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MAPSJS-2660: Address review comments.
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Signed-off-by: Andres Mandado <andres.mandado-almajano@here.com>
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@atomicsulfate
atomicsulfate committed Aug 2, 2021
1 parent 1bf1558 commit 4d84b6c
Showing 1 changed file with 51 additions and 27 deletions.
78 changes: 51 additions & 27 deletions @here/harp-mapview/lib/ClipPlanesEvaluator.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -96,32 +96,61 @@ namespace SphericalProj {
}

/**
* Calculate distance to the nearest point where the near plane is tangent to the globe,
* projected onto the eye vector.
* Calculate distance to the nearest point where the near plane is tangent to the sphere,
* projected onto the camera forward vector.
* @param camera - The camera.
* @param halfVerticalFovAngle
* @param R - The globe radius.
* @param R - The sphere radius.
* @returns The tangent point distance if the point is visible, otherwise `undefined`.
*/
export function getProjNearPlaneTanDistance(
camera: THREE.Camera,
halfVerticalFovAngle: number,
R: number
): number | undefined {
// ,^;;;;;;;;;;;;;;;;-
// ^^^^: `;^^^:
// near plane `++^ '++^
// , :?; `*?'
// +; :\" ^\-
// {- `/: *>
// }` :^^^^` :/ '{`
// ;\N^^' :| `}`
// fwdDir ';^^^;` ,| :( }`
// up :^^^^, 90° *> } '}
// ^ :^^^^, (' \' (-
// | `;^^^;` } } }
// | ,^^^^: `} } }
// CAM<--------------------------------{$?&-------------------------O {
// \ ';;;;;;;:` ^^} :^^^^, }
// \ `;;;;;;;;, (% -^^^^;` `}
// \ `:;;;;;;;' @, 90° '^^^^;` (-
// \ camToTanVec ';;;;;;;TAN`:^^^^" -R*fwdDir ,{
// \ `:}@- `}
// \ *$ `}`
// Bottom frustum plane }$` "(
// }{^ `\;
// `}"|: >|`
// '( ,*+` '**`
// ;| ^++- :+>:
// ; ;^^^;` -;^^^,
// `;;;;;;;;;;;;;;;;"

const fwdDir = camera.getWorldDirection(tmpVectors[0]);
const nearPlaneTanPoint = tmpVectors[1].copy(fwdDir).multiplyScalar(-R);
const camToTan = nearPlaneTanPoint.sub(camera.position);
const tanDistAlongEyeDir = camToTan.dot(fwdDir);
const cosTanDirToEyeDir = tanDistAlongEyeDir / camToTan.length();
const camToTanVec = tmpVectors[1].copy(fwdDir).multiplyScalar(-R).sub(camera.position);
const near = camToTanVec.dot(fwdDir);
const cosTanDirToFwdDir = near / camToTanVec.length();

return cosTanDirToEyeDir > Math.cos(halfVerticalFovAngle) ? tanDistAlongEyeDir : undefined;
// Tangent point visible if angle from fwdDir to tangent is less than to frustum bottom.
return cosTanDirToFwdDir > Math.cos(halfVerticalFovAngle) ? near : undefined;
}

/**
* Calculate the distance to the intersection of a given ray with the globe.
* Calculate the distance to the intersection of a given ray with the sphere,
* projected onto the camera forward vector.
* @param camera - The camera.
* @param ndcDir - Ray direction in NDC coordinates.
* @param R - The globe radius.
* @param R - The sphere radius.
* @returns Intersection distance or `undefined` if there's no intersection.
*/
export function getProjSphereIntersectionDistance(
Expand Down Expand Up @@ -700,15 +729,14 @@ export class TiltViewClipPlanesEvaluator extends TopViewClipPlanesEvaluator {
z2 = cameraAltitude + sinBeta * cam.top;
z1 = cameraAltitude - sinBeta * cam.bottom;
}
// Distance along the top plane to the ground, |c2|. This will determine the far distance,
// so take the furthest distance possible, i.e. the distance to the min elevation.
// Compute |c2|. This will determine the far distance (top intersection is further away than
// bottom intersection on tilted views), so take the furthest distance possible, i.e.the
// distance to the min elevation.
// cos(topAngle) = (z2 - minElev) / |c2|
// |c2| = (z2 - minElev) / cos(topAngle)
const topDist = (z2 - this.minElevation) / Math.cos(topAngleRad);
// Distance along the bottom plane to the ground, |c1|. This will determine the near
// distance, so take the nearest distance possible, i.e. the distance to the max elevation.
// cos(bottomAngle) = (z - minElev) / |c1|
// |c1| = (z - minElev) / cos(bottomAngle)
// Compute |c1|. This will determine the near distance, so take the nearest distance
// possible, i.e.the distance to the max elevation.
const bottomDist = (z1 - this.maxElevation) / Math.cos(bottomAngleRad);

return { top: Math.max(topDist, 0), bottom: Math.max(bottomDist, 0) };
Expand All @@ -723,10 +751,7 @@ export class TiltViewClipPlanesEvaluator extends TopViewClipPlanesEvaluator {
assert(projection.type !== ProjectionType.Spherical);
const viewRanges = { ...this.minimumViewRange };

// Find intersections of top/bottom frustum side's medians with the ground plane, taking
// into account min/max elevations.Top side intersection distance determines the far
// distance (it's further away than bottom intersection on tilted views), and bottom side
// intersection distance determines the near distance.
// Find the distances to the top/bottom frustum plane intersections with the ground plane.
const planesDist = this.getFrustumGroundIntersectionDist(camera, projection);

if (camera instanceof THREE.PerspectiveCamera) {
Expand Down Expand Up @@ -794,14 +819,13 @@ export class TiltViewClipPlanesEvaluator extends TopViewClipPlanesEvaluator {
const maxR = EarthConstants.EQUATORIAL_RADIUS + this.maxElevation;
const ndcBottomDir = TiltViewClipPlanesEvaluator.NDC_BOTTOM_DIR;

// Take as near distance the distance to the point where the near plane is tangent to the
// globe. If the tangent point is not visible, take instead the distance to the intersection
// of the bottom frustum side's median and the globe.
return (
// Use as near the distance of the near plane's tangent point to the sphere. If not visible,
// use the distance to then bottom frustum side intersection.
const near =
SphericalProj.getProjNearPlaneTanDistance(camera, halfVerticalFovAngle, maxR) ??
SphericalProj.getProjSphereIntersectionDistance(camera, ndcBottomDir, maxR) ??
defaultNear
);
SphericalProj.getProjSphereIntersectionDistance(camera, ndcBottomDir, maxR);
assert(near !== undefined, "No reference point for near distance found");
return near ?? defaultNear;
}

private computeFarDistSphericalProj(
Expand Down

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