Hello,

I've tried my very best to ensure that this isn't my code at fault. I posted this issue to the "Starting with Gamestudio" forum before copying it here. I created a level that can be used to reproduce the bug, which I'll link to below. I've spent most of three days researching it. Hopefully it's a bug, or I'll be very embarrassed! :-) I'm using 7.06.

Here's what's up. When doing a c_move, my entity sometimes gets "stuck" where concave blocks intersect.

I'll reiterate my process from my original post:

Step 1: Create a block



Step 2: Copy the block so that I have a grid of 9 blocks



Step 3: Convert each block to a concave block



Step 4: Rise up one corner of one of the triangles



Step 5: Rise up more corners of the surrounding triangles to create a "bump"



Step 6: Attempt to walk on the bump. Get stuck often.



I seem to get stuck where the blocks meet. Here's a screen capture of one of the positions my entity has gotten stuck at:




When I say that the entity is getting stuck, I mean that attempting to move the entity using c_move doesn't work. I added logging to my script that prints out the entity's position and movement vectors. The code:

Code:

---

// Move the player
distance_moved = c_move(me, move_to_vector, nullvector, GLIDE|IGNORE_SPRITES|IGNORE_PASSABLE);

if (key_z)
{
	diag_var("\nx: %6.3f",my.x);
	diag_var("\ny: %6.3f",my.y);
	diag_var("\nz: %6.3f",my.z);
	diag_var("\ndistance to ground: %6.3f",distance_to_ground);
	
	diag_var("\nmove to x: %6.3f",move_to_vector.x);
	diag_var("\nmove to y: %6.3f",move_to_vector.y);
	diag_var("\nmove to z: %6.3f",move_to_vector.z);
	diag_var("\ndistance moved: %6.3f", distance_moved);
	diag_var("\nin solid: %6.3f",in_solid);
}

---

And here is 2 frames of the output:

x: -512.035
y: 236.587
z: 136.929
distance to ground: 0.000
move to x: 2.971
move to y: 0.000
move to z: 0.000
distance moved: 0.000
in solid: 0.000

// .. next loop
x: -512.035
y: 236.587
z: 136.929
distance to ground: 0.000
move to x: 2.979
move to y: 0.000
move to z: 0.000
distance moved: 0.000

Notice that I'm attempting to move the entity forward 2.979 quants. c_move isn't moving the entity. However, it's also not reporting that I'm stuck in a block. During these frames, I'm not trying to move in the z-direction. distance_moved is set to 0.

I took my project and stripped it down to the bare essentials for testing. I was able to create a project where you can easily recreate the issue. You can download my example project here. In the demo, if you hit 'p', you'll be positioned to a trouble spot that's easy to get stuck on. Try hitting 'p', then a or d to strafe left or right. You should immediately find yourself stuck.

Here's my movement code:

Code:

---

action move_me()
{
	
	VECTOR move_to_vector;			// Holds the relative x,y,z values that are added to the character's position 	
	var distance_to_ground;
	var distance_moved;
				
	move_to_vector.x = 0;
	move_to_vector.y = 0;
	move_to_vector.z = 0;
		
	wait(1);
	c_setminmax(me);
	vec_set(my.min_x,vector(-8,-8,-20));
	vec_set(my.max_x,vector(8,8,20));

	while(1)
	{
			
		accelerate(move_to_vector.y, (key_d * strafe_speed * time_step * -1), 0.8); // strafe right
		accelerate(move_to_vector.y, (key_a * strafe_speed * time_step), 0.8); // strafe left
		accelerate(move_to_vector.x, (key_w * run_speed * time_step), 0.8); // go forward
		accelerate(move_to_vector.x, (key_s * run_speed * time_step * -1), 0.8); // go back
				
		distance_to_ground = c_trace(my.x, vector(my.x,my.y,my.z - 500), IGNORE_ME|IGNORE_PASSENTS|IGNORE_PASSABLE|IGNORE_SPRITES|USE_BOX); 	
		move_to_vector.z = -1 * distance_to_ground;

		distance_moved = c_move(me, move_to_vector, nullvector, GLIDE|IGNORE_SPRITES|IGNORE_PASSABLE);

		wait(1);		
	}
}

---

I've tried compiling my level with Don't snap verticies on and off. I've also tried Merge across leaves. Neither makes a difference.

Thanks!
- Bret

Thanks for the info - can you send that test project to the support? I'll look into this.

Thanks jcl,

Here's a link to the test level:

http://www.indiegamejobs.com/temp/mesh_bug.zip

If you'd prefer that I email it to support, I'd be happy to if you'd supply me with the email.

Thanks again!
- Bret

Thanks, I got it and will look into it next week.

Hi JCL,

Just a friendly reminder that I would love it if you could review this collision issue!

Thanks,
- Bret

I'll definitely look into it and will either provide a work around or a solution for the problem. It just didn't work this week so far and I'll be away the next 7 days, but I'll take care of it after my return - promise.

Fantastic! If I don't hear from you within about 10 days, I'll post another reminder. If there's anything that I can do to assist you in troubleshooting the problem, just ask!

Playing you demo in Lite-C, I cound only find one little part, where the entity got stuck.
(not really stuck, as it could move back), normally it moves fine.

Your problem is not really related to the BSP architecture/collision hull , but rather to a bad movement code.
You let your entity slide on te ground.
If you would walk in daily life like that - sliding with your feet tied to the ground -
you would trip over every edge in the carpet already.

You should write a better movement code:

First: lift a leg up. (move the entity up a certain amount)
then move the body forward (move into heading direction without movement in hight (z))
then take the leg down (move down the amount you moved up + the acceleration by gravity)

this way little edges on the ground cant make the entity get stuck anymore.

In the showcase I have a demo with an advanced movment code that is
not hard to transfer to Lite-C.

Hi Damocles,

Brilliant! At first I didn't think that your solution would be of any help, but the idea of keeping the bounding box above the level geometry solved the problem of getting stuck.

Here's a screen capture of where my new bounding box is positioned:



@jcl: My problem is solved! I'm still curious as to why the c_move didn't work, but I'm moving on. Feel free to ignore my bug submission if you don't have time to work on it.

you are welcome