Several questions, regarding VMantra

[MG]

Recently I've been rendering and compositing quite a bit. I was wondering:

• Is it possible to render seperate specularity, reflection, bump/displacement passes? If so, how?
  
• In Windows, how can I see the verbose output? Starting Houdini from a shell, even a Cygwin (bash, tcsh, csh ..) shell, doesn't make much difference. Is there a way though? (aside getting it via hscript).
  
• Where did the, atmospheric, "Halo" shader go? I saw it in an old SESI Legacy tutorial, this one to be precise, but can't find it in Houdini 6.x+.
  

Thanks in advance!

[TheDunadan]

Concerning the renderer passes:

Rendering seperates passes is pretty much straight forward. If you go into the deep raster tab of mantra, there are already quite a few predefined 'pass variables'. However if you want extra passes, you only need to declare those in the shader and create an extra pass for those, e.g. if you have some component for specular

C_Spec = ....

just add C_Spec in the deep raster tab and once this value is generated by the shader, it's value will be rendered into the specified seperate layer. (at least it something very close to that ... some weeks ago I last did that).

Jens

[MG]

just add C_Spec in the deep raster tab and once this value is generated by the shader, it's value will be rendered into the specified seperate layer.

14860[/snapback]

What kind of shader value do you mean? Global shading parameters or?

I don't really get it, I've tried a few things but it didn't really work.

[sibarrick]

What kind of shader value do you mean? Global shading parameters or?

I don't really get it, I've tried a few things but it didn't really work.

15112[/snapback]

Inside your shader code - or easier if you are new to this in a VOP network create a parameter vop and turn on export parameter then wire whatever value you want in your deep raster into the input of this parameter vop. In the deep raster tab of your render add the name you gave your parameter, (where is says Parameter Name on your parameter VOP, not the label)

Hope this helps a little.

[sibarrick]

As to verbose output. Click on the little plus sign next to where it says

Render command "mantra". This brings up more render options, on the output tab turn on verbose and then specify an output file.

Sorry can't answer the Halo question

[TheDunadan]

If you want to do it the vex way, check Jason's tutorial on shader writing. He wrote something like this:

surface plastic(vector amb=1; vector diff=1; vector spec=1; float rough=0.1)
{
  vector nml;
  nml = frontface(normalize(N), I);

  Cf = amb * ambient(); // add ambient (tinted by user parameter)
  Cf += diff * diffuse(nml); // add diffuse (also tinted)
  Cf += spec * specular(nml, -normalize(I), 1.0/rough); // add specular (also tinted) 
}

Cf is the final color value that mantra renders and unfortunally although it is made up of an ambient, diffuse and specular part, all that seperate information gets lost.

surface plastic(vector amb=1; vector diff=1; vector spec=1; float rough=0.1)
{
  vector nml;
  nml = frontface(normalize(N), I);

  c_amb = amb * ambient(); // add ambient (tinted by user parameter)
  c_diff = diff * diffuse(nml); // add diffuse (also tinted)
  c_spec = spec * specular(nml, -normalize(I), 1.0/rough); // add specular
  Cf = c_amb + c_diff + c_spec;
}

Obisouly this second VEX code does the same, however we didn't write it all into Cf directly, but stored each in a seperate variable. Now you can add in the output options as sibarrick desribed c_spec and the final image would contrain an extra c_spec pass now, that stores only the specular information.

So the good thing is, you have really totally total control , but you need to adjust the shaders first on VOP's / VEX level and it takes slightly longer to render as well (though much less then rendering it all sperately).

Jens

[Lukich]

To get to the Halo and Glow atmospherics, go to VOPs > Fog Shader. Both halo and glow are inside of it.

[edward]

Don't you also need to export the c_spec, c_amv, c_diff parameters?

[deecue]

there was a video tut out there on rendering passes.. did a quick google search for it with no luck. i have a back up of it, but it's 24 megs and dont think odforce would allow that..

its filename is ccount.php.avi (or prob more so ccount.avi out on the web) so maybe someone else would be able to find it..

if no luck and odforce cant host it somehow, maybe i can throw it up on a webserver or something..