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Hi,
I am play with the physics2D of AppGameKit lately.
I try to learn how the joints works. I created a prismatic joint If I prevent the rotation of one sprite of the joint, using the command

then the command

has no effect.
Is it possible to create a prismatic joint but restrict the rotation of the whole body?

EDIT: I uploaded the project

george++,


+

= the angle between the 2 sprites should always = atanfull(x2# - x1#, y2# - y1#). you can't get any more restrictive than that


otherwise, i think you're misunderstanding the parameters of the prismatic joint:

IE, i don't understand your use of GetSpriteXByOffset(spr2), GetSpriteYByOffset(spr2) for vx, vy where those params represent which axes (relative to the angle between the 2 sprites) that the sprites can move along (x &/or y).

so, 0 or 1 for each parameter/axis (<< it might not be as simple as that. i haven't explored other values). add again: (it's the vector. i get it now...)

you're doing similar with the x, y params using GetSpriteXByOffset(spr1), GetSpriteYByOffset(spr1) as the joint's anchor point (vs, perhaps, the center-point between the 2 sprites that i might have expected?) .

i just realized, you want spr2 to rotate around spr1? (where you have set x, y properly, if that's the case)

so, questions:

do you want the joint to be centered between the 2 sprites?

do you want them to stay within a certain range of eachother?

do you want the joint/center-point to be able to rotate (and be limited?) ?

do you want the sprites to be able to rotate independently from each other (and be limited) ?

the short version: can you better describe your desired effect?

btw, i've taken some time off from work recently and have spent some of that digging into all things box2d.

from that:

Prismatic Joint


the small % of what i've retained thus far has shed some light on AGK's implementation of box2d (including the fact that AppGameKit has implemented a seemingly-random scale of 0.2).

as i'm still sorting things out in my head, i've been shying away from such things as this recent Q re: Range of Forces where the answer isn't so simple.

= neither, directly.

meanwhile, i've updated the previous response re: vx, vy... sorry to have this stuff spill/trickle out ass happen

i need to "step away"... maybe even go back to work! heh

Thank you for these detailed indormation. It is true that I didn't understand exactly the parametres of the creation of the joint.

Yes, but without any rotation. What I need is to create a platform. The platform consisting of two or more pieces. I need to create a joint between these pieces ,but set the velocity only to one of them.
So far I was able to create the platform using kinematik objects and controling their velocity one by one. I thought that it would be more efficient, if I create a joint and move only one object of them.

i think i get it.

try keeping the primary piece as kinematic and make any other sprites/pieces that you want to attach to the primary as dynamic and attach them with a weld joint.

by the way, your background graphics are gorgeous. even more so if those lanterns swayed with the breeze

Thank you for the tip. I'll try it

Indeed. I downloaded it from craftpix.net. It is in .ai format also. A digital artist could animate the lanterns with ease...