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Slugger
10-29-2007, 08:13 PM
yes, me again

is it possible to change a UV'ed characters mesh texture(bitamp) after render? I've seen replacement of "simpler" objects texture in tutorials, but is it possible to change say the diffuse bitmap for a charactermesh?

Cheers,

k.

PiXeL_MoNKeY
10-29-2007, 09:35 PM
Yes, but for best results you shouldn't render with the texture. There are various reasons for this:
1) The gbuffer channels used for that information aren't anti-aliased meaning jagged edges.
2) Shadows and lighting information is lost.

However, if you render the object using a solid white material and then use the replace texture operator set to Multiply. This means anywhere the original footage is white the new texture will be unchaged, where there are darker areas it will darken the new texture. This also, helps to get around the gbuffer aliasing issue.

For any of the texure replacement to work you will need RLA/RPF footage or use the gbuffer builder to build an operator containing the needed channels, check the Combustion help for information on what channels are needed.

-Eric

Slugger
10-30-2007, 11:17 AM
thanks again PiXeL_MoNKeY!

ok, yes perhaps better leave this plan of replacing textures to the renderer in the 3D app, are rendering with all things checked for the .rpf frames to have all options available(even though I dont' know half of what they actually do...), finding .rpf's good for many things but a let down in some areas, color corr of prerendered motion blurred frames are getting me not so good results, perhaps due to premultiply with alpha,


Cheers,


k.

PiXeL_MoNKeY
10-30-2007, 04:45 PM
You could look at render elements instead of RPF output. Here you could render the diffuse and other channels seperately so if a change needs to be made you would only need to render the information that is effected by the texture change (usually diffuse and reflection). What I posted does work and works well, but the RPF Texture Replacement is pretty slow. For color correction I use Straight/un-premultiplied channels and use 16-bit, 32-bit, or float colors.

You can divide, or un-premultiply, the alpha in Combustion by applying an Alpha Arithmetic Operator (Operator:Set, Operand:100%), do your adjustments to the colors, then apply a Set Matte (Layer:Original footage, Input:Alpha) or Compound Alpha Arithmetic (Operator:Set, Layer:Original footage, Input:Alpha).

-Eric

Slugger
10-30-2007, 05:26 PM
big thanks! PiXeL_MoNKeY

didn't know about divide or un-premultiply, will check it up, didn't have a clue one could do that even, I think I'll have to take a few days at a combustion class very soon...


Cheers!


k.

Slugger
11-01-2007, 02:07 PM
PiXeL_MoNKeY, did try your suggestion, could not make this work on my sequences, have .rpf's rendered premultiplied alpha, and all options checked,

tried to put the alpha arethmetic op on top of my footage, but not for color corr this time, now its a attempt to get rid of the premultiplied alpha's motionblur from 3dsmax, how can this be done, rerender w/o premultiplied?

*edit, PiXeL_MoNKeY, by doing this procedure you are describing is it applicable to rendered layers only(as in 3dsmax output to layers/combustion)?


Cheers,


k.

PiXeL_MoNKeY
11-01-2007, 04:34 PM
Make sure your RPF footage is set to Premultiplied to make it work. You can't divide/un-premultiply footage that isn't set to be premultiplied.

-Eric

Slugger
11-01-2007, 05:31 PM
I have checked store Alpha and premulti Alpha from withing 3dsmax, cant get it going in combust anyway, I just selected the footage and stick the operator onto it, perhaps this is not the right way to do it?

I guess it's clear to everyone now that I'm not very seasoned with combust, but what I try to do with a few of my sequences is getting rid of the smeared colour/background generated by the motion blur from 3dsmax(and I guess this phenomena is due to premultiply alpha), hope this makes sense


cheers,

k.

PiXeL_MoNKeY
11-01-2007, 07:15 PM
Did you read my last post? It says to make sure the footage (inside Combustion) is set to Premultiply. You have to set this on footage operator for the RPF footage.

-Eric

Slugger
11-01-2007, 10:01 PM
thanks Eric for your help, I feel like a total n00b, but I've set the .rpf footage to premultiply in the Footage Controls / Source / Color + Alpha / Premultiplied with [black]
cant find any other way to do it, I must be doing something bad, don't know what though, ahh, well, it's never to late to have a nervous breakdown


Cheers,

k.

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