Cell Shader

[Isleofgough 4]

I have looked at various ways of rendering just the visible edges in Houdini, and it seems like I have to use Flipbook. To add the lines on top of an existing texture, I have to do a double render and composite them. Is there a shader that basically just adds lines (multiplying an image of the edges on top of a constant or principled shader?

[davpe 183]

unfortunately no, there is no dedicated wireframe shader in Mantra. but there is a pretty easy geometry based workaround that gives decent results. check the file in attachment, hope that helps.

cheers, D.

 

wireframe.hiplc

[Isleofgough 4]

That is a clever solution. Thanks!

[Isleofgough 4]

I still think there must be a way of doing this all in a shader. (since many other 3D programs DO have a built in cell shader). I know absolutely nothing about what I'm doing in shader editing, but I tried to at least get a start with this. If I could remap the greyscale with some sort of ramp to pure white and pure black, I would be very close. I'm guessing this wouldn't work if actual UVs were applied:

 

FakeCellShader.hiplc

Edited June 15, 2018 by Isleofgough

[toadstorm 298]

you're almost there, just need to compute abs(0.5 - s) and see if it's less than your chosen edge threshold value. granted, this still is going to render the edge width as a percentage of the parametric UVs instead of a constant world space width, which is why i like the Convert Line method better.

FakeCellShader_ts.hipnc

[Isleofgough 4]

... almost as in ~20%, but thank you. I see what you mean about the Convert Line method too.

[thx1138 8]

You could measure world distance from P to edge (primuv(0, "P", primnum, {0,1,0}) and remap the result to 0-1. In that way edge width maintain in world space units. Here is example file.

wireframe_shader.hip