[Sidefx-houdini-list] camera projection mapping

Jed Schwartz jed at jedschwartz.com
Mon Jul 14 18:17:09 EDT 2008

Thanks Andrew-!

We'll give it a shot-

On Jul 14, 2008, at 5:07 PM, Andrew D Lyons wrote:

> Hi Jed,
> You need to work with uv layering.
> Look at:
> group - prim grp by normal - backface from camera - if you only want
> to effects uv's on front faces.
> uv texture sop - choose project from camera. (the camera you will
> render the still for painting from)
> layer sop - has all kinds of controls for blending uv layers using  
> masks etc.
> attribute - to rename (store) incoming uv attrs and reinstate them on
> output. Why? The uv texture sop will always work with uv layer 0. ie
> "uv". You will often want to add a new layer (or blend with another
> incoming uv layer). ie uv1 uv2 uv3 uv4 attrs. If you have all this in
> a HDA, then the attr sop will let you rename uv to:
> uv`ch("../uv_layer_id")` etc tc.
> In your shader, use the matching uv layer for each texture. Blend
> colors etc as needed.
> Good luck!
> Cheers
> 2008/7/14 Jed Schwartz <jed at jedschwartz.com>:
>> I'm exploring  the possibility of using camera projection mapping
>> techniques (used quite successfully in a lightwave project) in our
>> current production that calls for a bunch of extreme close up detail
>> shots, mixed with broad sweeping moves across  very detailed martian
>> terrain.  We have all our terrain built and a great set of very hi-
>> res textures matching the DEMs we used to generate the terrain.
>> Most of our shots are blocked out and approved for final render, so
>> were to that stage where we're trying to figure out the most
>> practical way to get detail into our shots where we need it- We have
>> completed a few shots using Y projection maps with all the usual
>> tiling, depth maps et-al- Very labor intensive and lots of extra
>> detail generated that the camera will never see-
>> My colleague who did this in lightwave breaks down his procedure into
>> the following steps:
>> 1. Finalize the camera move
>> 2. Select "key" frames for terrain plate paintings
>>   For a locked-off shot or a very small pan, one "key" painting
>>   should be OK. For larger camera moves you may need to use several
>>   paintings to cover the entire terrain seen by the camera. Instead
>>   of using the (moving) final render camera I'll make a copy of it  
>> and
>>   delete the motion so that each "key" painting camera is separate
>>   and stationary.
>> 3. Render a "screenshot" from the view of the plate camera
>> 4. Paint on top of the screenshot
>> 5. Project the final texture back through the plate camera onto the
>>   terrain.
>> The main reason to use this paint-projection technique is to get  
>> around
>> the problem that ECU images never quite have enough resolution to
>> look "photorealistic" for my typical MER shots. The disadvantage is
>> the high amount of labor to set up each shot; the advantage is being
>> able to put high-resolution detail exactly where it is needed for any
>> given camera move.-
>> I'd be most grateful if anyone who has explored this approach to
>> projection mapping in Houdini and would be willing to share some
>> insight into this process-
>> Thanks!!
>> Jed-
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> -- 
> =======================================
> Andrew D Lyons | Digital Artist | http://www.tstex.com
> =======================================
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