Re: Reflecting a ray off a line

"Dieter Hansen" <dieter.hansen@[EMAIL PROTECTED]
> wrote in message 
news:473f064c$1@[EMAIL PROTECTED]
> Richard schrieb:
>> I'm absolute beginner to computer graphics. I'm just seeking hints to
get 
>> a
>> feel for the nature of the task. I'm talking about 2D graphics. I'm not

>> seeking someone to do the task for me.
>>
>> Lets say there is a line (line segment) and I wanted to get the
computer 
>> to
>> draw a ray that reflected off the line at the angle of incidence to the
>> line. Like a light ray hitting a flat mirror.
>>
>> In just basic terms, what is required enabling the computer to end the 
>> ray
>> at the line intersection, and then draw another line segment (that 
>> continues
>> the ray), starting from the intersection and in the proper direction?
>>
>
>
> 1. define your line segment (most likely using point1 and point2)
> 2. define your ray (most likely using an origin and a direction)
> 3. calculate the intersection point between line segment and ray
> 4. create 2nd ray (the reflection ray)
> a. with the calculated intersection point as origin
> b. the direction can be calculated using the law of reflection
>    (basically this equation R = 2 · N ·(N dot -D)+D ; where R is the new

> direction, N the normal of the line segment and D     the incoming ray 
> direction)
>
>
> **** till here this is all mathematically and no drawing involved ****
>
> 5. draw your line segment
> 6. draw the first ray from its origin to the intersection point
> 7. draw the second ray from its origin to an arbitrary point in the ray
>
> Regards
> Dieter

Dieter
Thanks.

I was just beginng to discover about use of the Normal in computing a 
reflected ray.

I will take your (sort of) algorithm (points 1-7) and flesh it out.

I'm hoping that I can produce a simple programme using Virtual Basic or
C#, 
employing the function/methods associated with Microsoft's  .NET library.

I was actually wondering whether "Drawlines" in the .NET library might
have 
been of use rather than "Drawline". I'll try to figure things out the best
I 
can given the steps you mention. I may ask one or two more questions
before 
I'm done. :c)

Rich