Question by Chelmney_ · Jul 23, 2013 at 09:06 PM · ray circle arm

Rays in relation to the Distance to another point

Hey there,

I'm using a camera.ScreenPointToRay(mouse.Input) ray and I want to adjust it according to another point, the hand of an enemy. Basically, I want the end of the ray to always be reachable by the hand/the arm of the enemy. To do t$$anonymous$$s, I'm calculating the length of $$anonymous$$s arm at the start of the game. Now, my question is: How do I use the length of the arm to figure out where the end of the ray should be? I'm using an IK algorithm and it requires the end point to never be out of reach. I'm having quite a hard time figuring t$$anonymous$$s out here and I'm stuck. T$$anonymous$$nking about it, I'll rephrase my question: How do I get a ray to stay on a circle with a radius of the length of an arm? It should be able to stay inside the circle, but never leave it.

Greetings,

Chelmney

Add comment · Show 3

robertbu · Jul 23, 2013 at 09:13 PM 0

I need a drawing or screen shot to understand the question...to see the relationship of the arm to the mouse position. FYI, I found that the ray returned by ScreenPointToRay() starts at the near clip plane of the camera.

Chelmney_ · Jul 23, 2013 at 09:21 PM 0

alt text

Okay, simply put: How do I move the end point back inside the circle when it leaves it like that? I know how to check when it passes the circle now, but I don't know how to check where I need to place it so it's on a line from the center of the circle to the end point but still on the edge of the circle if that makes sense.

explanation.png (4.2 kB)

robertbu · Jul 23, 2013 at 09:39 PM 0

I'm still fuzzy. This is the second question today that I've struggled conceptually, so it's probably just me. I'm going to guess and make a suggestion. If you go here you will find a script with a library of 3D functions.

http://wiki.unity3d.com/index.php/3d_Math_functions

One of the functions is ProjectPointOnLine(). The 'linePoint' parameter will be your ray.origin. The 'lineVec' parameter will be ray.direction. The 'point' parameter will be the origin of the arm. It will return the closest point on the ray to the origin of the arm. If the point is greater than 'Arm Length' away, it cannot be reached. You can also use that point to calculate the closest point on the circle to the line, therefore moving it back in reach:

 pointOnCircle = (closestPoint - circleCenter).normalized * armLength + circleCenter;

Welcome to Unity Answers

If you’re new to Unity Answers, please check our User Guide to help you navigate through our website and refer to our FAQ for more information.

Before posting, make sure to check out our Knowledge Base for commonly asked Unity questions.

Check our Moderator Guidelines if you’re a new moderator and want to work together in an effort to improve Unity Answers and support our users.

Rays in relation to the Distance to another point

0 Replies

Your answer

Welcome to Unity Answers

Follow this Question

Related Questions