CdeathJd wrote:
> [...]
> I have no idea how to grab the x,y,z value from the camera, or the
> spline. I failed here in basic aswell, but cant really explain why,
> and that wasnt using splines at all.
> 
> I tried doing this in the camera statement:
>       Spline_Trans (MySpline, clock-1, y, 0.85, 0.85)
>       //translate <50, 42.5, -212>
>       #declare ythen=y;
>       Spline_Trans (MySpline, clock, y, 0.85, 0.85)
>       #declare ynow=y;
> 
> it didnt error, but the camera then went far to the left of the track,
> even if by chance, the "ythen" and "ynow" values worked, and the view
> didnt shift to the left, i still wouldn't know what to do next. Its a
> shame it doesnt work more like other programming languages! Then it
> would have been easier :S

OK, I'll try to help you.  Try the following:

If you already have declared a spline (called Track here), you can alway
obtain a point from it at a given time by insetring

  Track(time)

So, if you want to know, where you are in this frame, simply take the
clock as time.

  Track(clock)

gives you the point where you are. If you want to find out, in which
direction you have to look, simply get The position on the track a
second later:

  Track(clock+1)

So you first have to declare the spline Track. Afterwards, you can add
the camera to your scene.

  camera {
    location Track(clock)
    look_at Track(clock+1)
  }

You can of course also use Spline_Trans. This would look like

  camera {
    location <0,0,0>
    look_at <0,0,1>
    Spline_Tans(Track, clock, y, 0.85, 0.85)
  }

One call of Spline_Trans does actually exactly what I discribed: It
computes the location using the clock as time and another point using
clock+0.85.

Note on the camera: You can position and align a camera wich the
location and look_at. But can also rotate and translate a camera
afterwards by using rotate and translate.

If you need more help, just ask.

(If you not already have done so, take a look at the following sections
in the doc: 2.2.1.9, 2.7.18 (I'm referring to the online documentation
http://www.povray.org/documentation/))

Greetings
Urs

Post a reply to this message

To all,

Cheers for all your help people, i finally got it working today, it was done
in a stange way indeed but i managed to make it work. Thanks to everyone for
their advice and for putting up with my defeatism, im a pessimist im afraid.
However doing a lot of research helped me get there in the end.

For reference, here is the file as it currently stands. Hopefully if others
run into similar problems this will help them out. Note that the file does
not depend on the CLOCK value in any way:

// Persistence of Vision Ray Tracer Scene Description File
// File: This.pov
// Vers: 3.6
// Desc: Roller Coaster Tycoons match
// Date: cant remember
// Auth: Cdeath, with a LOT of help from others!
//

#declare Powered_Launch=0;              // Powered Launch? 1=Yes 0=no, -
this means that a certain increase in velocity happens up to a frame
threshhold
#declare Powered_Launch_Add=0.02;       // velocity to add each frame
#declare Powered_Launch_Clock=0;        // Stop adding when CLOCK reaches
this value

#declare velocity=0.2;
#declare ynowvel=0;
#declare SPLINE_POINTS=215;
#declare SPLINE_POINTS=SPLINE_POINTS-1;


#macro Save_Velocity()
  #fopen IFV_File "InterFrameVelocity.inc" write
  #write ( IFV_File, "// This is a generated file which " )
  #write ( IFV_File, "can probably be deleted without too much harm.n" )
  #write ( IFV_File, concat(  "#declare ynowvel = ", str(ynowvel,0,3),";n"
))
  #write ( IFV_File, concat(  "#declare velocity = ", str(velocity,0,3),";n"
))

  #fclose IFV_File
#end

// VERY IMPORTANT!!!

//Save_Velocity()

//De-commenting the above line will reset the simulation, and create file
"InterFrameVelocity.Inc"
//Once this has done, and pov-ray starts to render, stop the render and
re-comment the line, other
//wise the camera wont go anywhere.



#version 3.6;

#include "math.inc"
#include "transforms.inc"
#include "colors.inc"
#include "InterFrameVelocity.inc"


global_settings {
  assumed_gamma 2.0
  max_trace_level 3
}


// ----------------------------------------


#declare MySpline =
spline {
   natural_spline

-2, <-1.04587,-0.2,11.9543>,
-1, <-1.83027,-0.2,20.9201>,
0, <-2.61467,-0.2,29.8858>,
1, <-3.39907,-0.2,38.8516>,
2, <-4.18348,-0.2,47.8173>,
3, <-4.96788,-0.2,56.7831>,
4, <-5.75137,-0.492935,65.7384>,
5, <-6.51985,-2.23882,74.5222>,
6, <-7.24984,-5.50099,82.866>,
7, <-7.9188,-10.1788,90.5123>,
8, <-8.50608,-16.1277,97.2249>,
9, <-8.99354,-23.1641,102.797>,
10, <-9.36615,-31.0709,107.056>,
11, <-9.61977,-39.5802,109.954>,
12, <-9.88797,-48.0347,113.02>,
13, <-10.2199,-56.1862,116.814>,
14, <-10.6129,-63.9717,121.306>,
15, <-11.064,-71.3309,126.462>,
16, <-11.5697,-78.2069,132.242>,
17, <-12.1261,-84.5466,138.602>,
18, <-12.7289,-90.301,145.492>,
19, <-13.3735,-95.4254,152.859>,
20, <-14.0547,-99.8804,160.646>,
21, <-14.7675,-103.631,168.793>,
22, <-15.5062,-106.65,177.237>,
23, <-16.2652,-108.911,185.912>,
24, <-17.0385,-110.399,194.751>,
25, <-17.8203,-111.102,203.687>,
26, <-18.6044,-111.014,212.649>,
27, <-19.3848,-110.136,221.569>,
28, <-20.1555,-108.475,230.378>,
29, <-20.9104,-106.043,239.007>,
30, <-21.6676,-102.853,247.385>,
31, <-22.6483,-98.8524,255.383>,
32, <-23.8709,-94.0639,262.9>,
33, <-25.2839,-88.5351,269.854>,
34, <-26.8283,-82.322,276.174>,
35, <-28.4385,-75.4874,281.797>,
36, <-30.044,-68.1001,286.674>,
37, <-31.5708,-60.2348,290.765>,
38, <-33.3106,-52.3151,294.66>,
39, <-35.7494,-44.8479,299.044>,
40, <-38.9568,-37.904,303.778>,
41, <-42.9761,-31.5492,308.715>,
42, <-47.8225,-25.8437,313.701>,
43, <-53.4827,-20.8416,318.584>,
44, <-59.9155,-16.5903,323.215>,
45, <-67.0528,-13.1301,327.455>,
46, <-74.8025,-10.4938,331.181>,
47, <-83.0509,-8.7063,334.288>,
48, <-91.6674,-7.78466,336.695>,
49, <-100.508,-7.73755,338.344>,
50, <-109.422,-8.56543,339.208>,
51, <-118.254,-10.2605,339.285>,
52, <-126.853,-12.8066,338.602>,
53, <-135.26,-15.6802,337.182>,
54, <-143.536,-18.4732,335.021>,
55, <-151.614,-21.1856,332.133>,
56, <-159.43,-23.8169,328.537>,
57, <-166.921,-26.367,324.255>,
58, <-174.026,-28.8357,319.318>,
59, <-180.688,-31.2226,313.762>,
60, <-186.874,-33.4516,307.621>,
61, <-192.614,-35.2148,300.921>,
62, <-197.849,-36.4766,293.714>,
63, <-202.521,-37.2327,286.063>,
64, <-206.578,-37.4808,278.038>,
65, <-209.981,-37.2202,269.714>,
66, <-212.697,-36.4515,261.172>,
67, <-214.709,-35.1755,252.496>,
68, <-216.004,-33.2985,243.794>,
69, <-216.588,-30.7776,235.179>,
70, <-216.484,-27.6265,226.754>,
71, <-215.73,-23.8622,218.618>,
72, <-214.379,-19.5054,210.864>,
73, <-212.498,-14.5798,203.575>,
74, <-210.165,-9.11214,196.822>,
75, <-207.571,-3.69689,190.136>,
76, <-205.208,-0.014575,182.297>,
77, <-203.369,1.65415,173.671>,
78, <-202.233,1.21706,164.777>,
79, <-201.851,-1.30167,156.169>,
80, <-202.151,-5.76286,148.384>,
81, <-202.941,-11.92,141.897>,
82, <-203.937,-19.3871,136.999>,
83, <-204.931,-26.9988,132.302>,
84, <-205.892,-34.3841,127.25>,
85, <-206.805,-41.5275,121.854>,
86, <-207.655,-48.4142,116.123>,
87, <-208.427,-55.03,110.072>,
88, <-209.106,-61.3611,103.713>,
89, <-209.679,-67.3945,97.0602>,
90, <-210.121,-73.3661,90.3428>,
91, <-210.41,-79.7202,83.9775>,
92, <-210.559,-86.4431,77.998>,
93, <-210.584,-93.5109,72.4284>,
94, <-210.502,-100.898,67.2908>,
95, <-210.332,-108.579,62.6056>,
96, <-210.093,-116.526,58.3906>,
97, <-209.802,-124.695,54.6272>,
98, <-209.445,-132.916,50.9812>,
99, <-209.016,-141.148,47.369>,
100, <-208.517,-149.392,43.7919>,
101, <-207.949,-157.646,40.2514>,
102, <-207.314,-165.913,36.7487>,
103, <-206.613,-174.19,33.2852>,
104, <-205.846,-182.478,29.8622>,
105, <-204.958,-190.67,26.2467>,
106, <-203.865,-198.612,22.1603>,
107, <-202.553,-206.274,17.6261>,
108, <-201.008,-213.623,12.6691>,
109, <-199.22,-220.632,7.3168>,
110, <-197.178,-227.273,1.59809>,
111, <-194.876,-233.519,-4.45632>,
112, <-192.297,-239.307,-10.8436>,
113, <-189.37,-244.357,-17.6882>,
114, <-186.096,-248.572,-24.9295>,
115, <-182.499,-251.903,-32.4721>,
116, <-178.61,-254.31,-40.2178>,
117, <-174.465,-255.765,-48.0679>,
118, <-170.11,-256.252,-55.9239>,
119, <-165.596,-255.764,-63.6894>,
120, <-160.94,-254.828,-71.3344>,
121, <-156.131,-253.864,-78.8802>,
122, <-151.171,-252.871,-86.3237>,
123, <-146.061,-251.851,-93.6617>,
124, <-140.804,-250.803,-100.891>,
125, <-135.403,-249.726,-108.009>,
126, <-129.86,-248.622,-115.013>,
127, <-124.177,-247.489,-121.899>,
128, <-118.357,-246.329,-128.665>,
129, <-112.403,-245.14,-135.308>,
130, <-106.317,-243.923,-141.825>,
131, <-100.101,-242.679,-148.214>,
132, <-93.7597,-241.406,-154.472>,
133, <-87.2944,-240.105,-160.596>,
134, <-80.7086,-238.777,-166.585>,
135, <-74.005,-237.42,-172.434>,
136, <-67.1867,-236.036,-178.143>,
137, <-60.2566,-234.623,-183.709>,
138, <-53.2179,-233.183,-189.129>,
139, <-46.0736,-231.715,-194.402>,
140, <-38.827,-230.219,-199.525>,
141, <-31.4812,-228.695,-204.496>,
142, <-24.0395,-227.143,-209.314>,
143, <-16.5051,-225.563,-213.976>,
144, <-8.94393,-223.808,-218.529>,
145, <-1.44341,-221.693,-223.031>,
146, <5.98382,-219.223,-227.472>,
147, <13.3252,-216.402,-231.846>,
148, <20.5682,-213.235,-236.147>,
149, <27.7006,-209.726,-240.366>,
150, <34.7103,-205.881,-244.498>,
151, <41.5853,-201.708,-248.536>,
152, <48.3138,-197.212,-252.474>,
153, <54.8843,-192.402,-256.306>,
154, <61.2855,-187.286,-260.025>,
155, <67.5064,-181.871,-263.627>,
156, <73.5362,-176.168,-267.105>,
157, <79.3646,-170.185,-270.455>,
158, <84.9814,-163.932,-273.672>,
159, <90.3769,-157.421,-276.751>,
160, <95.5415,-150.661,-279.687>,
161, <100.466,-143.664,-282.477>,
162, <105.143,-136.443,-285.116>,
163, <109.562,-129.007,-287.601>,
164, <113.717,-121.371,-289.929>,
165, <117.6,-113.547,-292.096>,
166, <121.203,-105.548,-294.1>,
167, <124.522,-97.3876,-295.939>,
168, <127.656,-89.1278,-297.656>,
169, <130.806,-80.8662,-299.337>,
170, <133.974,-72.6047,-300.983>,
171, <137.16,-64.3431,-302.595>,
172, <140.363,-56.0816,-304.171>,
173, <143.584,-47.82,-305.712>,
174, <146.821,-39.5584,-307.217>,
175, <150.075,-31.2969,-308.687>,
176, <153.345,-23.0353,-310.121>,
177, <156.63,-14.7737,-311.518>,
178, <159.93,-6.51214,-312.88>,
179, <163.245,1.74943,-314.205>,
180, <166.575,10.011,-315.494>,
181, <169.918,18.2726,-316.746>,
182, <173.275,26.5341,-317.961>,
183, <176.646,34.7957,-319.139>,
184, <180.028,43.0573,-320.28>,
185, <183.424,51.3189,-321.384>,
186, <186.831,59.5804,-322.45>,
187, <190.25,67.842,-323.479>,
188, <193.68,76.1035,-324.47>,
189, <197.12,84.3651,-325.423>,
190, <200.571,92.6266,-326.339>,
191, <204.032,100.888,-327.216>,
192, <207.502,109.15,-328.056>,
193, <210.981,117.411,-328.857>,
194, <214.469,125.673,-329.62>,
195, <217.965,133.935,-330.344>,
196, <221.468,142.196,-331.03>,
197, <224.979,150.458,-331.677>,
198, <228.497,158.719,-332.286>,
199, <232.022,166.981,-332.856>,
200, <235.552,175.243,-333.387>,
201, <239.088,183.504,-333.88>,
202, <242.629,191.766,-334.333>,
203, <246.175,200.027,-334.748>,
204, <249.726,208.289,-335.123>,
205, <253.28,216.551,-335.46>,
206, <256.838,224.812,-335.757>,
207, <260.399,233.074,-336.015>,
208, <263.962,241.335,-336.234>,
209, <267.528,249.597,-336.414>,
210, <271.095,257.858,-336.555>,
211, <274.664,266.12,-336.656>,
212, <278.234,274.381,-336.718>,
213, <281.804,282.643,-336.741>,
214, <285.374,290.904,-336.724>,
215, <288.944,299.166,-336.669>,


}

// First-person-view camera
// Follows the same path as the first aircraft


#declare ynowvel=ynowvel+velocity;
#if (Powered_Launch=1)
    #if (clock<Powered_Launch_Clock)
        #declare velocity=velocity+Powered_Launch_Add;
    #end
#end
#declare VECT_HERE=MySpline(ynowvel).y;
#declare VECT_THERE=MySpline(ynowvel+velocity).y;

// Physical Velocity stuff
#if (VECT_HERE>VECT_THERE)
        #declare velocity=velocity+0.006;
#end
#if (VECT_HERE<VECT_THERE)
        #declare velocity=velocity-0.005;
#end

Save_Velocity()

   camera {
      location 0//<-150,-22.5, 140>
      //look_at z
      //look_at <-150,-32.5, 60>
      translate <0,0.4,0.4>
      Spline_Trans (MySpline, ynowvel, y, 0.85, 0.85)
      Save_Velocity()
      //translate <50, 42.5, -212>
      //Spline_Trans (MySpline, clock, y, 0.85, 0.85)

   angle 30
   }

  light_source {
  <0, 1, 0>            // light's position (translated below)
  color rgb <1, 1, 1>  // light's color
  Spline_Trans (MySpline, ynowvel, y, 0.5, 0.5)

  fade_distance 5
  fade_power 1
}



//camera {
//  location  <140.0, 44.0, 185.0>
//  look_at   <140.0, -50.0, 220.0>
//}

union {
   #declare C = 0;
   #declare Cmax= SPLINE_POINTS;
   #while (C<=Cmax)
      #declare Value1 = C/Cmax*SPLINE_POINTS;
      #declare Value2 = (C+1)/Cmax*SPLINE_POINTS;
      #declare Point1 = -0.5*y+MySpline(Value1);
      #declare Point2 = -0.5*y+MySpline(Value2);
      sphere {Point1, 0.2}
      cylinder {Point1, Point2, 0.16}
      #declare C = C+1;
   #end
   pigment {color rgb 0.5}
   finish {reflection 0.6 specular 2.5}
   //translate <50, 42.5, -230>

}

difference {
box {
  <-3000, -3000, -3000>  // one corner position <X1 Y1 Z1>
  < 3000,  3000,  3000>  // other corner position <X2 Y2 Z2>
}
union {
   #declare C = 0;
   #declare Cmax= SPLINE_POINTS;
   #while (C<=Cmax)
      #declare Value1 = C/Cmax*SPLINE_POINTS;
      #declare Value2 = (C+1)/Cmax*SPLINE_POINTS;
      #declare Point1 = -0.5*y+MySpline(Value1);
      #declare Point2 = -0.5*y+MySpline(Value2);
      //cylinder {Point1-0.1, Point2+0.1, 4.16}
      #declare C = C+1;
      box{ <-5,-5,-5> <5,5,5> translate Point1
         pigment {color rgb<1.0,0.7,0>} }
   //normal {dents 0.8 scale 0.45}}
   #end

   //finish {reflection 0.6 specular 2.5}
   //translate <50, 42.5, -230>

}}
// END OF FILE
I plan to add a "chain mechanism" as the rollercoaster doesn't roll
backwards at all. i Think i may be getting the hang of a lot of things now.

Does anyone have any advice on this issue, now that you've proved me wrong
reguarding the subject title?

For those that want a look at the finished product, a short movie clip (4MB)
can be downloaded here:
http://209.245.59.241/Gimme/66413073/1605450461/107060564/%7B5DA6D5F4-BCC8-4F91-B026-319609B6CD3A%7D/0.216928/2/Velocit
yTest.avi

Post a reply to this message

CdeathJd nous apporta ses lumieres en ce 01/08/2006 21:22:
> Also i tried the only other thing i could think of, making pov ray calculate
> through each frame, from the beginning adding the velocity if it was facing
> downwards, this didn't work, gave an error, and stopped letting me render
> untill i reloaded the program, no idea why, heres my attempt at it:

>    camera {
>       location 0
>       look_at z
>       translate <0,0.4,0.4>

>       #declare clock1=0;
>       #declare newy=0;
>       #declare oldy=0;
>       #declare velocity=1;
>       #while (clock1<clock)
>                 #declare oldy=newy;
>                 Spline_Trans (MySpline, velocity+(clock*130), y, 0.5, 0.5)
>                 #declare newy=camera.y;
>                 #if (newy>oldy)
>                         velocity=velocity+0.5;
>                 #end
>                 #declare clock1=clock1+1;
>       #end


>    }


By default, the clock variable goes from 0 to 1. As clock1 increase by steps of 
1 unit, the loop will always exit the first time trough, even on the very last 
frame where clock will be equal to 1.
As a side note: variables are case sensitive: "A" is distinct from "a". It's 
always preferable to use user variables starting with an upper case character. 
That way, if the SDL gets later expanded, you can be sure that your variables 
names won't conflict with any new reserved words.

-- 
Alain
-------------------------------------------------
A pat on the back is only a few centimeters from a kick in the butt.

Post a reply to this message

CdeathJd nous apporta ses lumieres en ce 06/08/2006 15:25:
> Urs Holzer <urs### [at] andonyarcom> wrote:
>> Just evaluate the spline at two times. Once where you are in time now
>> and once a second later. This gives you the position you have now and
>> the position you will have a second later. If you substract these two
>> values you will have the velocity. (The velocity is a vector pointing
>> in the direction you move. His length is your speed.)
>>
> 
> This would be good to do, if its gone down, add some velocity, but im too
> used to basic and i cant do it in pov-ray, its two different languages, the
> only similarity is the maths.
> 
> I have no idea how to grab the x,y,z value from the camera, or the spline. I
> failed here in basic aswell, but cant really explain why, and that wasnt
> using splines at all.
> 
> I tried doing this in the camera statement:
>       Spline_Trans (MySpline, clock-1, y, 0.85, 0.85)
>       //translate <50, 42.5, -212>
>       #declare ythen=y;
>       Spline_Trans (MySpline, clock, y, 0.85, 0.85)
>       #declare ynow=y;
> 
> it didnt error, but the camera then went far to the left of the track, even
> if by chance, the "ythen" and "ynow" values worked, and the view didnt
> shift to the left, i still wouldn't know what to do next. Its a shame it
> doesnt work more like other programming languages! Then it would have been
> easier :S
> 
> 
> 
You could alter your speed acording to your hight, usualy represented by the "y" 
coordinate. You go faster when you are low, smaller y values, and slower when 
high, larger y values.

-- 
Alain
-------------------------------------------------
Gossip is when you hear something you like about someone you don't.

Post a reply to this message

CdeathJd nous apporta ses lumieres en ce 07/08/2006 18:21:
> To all,
> 
> Cheers for all your help people, i finally got it working today, it was done
> in a stange way indeed but i managed to make it work. Thanks to everyone for
> their advice and for putting up with my defeatism, im a pessimist im afraid.
> However doing a lot of research helped me get there in the end.
> 
> For reference, here is the file as it currently stands. Hopefully if others
> run into similar problems this will help them out. Note that the file does
> not depend on the CLOCK value in any way:
> 

> //Save_Velocity()
Use the following instead, and you don't have to stop/restart the rendering.

#if(frame_number = 1) Save_Velocity() #end

On the first frame, the condition is true and the code is executed.
On any other frame, the condition is false and the code is completely skipped.

NO more need to comment out/uncomment :-)

Great tool during scene creation to. Using #if(Flag), Flag been deffined near 
the top of the scene, or #if(1) #if(0) allows you to very easily enable or 
disable part of your code, like temporarily removing some object, texture 
elements or just about anything you may need to.


-- 
Alain
-------------------------------------------------
Fundamentalism: Shit must be born again.

Post a reply to this message

Alain <ele### [at] netscapenet> wrote:
> Use the following instead, and you don't have to stop/restart the rendering.
>
> #if(frame_number = 1) Save_Velocity() #end
>
> On the first frame, the condition is true and the code is executed.
> On any other frame, the condition is false and the code is completely skipped.
>
> NO more need to comment out/uncomment :-)
>
> Great tool during scene creation to. Using #if(Flag), Flag been deffined near
> the top of the scene, or #if(1) #if(0) allows you to very easily enable or
> disable part of your code, like temporarily removing some object, texture
> elements or just about anything you may need to.

Thanks, i initially tried something like that but i used a variable insted.

Another problem, although not a killer one, is that if the track is pointing
directly up or down, and turns a bit, say like a loop-the-loop, the camera
"flips" over, onto the top of the track, when, naturally it should just
remain underneath.
If anyones got any tips on getting rid of this side-effect i'd be most
gratefull, like i said though, its not a killer of a problem.

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Also, is it possible to get predifined track "sections" to work. I had a
ready-made section, but it doesn't rotate it to be aligned, it places the
track pieces correctly, but they all face the same way,

Any advice would be nice, as im still using a tube and its looking a lot
like a monorail rollercoaster, than one on tradition two tracked ones.

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> Any advice would be nice, as im still using a tube and its looking a lot
> like a monorail rollercoaster, than one on tradition two tracked ones.

I was thinking about this. There used to be a nice file Stricia, I still
have it around, but it ran on 3.1g, it would extrude shapes along a 
"spline",
this was before spline was implemented, it worked on arrays.
It's all commented in French, not sure what does what inside ...

There is a small ExtrudeSpline file at
www.oyonale.com/ressources/english/sources09.htm
but it also works with arrays, and doesn't seem to bend the shape to
follow the path.

So I stayed up late last night and wrote some macros to extrude splines, and
manage large splines.

I ended up with...

#declare Path_Spline = Spl_coaster;
#declare Shape_Spline = Spl_Ibeam;
union {
   Extrude_Spline(24, 200, y, 0.01, 0.01)
}

to extrude a shape along a spline from 0 to 1, the splines need to be passed
as declares or else large amounts of memory are used up trying to create
temporary splines. The parameters are the shape-steps, path-steps,
sky-vector, look-forward, and banking. This is the same as Rune's
Spline_Trans macro in transforms.inc, and returns a mesh.

I also added...

VSpline_Trans_Path (Vect, Time, Sky, Foresight, Banking)
which is the same as Spline_Trans, except it returns a vector translated
along Path_Spline, and ...

VMatrix_Trans(vec, A, B, C, D)
which is the same as Matrix_Trans, but returns a vector.

I also did some spline managing to convert the path to 0-1 and control 
points

Remap_Spline(SplA SplB begin_at stop_at rez stype begin_out stop_out)
makes a new spline with different spacing

Save_Spline(SplA SplB Filename begin_at stop_at rez stype)
saves a spline to a file

/*
Remap_Spline(Cdeaths, "Spl_coaster", -2, 215, 1,
   "natural_spline", -1/215, 1+(1/215) )
Save_Spline(Spl_coaster, "Spl_coaster", "coaster_spline.inc",
   -0.0025, 1.0025, 0.0025, "natural_spline" )
*/
#include "coaster_spline.inc"

I'll put the files in p.b.scene_files, they're not completely cleaned up,
but it should get you where you want to go.

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"Tim Attwood" <tim### [at] comcastnet> wrote:

> #declare Path_Spline = Spl_coaster;
> #declare Shape_Spline = Spl_Ibeam;
> union {
>    Extrude_Spline(24, 200, y, 0.01, 0.01)
> }
>

I tried that and it errored, there were not enough parameters, 5 given, 8
expected, i looked at the extrude file, but its all gibberish to me,
however the comments helped a little bit, but when i ran it, where it says

// usage :
object{ExtrudeSpline(nseg,nseg,Shape,Path,doSmooth,doTest,doFile,fname)
texture{pigment{Red} finish {phong 1}}}

i put my declared shape where "shape" is supposed to go and the Spline where
"path" is supposed to go, but it says it was expecting an array.

I tried using two "monorail" splines and offseting them by adding

"#declare Point1 = (-0.5*y+1*x)+MySpline(Value1);" but at every turn the
tubes crossed over, so that didnt work.

Everything you put after what u quoted above means nothing to me... I dont
have a PHD in maths, which it seems you need to have to use povray for
complex stuff.

It doesn't matter though, i could get my track making program perhaps to
make a spline for the left rail, a spline for the right rail, a spline
inbetween for some wooden "staples" but this would involve 3 seperate
splines, possibly with as much as 6000 points in each one. Surely theres an
easier way.

Also i could make the program output the spline (which the camera would use)
and also the location AND ROTATION of each left rail, right rail, staple
etc. That would be a completely stupid amount of objects though!

I'm close to giving up once again, at least i know that the fault is mine
for not being superb at maths. I'm pretty good at it, just not trigonometry
(which i cannot understand).

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> // usage :
> object{ExtrudeSpline(nseg,nseg,Shape,Path,doSmooth,doTest,doFile,fname)

I think this is a simple bit of confusion, the sample I posted doesn't use
"extspln.pov", which I linked in my message, it uses "spline_tools.inc",
which I posted as a binary to povray.binaries.scene_files, along with the
whole example file, "roller_coaster2.pov"

Since then I've added a few more macros to "spline_tools.inc",

Extrude_Spline_To_File
Spline_Translate
Spline_Rotate
Spline_Scale

Since you want to do an animation, extrude the spline to a file
as a mesh, then include the mesh, instead of recalculating the extrude
every frame. I'll post them as well.

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