first i need to say irradiance caching is a great feature. it makes GI usable without needing dual xeons

here's a couple more questions if people dont mind..

im sure it doesnt - but does the position of the GI light in my scene matter, or is it just there to enable the solution? only one needed per scene? as i increase the samples, my shadows disappear… not totally but they are too light..

the solution was to include a shadow shader on the non-GI lights… this works well, although it isnt the perfect realistic shadows that the GI makes… its good enough but im wondering if this is what you pros would do or is there a trick for the GI shadows?

finally, ive followed the training videos but im still having a problem with UV mapping.

i make a tube, UV Project set to cylinder and made to fit, then assigned a shader. i would expect the texture to be wrapped around the tube, the problem is that it is assigned to each face of the tube, not the tube as a single object.

the shader has a UV Project VOP with U and V plugged into S and T on the texture. but no matter what i do with the texture gives the same results.

Edit: it frustrated me all weekend - i just now thought there might be a global/local setting like a polyextrude… i will check tonight and update the post… if thats the answer pls disregard this question!

thanks for reading, in the past months ive asked questions that cover a huge range of material, maybe im trying to learn too much at once.. I just want people to know its all been a huge help, and in time I will fully appreciate those answers that go beyond my current skill level. In other words im not just asking a million questions and then not using that info, thereby wasting people's time… its all noted 8)

im sure it doesnt - but does the position of the GI light in my scene matter, or is it just there to enable the solution? only one needed per scene?

Yes, only one per scene, and no, the position is irrelevant.

as i increase the samples, my shadows disappear… not totally but they are too light..

the solution was to include a shadow shader on the non-GI lights… this works well, although it isnt the perfect realistic shadows that the GI makes…

There's nothing wrong with having more shadow solutions in your shot. Think of the GI light as an occlusion layer - it can provide you with some very nice(and expensive ) indications of light and dark in your scene. You may want to consider rendering just an occlusion layer that is grayscale and can be used in a composite to lighten and darken the scene. Here you can also increase the contrast and this can let you darken your shadows. This grayscale layer may not always work, however, depending on the sorts of things you're rendering and the subtlties involved, but typically I'll try to render a shadow pass separately anyway for inclusion(and control) within the composite. This can include many different shadow solutions.

Yes - the ol' uv projection onto the poly object quiz…

This is annoying - essentially what's happening is that each poly is getting the s&t mapping params and you're getting this duplication of the texture on each one. Here's how to get around this: you want to grab the uv's that are actually assigned by the UVTexture SOP without this remapping happening. To do this, in your VOP shader put down a Shading Layer VOP and ensure UV is selected. Connect this to a Vector To Float VOP, and feed the first output of this into the S input of your texture VOP(or whatever you're doing that wants ST), and feed the second to T. The third is unused.

This should feed the proper coordinates to match what you're no doubt seeing in the viewport. I think there's another way around this, and also a good reason why this utterly non-intuitive behaviour happens(although I'm not sure about that), but I'm away from Houdini and drawing a blank(must be holiday syndrome ).

Cheers,

J.C.

i'm pretty happy to now see 1 monkey instead of 30 projected on to my surface

like you said not intuitive, i wouldnt have worked that out this century. but after clicking the ? it makes some sense, this VOP is used for different layered UV sets for layered shaders.. sounds good i'll try that another day

about the shadows it sounds like a seperate pass is the way to go, maybe even the GI which id never thought of but makes sense. compositing is something i neglected in my pre-houdini days. ill have a go at your suggestions for the shadows and get into some compositing.

thanks!

Mark

John's right that you only really need one GI light per scene, but I've found occasion to use a couple of them only because the VEX Global Illumination light shader doesn't give you a color Tint control per “type”. For purely “creative” reasons, I've used one for the Full Irradiance, and a seperate one for caustic photons, just because there isn't a control for each. That being said, its elementary to add it to the VEX Global Illumination shader yourself by making a quick copy of the shader to your own OTL and then adding the necessary VEX code to do it. (If you feel curious and want to do it and need some pointers, just shout.)

Cheers,
Jason

Hi Jason, I was just thinking last night that 2 solutions might be needed if using caustics in a GI scene! you saved me a question, cheers sounds pretty complex, ill give it a go when im on top of all this… getting there!

Keep in mind that you don't need two GI lights in the scene because the VEX Global Illumination shader will sum up all indirect light - e.g. from Full Irradiance and from caustics. The only problem comes in if you want to influence their color and intensity seperately, but the shader only has one global Tint color slider.

Some useful enhancments to that shader is to allow a tint per type and also a Saturation intensity slider per type too. With this you could manipulate the results quite nicely to get the look you want, instead just settling for the “correct” result. I'd say it's probably good practise to get the most accurate simulated result possible with all the tints/etc at 1 and then start to push it around creatively.

Take care,
Jason

ahh i get you… if you wanted a dull scene but intense caustics for example..

i can see how that would be useful.



cheers
Mark