possible for user attribute to drive the offset of image sequence

[Hos]

Hi,
Is it possible to have a user attribute of an object drive the offset of an image sequence on a texture?
This way I could have one shader on multiple objects and each object will have each own offset in the image sequence in the texture.
thanks,
Arjan

[Morbid Angel]

Yes I think this might work.

What you need to do is have a sequence like this tex.####.ext

On each object you must add a user string and put a number there. For example in my test 1001, 1002. In file node specify file name but replace tex.1001.jpg to tex.<attrName>.jpg (where attrName is your shape user attr name)Then for each of your textures you should get different maps loaded.

[Hos]

Hi Dmitry,
Thanks for your reply.
Is it possible to use this technique with an animated image sequence? So that every object has the animated sequence as a texture, but with a different offset in time.

[Morbid Angel]

I don't think so. The offset is not controlled by the renderer which is where the user attribute comes in. I'll ask a friend he might know.

[Hos]

That is too bad. It would be great if you could add a time variable to the string. Like image_<attrName + frame>.exr
Something like that wouldn't be possible right?

[Morbid Angel]

I don't think its impossible, but it would have to be done as expression not as render attribute.

[Hos]

Do you mean like a Post Translate Phyton Script or a maya expression?

[Hos]

Could there maybe another solution for this?
I have a large scene, where I want to have about 300 explosions occur a different times. To avoid having 300 shading networks I wanted to use the vray custom attribute to drive the offset in time of each explosion.
I found out that the custom attribute node doesn't work with the time offset of a image sequence.
I tried some different things like using a particle system with sprites for the explosions, but Vray doesn't seem to support the spriteNumPPP.
Then I made one image containing the whole image sequence in a grid (like a sprite sheet in games). I used the custom attribute in combination with the time node to build a network that looped through the grid. But I couldn't get it to work in the render.
The last thing I tried could be the best solution. I animated the uv of a Polyplane to match each frame of the image sequence in the the grid.
Then I exported that as a proxy, so I only have to set the start frame of each proxy for every explosion. This way I can use 1 shading network for all the explosions.
It would be ideal to have the custom attribute to drive the start frame of the proxy, so I could instance the proxy for each explosion and only use one proxy node and one shading network.
I tried to connect the output of a custom color node to the start of the proxy node, but it didn't work. Could there be another way to have instances of a proxy and have each instance his own start frame?

[vlado]

I think you can add a dynamic string or float attribute to the mesh(es), and animate that (maybe with an expression) to go through all the frames of a sequence, then use can use the name of the attribute as a tag in the file name. The dynamic attribute must have be named vrayUserScalar_tagName or vrayUserString_tagName - then you can use <tagName> in the bitmap file name.

Best regards,
Vlado

[Hos]

Thank you Vlado, that seems to be the best solution. I didn't expect that 300 simple expressions didn't slow the scene.