VRAY NEXT_VrayBlendMTL + Vertex Paint Bug

[charlyxxx]

Hello, dear ChaosGroup Team. I found a bug with vertex paint layers and VrayBlendMTL.

So.

1. I've created 3 VrayMtl's and 1 VrayBlendMTL.
2. I've painted Vertex Channels with different VertexPaint modifiers.
3. I've tried to Blend this 3 materials with 1 VrayBlendMtl and VertexColor maps.

And one of the materials doesn't see VertexColorMap... and in result - we see only blend for 2 materials with one VertexColorMap..

This is a bug or I doing something wrong?

Here is the scene with this bug - https://bit.ly/2H2whQv

Best regards, Andrew.

[matanov]

This is a bug or I doing something wrong?

Hey Andrew,

If you want to achieve the effect from the Standard Blend setup, then you should follow the same logic for the VRayBlendMtl. In your current VRayBlendMtl setup you are masking on top of the previous coat.

So here is the proper one -

[charlyxxx]

Hey Andrew,

If you want to achieve the effect from the Standard Blend setup, then you should follow the same logic for the VRayBlendMtl. In your current VRayBlendMtl setup you are masking on top of the previous coat.

So here is the proper one -

Hm, yes in this way - it works =) Thank you =)

But this is very weird.

Because If I will use the standard image mask - any coat and blend layer - works fine. And as I understand it should works with VertexColor too... So this is bug =) Do you agree with me? =)

[vlado]

No, it's not a bug. It's a matter of maths (I know artists hate it, but it can be a useful thing). The two setups are simply different. In the standard blend material, your set up is described as

inverse(map#1)*(Blue material)+(map#1)*[inverse(map#2)*(Orange material)+(map#2)*(Green material)] which is equivalent to inverse(map#1)*(Blue material)+(map#1)*inverse(map#2)*(Orange material)+(map#1)*(map#2)*(Green material)

whereas your setup with one V-Ray blend material does the following:

(map#2)*(Green material)+inverse(map#2)*[(map#1)*(Orange material)+inverse(map#1)*(Blue material)] which is equivalent to inverse(map#2)*inverse(map#1)*(Blue material)+inverse(map#2)*(map#1)*(Orange material)+(map#2)*(Green material)

and as you can see the three materials have different weights in that case. It might be possible to shuffle things around so that you can still get the same result with one V-Ray blend material.

I hope this helps.

Best regards,
Vlado

[charlyxxx]

No, it's not a bug. It's a matter of maths (I know artists hate it, but it can be a useful thing). The two setups are simply different. In the standard blend material, your set up is described as

inverse(map#1)*(Blue material)+(map#1)*[inverse(map#2)*(Orange material)+(map#2)*(Green material)] which is equivalent to inverse(map#1)*(Blue material)+(map#1)*inverse(map#2)*(Orange material)+(map#1)*(map#2)*(Green material)

whereas your setup with one V-Ray blend material does the following:

(map#2)*(Green material)+inverse(map#2)*[(map#1)*(Orange material)+inverse(map#1)*(Blue material)] which is equivalent to inverse(map#2)*inverse(map#1)*(Blue material)+inverse(map#2)*(map#1)*(Orange material)+(map#2)*(Green material)

and as you can see the three materials have different weights in that case. It might be possible to shuffle things around so that you can still get the same result with one V-Ray blend material.

I hope this helps.

Best regards,
Vlado

Oh, crazy maths =) I understand what do you mean, but I don't understand how to shuffle this things and make the right result with one Vray Blend =) he-he =) With your formulas I see the difference, but I don't fully know the all of V-Ray secrets and which map can help to make the same variant =) because a simple change in the position of the nodes doesn't help. and I don't understand what I should to do =)

I'm not so good with mathematics, maybe you can create screenshot of this material or change my scene and send your variant? =)

So for me - the easiest way to use 2 vray blends =) ahahah =)

Thank you, Vlado =)

Best regards,
Andrew.