Jump to content
chazfest

Water collision issue in matchmove project

Recommended Posts

Hi,

I'm continuing to trouble shoot my way through my first attempt at a matchmove project from Boujou to Houdini. The scene involves a short clip of a set of stairs in my house, down which I wish to throw some water. Sounds simple enough in my head, though I'm running into probelm after problem at the min.

So far, I've build my stairs up in Houdini, using the cam from the Boujou track. The track wasn't perfect in the first place, but will do for now so I can get my head around the principles of this workflow.

My problem arises when I try to introduce the water into the scene. It reacts initially with the null points (I think that's what they're called?) from the camera track, ie. the reference crosses in 3D space. No big issue, I turn their visibility off, yet the water now seems to interact with the step in a different position of 3D space. Basically, it's not hitting the step, it's somehow hitting an invisible point above the step, probably twice it's height in the air.

Wasn't sure if this would ring any bells on such a project? Or if anyone would be good enough to take a look at the project file for me? I'll upload if so :)

Thanks in advance.

Chaz

Share this post


Link to post
Share on other sites

Hi,

I'm continuing to trouble shoot my way through my first attempt at a matchmove project from Boujou to Houdini. The scene involves a short clip of a set of stairs in my house, down which I wish to throw some water. Sounds simple enough in my head, though I'm running into probelm after problem at the min.

So far, I've build my stairs up in Houdini, using the cam from the Boujou track. The track wasn't perfect in the first place, but will do for now so I can get my head around the principles of this workflow.

My problem arises when I try to introduce the water into the scene. It reacts initially with the null points (I think that's what they're called?) from the camera track, ie. the reference crosses in 3D space. No big issue, I turn their visibility off, yet the water now seems to interact with the step in a different position of 3D space. Basically, it's not hitting the step, it's somehow hitting an invisible point above the step, probably twice it's height in the air.

Wasn't sure if this would ring any bells on such a project? Or if anyone would be good enough to take a look at the project file for me? I'll upload if so :)

Thanks in advance.

Chaz

Hi Chaz,

Well it's hard to tell without seeing the shot, it could be a range of things. But I would start looking at the collision geometry of the stairs. You can find it on the 'stairs' static object in DOP's, you can turn off 'Display Geometry' and all the way at the bottom, at the collisions tab turn on 'Show Collision Guide Geometry'. This should show you a red representation of the stair in a way DOP's sees it. If it doesn't match you stairs you can crank up the resolution of the collision geometry.

It also depends how you display the fluid, because if you look at it in particle mode (Assuming you're using FLIP) than yes there will be a gap, but thats due to the particle size which should be come clear if you switch to sphere or sprites (on the fluid object). Apart from that it's hard to say without a scene file.

What I don't get in your explanation is that you say that the fluid collides with the null objects you imported from boujou? I'm really curious how you accomplished that, because as far as I know that's not easy, like clicking on a shelf button.

Hope this helps,

Nick

Share this post


Link to post
Share on other sites

Hi Chaz,

Well it's hard to tell without seeing the shot, it could be a range of things. But I would start looking at the collision geometry of the stairs. You can find it on the 'stairs' static object in DOP's, you can turn off 'Display Geometry' and all the way at the bottom, at the collisions tab turn on 'Show Collision Guide Geometry'. This should show you a red representation of the stair in a way DOP's sees it. If it doesn't match you stairs you can crank up the resolution of the collision geometry.

It also depends how you display the fluid, because if you look at it in particle mode (Assuming you're using FLIP) than yes there will be a gap, but thats due to the particle size which should be come clear if you switch to sphere or sprites (on the fluid object). Apart from that it's hard to say without a scene file.

What I don't get in your explanation is that you say that the fluid collides with the null objects you imported from boujou? I'm really curious how you accomplished that, because as far as I know that's not easy, like clicking on a shelf button.

Hope this helps,

Nick

Hi Nerox, thanks for the help. I'm still getting nowhere fast by the looks of things! lol. The collision geometry seems to line up perfectly with the top step.

Still, the water seems to somehow collide with the crosses / reference points.

I've uploaded the project file, in case you'd be good enough to check it out. No worries if not. I just have no idea what I've done wrong here. lol. Possibly a concoction of things!

Thanks again.

Chaz

Stairs Track NEWEST Houdini Comp.hipnc

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×