How to determine thickness vs width? (Using Raycasting) - unity3d

Question

Visual aids
Thickness vs width: here
Please view the short gif.
Thickness here is different from width as there are multiple walls as there are outer and inner cylinders. Thickness is the measurement of the distance between the outer/inner wall of any side of the cylinder where as thickness is the distance from one end to the other encompassing the hollow space between.
Quick synopsis on the gifs provided
-On every click the origin point (blue) and destination point (orange) orbs are created to denote where the user clicks and the interpreted end point used to calculate the distance (displayed on the GUI).
The origin defines where the user clicks on the surface of an objects collider and the destination defines the point, perpendicular with the world Y axis of the origin, where a second ray cast towards the first ray, hits the other side of the collider.
Current:
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
RaycastHit hit;
if (Physics.Raycast(ray, out hit))
{
//obtain the vector where the ray hit the collider.
hitPoint = hit.point; //origin point
//offset the ray, keeping it along the XZ plane of the hit
Vector3 offsetDirection = -1 * hit.normal;
//offset a long way, minimum thickness of the object
ray.origin = hit.point + offsetDirection * 100;
//point the ray back at the first hit point
ray.direction = (hit.point - ray.origin).normalized;
//raycast all, because there might be other objects in the way
RaycastHit[] hits = Physics.RaycastAll(ray);
foreach (RaycastHit h in hits)
{
if (h.collider == hit.collider)
{
hitBack = h.point; //destination point
}
}
}
Currently, width is the functionality in place. I want to calculate thickness without having to go inside of an object (as seen in the gif).
Amazing reference
http://answers.unity3d.com/questions/386698/detecting-how-many-times-a-raycast-collides-with-a.html
This guy basically had the same question as me and has a solution that could possibly work. I'm not sure how Linecasting works vs Raycasting.

Answer 1

Keep:
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
RaycastHit hit;
if (Physics.Raycast(ray, out hit))
{
//obtain the vector where the ray hit the collider.
hitPoint = hit.point; //origin point
//offset the ray, keeping it along the XZ plane of the hit
Vector3 offsetDirection = -1 * hit.normal;
//offset a long way, minimum thickness of the object
ray.origin = hit.point + offsetDirection * 100;
//point the ray back at the first hit point
ray.direction = (hit.point - ray.origin).normalized;
Replace:
//raycast all, because there might be other objects in the way
RaycastHit[] hits = Physics.RaycastAll(ray);
foreach (RaycastHit h in hits)
{
if (h.collider == hit.collider)
{
hitBack = h.point; //destination point
}
}
With (credits to MirrorMirror's insightful post, and #ryemoss for his instrumental advice and assistance):
int counter = 0;
bool calculating = false; //set this to true on click
Vector3 Point, PreviousPoint, Goal, Direction;
Point = ray.origin;
Goal = hit.point;
Direction = ray.direction;
PreviousPoint = Vector3.zero;
while (calculating == true)
{
counter++;
RaycastHit hit2;
if (Physics.Linecast(Point, Goal, out hit2))
{
if(counter > 100)
{
hitBack = hitPoint;
counter = 0;
calculating = false;
break;
}
PreviousPoint = hit2.point;
Point = hit2.point + (Direction / 10000f);
}
else
{
if (PreviousPoint == Vector3.zero)
hitBack = hitPoint;
else
hitBack = PreviousPoint;
calculating = false;
counter = 0;
}
}
Linecast vs Raycast
With a raycast you set the start point, the direction, and the distance to check in that direction, with a linecast you simply set start and end points and it checks between those 2 points.
So, if you know the end destination specifically, use linecast, if you want to check in a specific direction but have no specific end point, use raycast.
Solution
First, use the initial raycast to obtain the first point, hit.point. Then, set the ray.origin to a point in world space outside the collider (the collider of the object we first collided with to obtain hit.point), and set the ray.direction to face the ray back at the first point, hit.point.
Finally, use a while loop to create a new linecast, at ray.origins new position (updated each time through the while loop until a linecast reaches hit.point), each time a collision with the object occurs until a linecast reaches hit.point. Once hit.point has been reached, it means every surface of the object was hit and on each hit, a new line was created until a line reached the first initial point, hit.point. To calculate thickness, take the distance between the first hit, hit.point, and the hit previous to the reverse linecast hitting hit.point, PreviousPoint.
UPDATE
1-Revise the code to properly handle 1-sided objects (ex: Planes).
2-Added counter to prevent special cases in which calculation not possible.
3-Improve readability.