How to use COPs with a specific frame for material overrides?

[magneto]

Hi,

I am trying to use a COP as a material override. For the material itself, if I just type:

op:/img/img1/mycop[/CODE]

It works fine. But For the material override, I had to use:

[CODE]`op:/img/img1/mycop`[/CODE]

Is this normal? I thought bought parameters were string.

Also I noticed when I first used the material override but left the actual parameter empty, Render View still didn't pick up the COP as a texture. Only after I pasted the same path without backticks into the actual material, it rendered correctly.

Not sure if I am doing it wrong or if the renderer have to be forced to update for these?

My actual question is, how can I specify a specific frame from that COP? It's not a sequence but it's animated so I want to specify a different frame for each point.

I tried:

[CODE]`op:/img/img1/mycop[$F]`[/CODE]

but it didn't work.

[size=4]Thanks [/size]

Edited July 16, 2013 by magneto

[malexander]

You have the op: syntax right, it's op:/path/to/cop[frame#]. But I suspect you want [$PT] or [$PR] to specify the cop frame, rather than [$F].

[magneto]

Thanks Mark, I tried $F, or a number but Mantra printed to the console that it couldn't find it. Is it because my Font COP is not an actual sequence? I was basically trying to get the result of it on a specific frame which by default would be the frame number you are on, since it's using $I.

[magneto]

I attached my file to show the problem.

Right now I am just trying to show the COPs as textures but Mantra doesn't see them. It just prints:

mantra: Unable to load texture 'op:/img/img1/font1'[/CODE]

But in the viewport, they show up fine. So I think this might be a bug.

Thanks guys.

coprender.hip

Edited July 17, 2013 by magneto

[graham]

The issue is that Mantra doesn't understand the OP syntax. Mantra has no concept of what an operator or what a Font COP is. This is the same sort of thing if you were to say point a shader to a point cloud file that was really an op: reference: No clue what an operator is.

When you assign it as a regular material I'm guessing Houdini will pass the resulting image of your operator to the IFD so that Mantra has something to render. However, when it is defined as an override there is no way for Houdini to know that it needs that information in the render.

[magneto]

Thanks Graham I didn't know that. I wish the shader would automatically translate the op path to an image. Because the viewport material shows up fine.