# jagguy2

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1. ## find Y value

how do i get scalar constant? say I am moving over this plane with normalized vec (0, .707, -.707) A(0,0,0) B(200,0,0) C(200,71,71) D(0,71,71) I start at 0,0,0 and I want to move forward 10 along z axis to 10 my x val is =0 but my Y val =?
2. ## find Y value

If I have the normal vector of a rectangular surface and the coordinates of each vertex. Can I work out the Y value of the surface given x,z value? Say I have a right angled triangle shape and the surface I am, talking about is the longest side . Can I find the point on the surface given x and z so I would need to find Y somehow?
3. ## normals to a plane

thanks for the help speaking of just a vector what confuses me is the concept of vector has a direction. It is just a 3D point and we are saying it also points to a direction. how do we know what direction it points at because a point on x,y,z could point in any direction theoretically
4. ## normals to a plane

what has happened is that I am using away3D. z axis has positive values into the screen and negative values out of the screen. so will switching the order in which you do the cross product solve this?
5. ## normals to a plane

(0,-14200,14200) is normal so normalize i get 20081 = normalize factor (0, -.707, .707) now since y value is negative the normal points down but i want it to point up dont I out of the surface?
6. ## normals to a plane

let me see if i have this right i will find the suface that is on a slope for right angled triangle 3d Shape (the longest side). now the slope is at a 45 deg angle . 4 points around this rectangle surface is A(0,0,0) B(200,0,0) C(200,71,71) D(0,71,71) V1 vector1= B - A (200,0,0) V2 vector2=C - A (200,71,71) cross product vector1 X vector2 cross product x= v1.y X v2.z - v1.zX v2.y = 0X71 - 71X0= 0 cross product y= - (( v2.z X v1.x) - (v2.x X v1.z)) = - 71X200 -0= -14200 cross product z= v1.x X v2.y - v1.y X v2.x= 14200 (0,-14200,14200) is normal is this correct?
7. ## normals to a plane

hi, I have a 3D shape which is a right angles triangle shape. Like a bike ramp. I have an object that moves up the ramp. What I need to know is given an x,y,z point how do i know if this point will be inside or outside this 3D object. I really need to know if this point is just touching the ramp. maybe easiest to see the mathematics
8. ## straight line collisions

here is my worked example say I have 2 endpoints of a line x1(10,10,10) and x2(10,10,20) and i have a point x0(15,10,15). I want to know distance of the point x0 from the line x1 to x2 from 10) http://mathworld.wolfram.com/Point-LineDistance3-Dimensional.html d=(5,0,-5)X(5,0,-5) / (0,0,10) cross product numerator http://en.wikipedia.org/wiki/Cross_product gives (0,50,0)/(0,0,10) and now what because I need a single value?
9. ## straight line collisions

It is a 3D collision but on a x/z axis the missile moves a certain amount of pixels per frame. I can collide by simply calculating the postion of the missile and object to hit. I am not sure what you mean by your 2) although it sounds interesting. basically I have 2 points in x,y,z space which is the missile line. I have a point eg middile of object to hit. I need to caculate the how close this point is to the line
10. ## straight line collisions

I have a 3D game where I shoot a missile forward about 200px at a time. some objects in the missile path are smaller than 200px wide. I can test for collisions every 50px but is there another algorithm to I could use?
11. ## repeating background

I am not seeing how this works exactly. the texture could go over all the shapes and only a few parts of the trach should be displayed at once and then keep swapping? each part of the track has its own texture in place. This is what I rrad.
12. ## repeating background

In 3D how do you do repeating backgrounds? The issues of displaying a road for example in a car race (just straight head track with a few curves. NOt a loop.
13. ## 3D camera clipping

I am using away3D and actionscript3. What are the 3D concepts where objects are clipped/not clipped when out of view. I am having problems finding this for away3D. MY issue is when I move the camera forward , objects move behind me and out of view. If an object is only partly displayed (1/3 in view) it seems to just vanish when the camera is moved forward without displaying the rest of the image.
14. ## 3D camera

moved beginner
15. ## 3D collisions

I am still confused about how ray plane intersection works for 3D objects like a missile and building or walking into a solid object. I am needed it for a computer game but i prefer to understand the mathmatics first. I think the issue is that I need an example with real coodinates.