Hi guys,

I'm currently doing a fan-fic of Sonic the Hedgehog. As you probably know, Sonic is able to run enormously FAST and capable of running up walls, ceilings, loopings and so on. I've got the gravity in place, the overall movement is up and running, but I need to get the TILT and ROLL angles right for my model, because its feet are supposed to face the ground at any time, even while running in a looping (so at the highest point of a looping, the model is supposed to be upside-down, when running up a wall, feet, body and head should be aligned in a horizontal manner instead of a vertical and so on).
So, I had a look at the c_trace-command. It modifies the "target" vector and the "normal" vector, the latter giving us the normal of the hit surface (therefore the normal of the surface we are currently walking/running on). The question is: how do I convert the normal vector of the surface the model is currently walking on into tilt and roll angles so that Sonics feet point towards the ground?

Greets and thanks in advance!


Alan

I think 'vec_to_angle' is what you want.

i think c_trace and normal vector + vec_to_angle is what you want.

It seems to be quite a popular problem these days. I just put up a contribution under "Lite-C Contributions" that should help you out.

It's a function that takes an angle and two vectors (one from the world -- using "normal" after c_trace or c_move makes sense -- and one local vector that you want to align with the world one -- using "vector(0, 0, 1)" will make Sonic's feet line-up on the surface underneath him), and modifies the angle so that it lines up.

It doesn't use vec_to_angle.

Jibb

@DJBMASTER&Quadraxas: I already tried to use vec_to_angle in combination with c_trace. The main problem is that "vec_to_angle" outputs *pan* and *tilt* angles. The pan-angle, however, is controlled by the player (left/right cursor keys) and determines the direction Sonic is moving at. What I need is to get tilt and roll correct instead of pan and tilt, see the difference? So getting the right tilt angle is no problem at all, but the roll-angle causes enormous problems.

@JulsMighty: Okay, that sounds just like the function I need. But yet I do not fully understand all parameters. The angle is clear, the first vector (world coordinates) is clear as well, but what about that local vector? What meaning does it have and where do I get it from? Or is it just *always* (0,0,1) if I want Sonic's feet to face the surface underneath them?

It allows the function to be more general:

It will *always* be (0, 0, 1) if you want Sonic's feet to face the surface underneath them (that is, the function will line up Sonic's "up" with the surface normal). If you use (1, 0, 0), Sonic's back will line up with the surface you c_trace, since it'll line up Sonic's local x-axis with the surface normal (this would be similar to "vec_to_angle", except the roll won't necessarily be zero, since only the smallest rotation possible is done to line the angle up).

Don't forget to rotate Sonic's pan relative to his current orientation (using ang_rotate or c_rotate(..., USE_AXIS)) instead of just adding or subtracting to his pan.

Jibb

@JulzMighty: Oh, I see, now I get the hang in it! I will definitly try your function tomorrow, sounds really great, logical and easy to use. Thanks for your explanation

Greets and thanx


Alan

Well, I have a similar problem and I did not actually get it. I have a vehicle and a terrain with hills and slopes. I want to make this vehicle always stay perpendicular to the surface. I tried to use c_trace and vec_to_angle and normal but the vehicle looks with its x axis to the surface instead of z axis. So how can I make the vehicle be always perpendicular to the surface at an angle or slope of the terrain?
Thanks.

Hi not sure if this helps as Im getting back into GS after a hiatus of a year so I cannot guarantee it works now. This is some old code not made by me that works after a trace. Basically this can be converted to contain changes to the roll as it only currently converts the tilt of the surface to the player. The my.tilt += 0.1....is there to smoothly change the the tilt angle of the player.

Hope this helps...


temp.tilt = 0;
temp.roll = 0;
temp.pan = -my.pan;
vec_rotate(normal, temp);
temp.tilt = -asin(normal.x);
my.tilt += 0.1 * ang(temp.tilt - my.tilt); // play with 0.1
my.roll = 0;

Thanks Tiger Tao, I added this line "my.roll += 0.1* ang(temp.z - my.roll); " to the code and now the angles are adjusted as they should. Though I do not think that I will use it now.... I am "playing" with my.tilt values but still can't make the movement be smooth enough. I think this code is perfect for human movements or some other objects, but not for vehicles. So, I will definitely use it, but for other purposes. The bad thing is that I do not yet understand the math behind this script, I need time to figure it out. Thank you anyways.