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Baking Indirect Illumination

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The title says it all - it seems like it should be a very simple thing (or widely used at least) and yet after two evenings of trying and failing and googeling I'm nowhere closer to a solution.

I want to bake the indirect illumination of a scene into a texture - which later I want to add to the diffuse channel to save some rendering time and cut the diffuse bounces. The Houdini help mentions baking indirect illumination, but in the "bake Texture" node there are no options on number of bounces like I have in a normal Mantra. I never see the effects in the generated map - there's only the direct lights - and when I extract just the indirect channel it's always pitch black.

I tried using a gilight - but that also doesn't seem to work. I can use it fine rendering with a normal mantra (there I see it's effects with using a prerendered photon map that I load) but it has no effect on the baked texture.


Any help pointing me in the right direction would be greatly appreciated.
Cheers, Marco

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well baking lighting is actually very easy but not that straightforward as some essential parameters are not exposed in texturebake ROP (for who the hell knows the reason).

i think the issue are two things in your case:

1) there is option to Disable Lighting/Emission in Baking tab on texturebake ROP which is on by default. that obviously needs to be off to be able to get any lighting information. After that you should see direct lighting in your main channel.

2) for indirect pass you have to actually add Limits tab to be able to control indirect rays contribution and bounces (thats the one which is not exposed). You can do that by going to Edit Rendering Parameters (little gear icon in top right corner of the parameters window) and filtering your search to "limits". then just add the whole tab by drag n dropping or by arrow icon. then there should appear a new tab Limits on your ROP where you can specify bounces (default is 0, that's why it was black).

then you obviously gonna want to separate indirect light pass and you can do that in Images>Main tab where you can add Extra Image Panes and specify indirect lighting pass from drop down list.

check the file attached if you still feeling lost :)

cheers, D.



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Wohoo - Sir, you deserve a Cookie (if your browser accepts them : P )!

Solved! Many thanks!

Edited by marcosimonvfx

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Hi, I'm having a similar issue. So I am trying to bake hair curves/ groom on hair cards with the texturebake ROP. So I couldn't get the Indirect lighting as well before, but reading this tread, I managed to get the proper image plane.


The main issue I am having is that I need to get the reflection/ refraction image planes as well. I think this has to do with the fact that there is no point camera to create incidence angle with the hair curves so that specular highlights/ reflections would be created and baked onto the card. 

So I tried to have the position of some arbitrary camera be referenced in the hair shader and plugged into a refract and reflect lighting node that then gets bound out to a custom attribute, which is referenced in the extra image plane.

Still renders black. Please, If anyone has an idea how to solve this, I'd be most grateful :))


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