Greetings, I've tested to use Thunderloom with Vray 3.6 for my recent project, and it worked very well and it was so impressive. This tool enable artists to create entirely new and believable fabric texture. But it doesn't seems to work well with Vray 4.x (aKa Vray Next), There were error log like, 'BRDFThunderloom shader cannot be loaded.'

• Diffuse amount slider (mult) Multiply diffuse color with this factor.

• ~~texture gamma text field~~ ~~"texture gamma" field where the user could input the gamma to be used for all the colors. Currently they each need to be linearlized individually which takes a lot of work to set up. So having a single place to control this for all the diffuse colors would be very helpful. The pseudo code would be "pow (color, texture_gamma)" so the default value of 1.0 would leave the colors unchanged, and a value of 2.2 would linearize all the diffuse colors from sRGB (2.2) to linear (1.0).~~

Suggested by Derek Flood.

The shader does not appear in the GI render element (RE) and it is also missing in the diffuse RE. It would be really great if it could appear in the diffuse RE because then one could bake the diffuse WIF pattern into a texture map. This would open up TONS of really great possibilities for look-dev, and so.would be my number 1 wish.

Suggested by Derek Flood.

The function tl_eval_texmap_mono_lookup in vray_thunderloom.cpp is not implemeted. This means that there will be problems when varying yarnsizes non-uniformly, such as with a changing texture. I can't find a way to achieve this sort of lookup using the V-Ray APIs.

See my question on the ChaosGroup forums for more info: https://forums.chaosgroup.com/forum/v-ray-for-maya-forums/v-ray-for-maya-sdk/76255-texture-lookup-with-uv-on-non-bitmap-textures

See the implementation of tl_eval_texmap_mono_lookup in vray3dsMax/3dsMax/Eval.cpp for how it works in V-Ray for 3dsMax.

Modified pr #36 to use a separate parameter for opacity - instead of alpha channel Only tested in 3ds Max for now.

Here's a material with yarn size 0.3 (and transparency between the yarns):

Maya will crash if there are too many "daisy chain" connections into Thunderloom shader.

For example if I connect a file texture to the type1 spec color, this works fine (a into B). Further, if I connect a file texture to a VrayFalloff, then connect that to the type1 spec color (a into b into c) this also works fine. However if I add an additional step to the daisy chain: texture map > gamma > falloff > thunderloom spec (a into b into c into d), this will crash Maya. In other words if the daisy chain gets too long (three links) it crashes.

Work around is of course to minimize the node chain length.

I've been testing the "alpha" slider that Peter revealed for me in a branch of the shader, and can say that it is really helpful for getting "metallic" fabrics like silk to look right (honestly I was not able to get silk to look right without it). So I'd put in my vote for keeping this exposed in the shader. For example, changing the alpha from the default value of 0.05 to 1 makes the spec basically uniform like a metal, rather than a dielectric material. Thus giving the "metallic" look of a silk.

I would suggest giving it a more descriptive name than "alpha" which indicates its purpose, like the other attribute names in the shader do. Perhaps you could call it "uniform specularity" or maybe even "metalness."

tlColor struct now has alpha channel. But it is only used in the diffuse evaluation. Plugins use alpha channel to tell vray about transparency.

Following still needs to be done...

• [ ] Expose alpha in 3dsmax UI for diffuse colors.
• [ ] Bump PTN file version. Make conversion pin file conversion function that adds alpha 1.0 to old colors.

hey! im new in 3dmax 2015- vray 3.0, i want to use "ThunderLoom" is it possible? I already read several post here about installation, was like Chinese :D.. i really dont know Cmake, SDK, .... how to do it

Feature request: It would be helpful to have a checkbox option under "reset yarn types from file" to "keep default yarn type settings." That way if one wanted to change the pattern (PTN/WIF) they would not lose the default yarn type settings when they loaded it in.

Bug: Having zero in the bend will break the shader, meaning the spec goes black. Non-zero values (0.001) work fine. So perhaps the slider should be made so it cannot go to zero, but just a little above that.

E.g.

BRDFThunderLoom BRDFThunderLoom { filepath="test2.ptn"; uscale=4; vscale=4; uvrotation=0; yarnsize=List(0.1, 0.2, 0.3); yarnsize_on=List(1,0,1); }

Won't load yarnsize and yarnsize_enabled values for yarn type 0, 1 and 2. yarnsize_enabled is always 0 and yarnsize will be set to the last value, for all yarn types.

The current diffuse shading is quite lacking. To improve this, we should probably look at how it’s done in hair shaders. I believe what we’re after is multiple scattering. The specular reflection is single scattering since the light scatters once before leaving the yarn. I have found this paper: http://www.cemyuksel.com/research/dualscattering/dualscattering.pdf which seems like a good starting point. It is referenced from Pixar’s memo on hair rendering found here: http://graphics.pixar.com/library/DataDrivenHairScattering/paper.pdf I believe @sharktacos has a lot of insight into how this is handled in hair shading

The 3ds max and Maya versions of Thunderloom could perhaps be added to the Autodesk App store for easier installation. There are instructions here: https://help.autodesk.com/view/3DSMAX/2019/ENU/?guid=__developer_writing_plug_ins_packaging_plugins_packaging_plugins_html Perhaps this should wait until v 1.0 is done?

It would be nice if the shader worked with bump and normal maps. This is particularly useful in simulating subtle wrinkles in fabric, as seen in this example (currently done with displacement)