Do Decals work correctly after a dForce simulation ?

ibr_remote aka infinity10

I don't have much experience using decal nodes, and I notice that after a dForce simulation drape has been done, the decal isn't always as I wanted it positioned.  

crosswind

Yes... after simulation / posing etc. in some cases, you have to reposition the decal node so as to get the correct projection of the texture maps.

NorthOf45

There is a way to maintain relative position, even with posing and draping. By default, the decals project straight onto the surface, like a, um, projector, because of the projection mode used.

To make it always fit the surface regardless of posing or draping from simulation, change two settings on the decal from the default settings:

Decal->Projection->Coordinates->Texture Coordinate System : UVW
Decal->Clipping->Clip Mode : UVW

The decal will now fill the entire square area of the target surface UV map, regardless of where the actual surface lies within it. The image will follow any deformations in the surface without shifting around, so no repositioning needed. Works best with a surface UV map that is centered in the square, but the position can be adjusted with the Projection transforms [X, Y, Z] Projection [Rotate, Scale, Translate] (NOT the decal General transforms)

I learned this from a product that used this method. I was skeptical of how a decal could be used as a texture map for a dForce cloak, seeing as how it would obviously move around, but it works well, once you know the trick. Too bad these decal parameters are not well-explained (not that I have found).

ETA: With clipping mode "Position and UVW", you can position the Decal with its General Transforms.

crosswind

That'll be case by case... Setting UVW in Texture Coord. System may bring unexpected result on lots of clothing... even if one can tweak Projection transforms...

Some issue may happen to Clipping as well... depending on the dForce settings and its result as per one's need. For instance,  a typical example : I usually shorten skirts by setting small contraction value on dynamic surfaces. If there're decal nodes working well on the original skirt, after shortening it, I have to reposition the nodes as well as rescale them as needed... they don't follow the move of vertex positions ~

NorthOf45

I beg to differ. Setting both parameters to UVW avoids that problem. By definition, the decal will follow the uv mapping. I am no expert, but I can see that it works as I expect.

crosswind

I experimented a lot with different coord. options, nope, it always gave me unexpected result especially distortion... So that's why I never use that option but just tweak a bit as needed... it's not a big deal for me anyway.

NorthOf45

Okay. If the mesh is changing size, the decal will also change size, which is following the uv coordinates. This would be undesirable if you want the size and/or shape of the decal to remain constant. For posing and draping, the surface will warp and fold, and might stretch a bit, like in real life, but a decal would follow these movements. I suppose there is no perfect solution.

Richard Haseltine

It may also fail if the UVs are unhelpful for a flat image.

ibr_remote aka infinity10

Thank you everyone for all the interesting input.  It seems that a manual tweak post-simulation may be required in some cases.  A well-uv'd geometry helps, I gather.