0);
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vec3 direction = normalize(p1ToP0);
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float endPoint0Distance = -(czm_currentFrustum.x + p0.z);
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float denominator = -direction.z;
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if (endPoint0Distance < 0.0 && abs(denominator) < czm_epsilon7)
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{
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culledByNearPlane = true;
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}
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else if (endPoint0Distance < 0.0)
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{
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// t = (-plane distance - dot(plane normal, ray origin)) / dot(plane normal, ray direction)
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float t = (czm_currentFrustum.x + p0.z) / denominator;
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if (t < 0.0 || t > magnitude)
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{
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culledByNearPlane = true;
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}
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else
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{
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p0 = p0 + t * direction;
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clipped = true;
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}
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}
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clippedPositionEC = vec4(p0, 1.0);
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positionWC = czm_eyeToWindowCoordinates(clippedPositionEC);
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}
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vec4 getPolylineWindowCoordinatesEC(vec4 positionEC, vec4 prevEC, vec4 nextEC, float expandDirection, float width, bool usePrevious, out float angle)
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{
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vec4 endPointWC, p0, p1;
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bool culledByNearPlane, clipped;
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#ifdef POLYLINE_DASH
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// Compute the window coordinates of the points.
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vec4 positionWindow = czm_eyeToWindowCoordinates(positionEC);
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vec4 previousWindow = czm_eyeToWindowCoordinates(prevEC);
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vec4 nextWindow = czm_eyeToWindowCoordinates(nextEC);
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// Determine the relative screen space direction of the line.
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vec2 lineDir;
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if (usePrevious) {
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lineDir = normalize(positionWindow.xy - previousWindow.xy);
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}
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else {
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lineDir = normalize(nextWindow.xy - positionWindow.xy);
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}
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angle = atan(lineDir.x, lineDir.y) - 1.570796327; // precomputed atan(1,0)
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// Quantize the angle so it doesn't change rapidly between segments.
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angle = floor(angle / czm_piOverFour + 0.5) * czm_piOverFour;
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#endif
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vec4 clippedPositionEC;
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clipLineSegmentToNearPlane(prevEC.xyz, positionEC.xyz, p0, clipped, culledByNearPlane, clippedPositionEC);
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clipLineSegmentToNearPlane(nextEC.xyz, positionEC.xyz, p1, clipped, culledByNearPlane, clippedPositionEC);
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clipLineSegmentToNearPlane(positionEC.xyz, usePrevious ? prevEC.xyz : nextEC.xyz, endPointWC, clipped, culledByNearPlane, clippedPositionEC);
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#ifdef LOG_DEPTH
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czm_vertexLogDepth(czm_projection * clippedPositionEC);
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#endif
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if (culledByNearPlane)
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{
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return vec4(0.0, 0.0, 0.0, 1.0);
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}
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vec2 prevWC = normalize(p0.xy - endPointWC.xy);
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vec2 nextWC = normalize(p1.xy - endPointWC.xy);
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float expandWidth = width * 0.5;
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vec2 direction;
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#ifdef CLIP_POLYLINE
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if (clipped)
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{
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if (prevEC.z - positionEC.z < 0.0)
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{
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direction = vec2(prevWC.y, -prevWC.x);
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}
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else
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{
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direction = vec2(-prevWC.y, prevWC.x);
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}
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}
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else
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#endif
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if (czm_equalsEpsilon(prevEC.xyz - positionEC.xyz, vec3(0.0), czm_epsilon1) || czm_equalsEpsilon(prevWC, -nextWC, czm_epsilon1))
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{
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direction = vec2(-nextWC.y, nextWC.x);
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}
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else if (czm_equalsEpsilon(nextEC.xyz - positionEC.xyz, vec3(0.0), czm_epsilon1))
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{
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direction = vec2(prevWC.y, -prevWC.x);
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}
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else
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{
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vec2 normal = vec2(-nextWC.y, nextWC.x);
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direction = normalize((nextWC + prevWC) * 0.5);
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if (dot(direction, normal) < 0.0)
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{
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direction = -direction;
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}
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// The sine of the angle between the two vectors is given by the formula
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// |a x b| = |a||b|sin(theta)
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// which is
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// float sinAngle = length(cross(vec3(direction, 0.0), vec3(nextWC, 0.0)));
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// Because the z components of both vectors are zero, the x and y coordinate will be zero.
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// Therefore, the sine of the angle is just the z component of the cross product.
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float sinAngle = abs(direction.x * nextWC.y - direction.y * nextWC.x);
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expandWidth = clamp(expandWidth / sinAngle, 0.0, width * 2.0);
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}
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vec2 offset = direction * expandDirection * expandWidth * czm_pixelRatio;
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return vec4(endPointWC.xy + offset, -endPointWC.z, 1.0);
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}
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vec4 getPolylineWindowCoordinates(vec4 position, vec4 previous, vec4 next, float expandDirection, float width, bool usePrevious, out float angle)
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{
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vec4 positionEC = czm_modelViewRelativeToEye * position;
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vec4 prevEC = czm_modelViewRelativeToEye * previous;
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vec4 nextEC = czm_modelViewRelativeToEye * next;
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return getPolylineWindowCoordinatesEC(positionEC, prevEC, nextEC, expandDirection, width, usePrevious, angle);
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}
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