this might be a stupid question ...

[dangerweenie]

But does anyone know of a good workflow to take a dynamically fractured cached simuation from houdini, bring it into maya as a .bgeo or .obj sequence, and have all the UVs work such that the texture sticks to the breaking pieces?

I would imagine that this involves calculating the UVs based on the very last frame of the sim, and then getting all the sub-fractured pieces snap to the boundary of UVs of their parent pieces. The attached screenshot does not seem to be working as I imagined.

I only need the outside of the surface to be textured.

Any help is appreciated!

Best,

Matt

[lukeiamyourfather]

Using UV maps with changing topology (like fractured objects) is a no go. Use the rest position of the pieces and create a procedural shader that relies on the rest position to lookup noise and/or patterns.

[dangerweenie]

Hi Luke,

Thanks for the reply.

It sounds like what you are suggesting is similar to the "set texture reference object" function within Maya.

I have to texture / shade, light, and render in Maya, so I'd need to get UVs out of the cached sequence.

It seems like redpaw was able to pull something like this off here, no?:

I'm still a little bit in the dark about how to use the vertex point attr to get the UVs to stick, even on the dynamic fracture geo.

Best,

Matt

Using UV maps with changing topology (like fractured objects) is a no go. Use the rest position of the pieces and create a procedural shader that relies on the rest position to lookup noise and/or patterns.

[Alexander Weide]

Dont be afraid of asking. There are no stupid questions on earth!You use Houdini - a stupid person cannot find the button to open this peace of software.

[lukeiamyourfather]

Hi Luke,

Thanks for the reply.

It sounds like what you are suggesting is similar to the "set texture reference object" function within Maya.

I have to texture / shade, light, and render in Maya, so I'd need to get UVs out of the cached sequence.

It seems like redpaw was able to pull something like this off here, no?:

I'm still a little bit in the dark about how to use the vertex point attr to get the UVs to stick, even on the dynamic fracture geo.

Best,

Matt

Forget about UV maps and textures, they are not an option. As the object fractures Houdini will automatically create the rest position of each point on the mesh. So as the object breaks up more and more all of the pieces will still have rest positions relative to where the piece fits into the original object before fracturing. Use that rest position to look up procedural noise in three dimensions. I'm not sure how to do this in Maya, or if you can even do it at all in mental ray, but that's the idea. Again, forget about UV maps and textures because they simply won't work in this situation.

[dangerweenie]

Hi Luke,

Thanks for the reply.

So I get what you're saying, and the the risk of sounding daft, it looks like redpaw was able to get consistent UVs on geo that was dynamically fractured . He is using a file texture (houdini's "uvcolor.gf"), not a procedural world-space shader (noise, ramp, cloud, etc).

UVs are included in an OBJ or .bgeo export. They're embedded in each frame of the sequence.

Did you take a look at that file / post I linked to in the last reply? I must be misunderstanding a part of the process, because running the sim and keeping the UV texture window open, I can see that they do not move around from frame to frame, despite changing geo and vertex count. This is enough for me to apply a file texture in Maya + V-Ray, Mental Ray, etc.

Velocity would most definitely be a no-go, however.

Thanks again for the reply, would like to hear what you think of that example, in the event that I am still barking up the wrong tree.

Best,

Matt

Forget about UV maps and textures, they are not an option. As the object fractures Houdini will automatically create the rest position of each point on the mesh. So as the object breaks up more and more all of the pieces will still have rest positions relative to where the piece fits into the original object before fracturing. Use that rest position to look up procedural noise in three dimensions. I'm not sure how to do this in Maya, or if you can even do it at all in mental ray, but that's the idea. Again, forget about UV maps and textures because they simply won't work in this situation.

[lukeiamyourfather]

Hi Luke,

Thanks for the reply.

So I get what you're saying, and the the risk of sounding daft, it looks like redpaw was able to get consistent UVs on geo that was dynamically fractured . He is using a file texture (houdini's "uvcolor.gf"), not a procedural world-space shader (noise, ramp, cloud, etc).

UVs are included in an OBJ or .bgeo export. They're embedded in each frame of the sequence.

Did you take a look at that file / post I linked to in the last reply? I must be misunderstanding a part of the process, because running the sim and keeping the UV texture window open, I can see that they do not move around from frame to frame, despite changing geo and vertex count. This is enough for me to apply a file texture in Maya + V-Ray, Mental Ray, etc.

Velocity would most definitely be a no-go, however.

Thanks again for the reply, would like to hear what you think of that example, in the event that I am still barking up the wrong tree.

Best,

Matt

Creating consistent UV maps is possible but even if you get them the workflow for texturing it will be cumbersome (making sure edges line up, sorting which piece is which, etc.). The best way to create shaders for this kind of object is procedurally and relying on rest positions. I suppose if the object is a hero asset then it might be worth the trouble. The call is your's but I certainly would do it procedurally.