Facingratio Node

[eky]

hi,

i'm looking for a node which make the same things than a sampler info.
i'am wan't to know the facingratio of an object for an locator, or a camera...

thanks a lot.
eky

[joojaa]

No problem best not do this in api as you'd need to develop it 3 times once for the hw shader (wich unfortunately thsi does not do for you) once for maya sw and once for mr, maya can already do this with its available nodes. Basically ratio is just normal dot towards whatever you need vector. So im going to demonstrate this on a surface shader omit it and plug vectors or whatever you need.

Execute following mel in your script editor.

CODE
{
$shd=shadingNode -asShader surfaceShader;
$VectorMatrix=shadingNode  -n "vectorMatrix" -asUtility vectorProduct;
setAttr ($VectorMatrix+".operation") 3;
$dotProd=shadingNode -n "Dot" -asUtility vectorProduct;
$sampler=shadingNode -n "samplerData" -asUtility samplerInfo;
// if the direction is fixed you can omit this and precalculate the normal
// into camera space instead its speeds thinsg up slightly
connectAttr -f ($sampler+".normalCamera") ($VectorMatrix+".input1");
connectAttr -f ($sampler+".matrixEyeToWorld") ($VectorMatrix+".matrix");
connectAttr -force ($VectorMatrix+".output") ($dotProd+".input1");
connectAttr -f ($dotProd+".output") ($shd+".outColor");

//change this to either a vector field form surface point to your
//point of keep it fixed.
setAttr($dotProd+".input2") 0 1 0;
}

[eky]

Very nice Jooja, your code is working well! thank you very much.
I believe I could continue with my project.

I have two little problems.
I never heard of matrix. I don't know what is store in a matrix variable.
I have connected translate attributes of a locator to the input of your dot vector product. (it works, when I move the locator, the facing ratio follow the locator)
I think it's what i shoud to do !?

But I tried to connect the result of your dot vector product to the Baldness of a fur, and it doesn't work.
I hope you could help me.

thanks.

eky

[joojaa]

Yes it wont work, because it must be a texture, and a shading network ustilizing normal info like this is neither (the normal sint known at texture time).

Bake the texture down!

PS: a Lambert shader attached to 1 light with diffuse set to 1 is actually the same thing!

[heron3d]

Hi Joojaa,
This is excercise and it has to do with the facing ratio and shader programming. The interp plugin example replicates facing ratio attr.

The example creates 2 attrs that refer to the view vector and the surface normal

aNormalCamera = nAttr.createPoint( "normalCamera", "n");
aPointCamera = nAttr.createPoint( "pointCamera", "p");

In the compute method the data is input and used in this equation...

MFloatVector& surfNorm = block.inputValue( aNormalCamera ).asFloatVector();
MFloatVector& viewVector = block.inputValue(aPointCamera).asFloatVector();

// Normalize the view vector
viewVector.normalize() ;

// find dot product
float scalarNormal = (viewVector.x * surfNorm.x) + 
	(viewVector.y * surfNorm.y) +
	(viewVector.z * surfNorm.z);

// take the absolute value
if (scalarNormal < 0.0) scalarNormal = -scalarNormal;

And it continues...The resultColor is positioned in the output handle.

What is confusing me is surfNormal and viewVector never refer to anything. When I create shader and apply to sphere, it works ok without any input connections. How is the surfNom attr aware of the surface. It seems like a regular MFloatVector attr with descriptive name but unaware of anything else.

What I would like to do is get the normal of the point being sampled in world space but I can't figure out how to do this. Would I have to input geometry? Or to put more succinctly (english fails at night) - how do I access render cache values so I can manipulate them?

Nikos

[joojaa]

QUOTE(heron3d @ 12/27/07, 06:13 AM) [snapback]278740[/snapback]
What is confusing me is surfNormal and viewVector never refer to anything. When I create shader and apply to sphere, it works ok without any input connections. How is the surfNom attr aware of the surface. It seems like a regular MFloatVector attr with descriptive name but unaware of anything else.

thets because maya broadcasts certain global attributes, this includes time for deformers amd a a nuber of things for shading nodes. Wich is why many nodes have inputs that don't lead anywhere but they are connected to these broadcasts. (if you look at sampler info it has inputs too).

THis feature makes the node reference one of the most valuable programming information sources in maya

QUOTE
What I would like to do is get the normal of the point being sampled in world space but I can't figure out how to do this. Would I have to input geometry? Or to put more succinctly (english fails at night) - how do I access render cache values so I can manipulate them?

Multiply the normal you get with inverse camera matrix, (see the renderer works in camera space, so for the rendering engine the camera IS the world), or with the object inverse world if you ask the local normal.

[heron3d]

ok but how do I get the inverse camera matrix? Is that one of the attrs I would have to connect in maya? So lets say I wanted to get the position of the point being sampled, be it in world or camera space, How do I query that value?

nikos

[heron3d]

Problem solved,

I just found apendix C in the API docs. It list all the shading attrs I was looking for.

Thanks Joojaa

nikos

[heron3d]

OK, so this works in Maya with utility nodes.

As for the API...

CODE
MFloatVector surfNormal
MFloatMatrix eyeToWorldM

//I get the surface normal in world space
surfNorm.transformAsNormal(eyeToWorldM);

//I input another arbitrary matrix that is writable and connectable
MFloatMatrix myInputMatrix;

//now i want the surfNormal in the inputMatrix object space
surfNorm.transformAsNormal(myInputMatrix);

MFloatVector pointingVector(0.0, 0.0, 1.0 );//in Z

//I want the pointing vector in the inputMatrix object space
pointingVector.transformAsNormal(myInputMatrix);

//now I want the dot product
float myDotVal = (pointingVector * surfNorm.x) +
        (pointingVector * surfNorm.y) +
        (pointingVector.z * surfNorm.z);

MFloatVector resultColor (myDotVal, myDotVal, myDotVal);

outColor = resultColor;

and so on..

In maya, I create surface shader. I connect custom facing ratio node outColor to outColor of surface shader.
I then connect the pointing object (cone) worldMatrix to myInputMatrix.

Maya slows down and facing ratio constanly aligns towards active camera and not pointing object.

anyone have ideas?

Nikos

[heron3d]

This is what it prints out

matrixEyeToworld =
[[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]
[b]This is the initial pointing vector[/b]
[0, 0, 1]
This is the pointing vector transformed by inMatrix
[0, 0, 1]
[b]This is the pointing vector transformed by W2E[/b]
[0, 0, 1]
This is the initial surfNorm
[0.145138, -0.165942, 0.975397]
[b]This is the surfNorm transformed by E2W[/b]
[0.145138, -0.165942, 0.975397]
This is the surfNorm transformed by inMatrix
[0.145138, -0.165942, 0.975397]
[b]this is the scalarNormal [/b]
0.975397
This is the resultColor
[0.975397, 0.975397, 0.975397]

inMatrix =
[[0.920478, -0.017604

The eyeToWorld and worldToEye are all identity matrices???????
This is how I declare the attributes

CODE
aInMatrix = nMAttr.create("inMatrix", "inm", MFnMatrixAttribute::kFloat, &stat);
        McheckErr( stat, "cannot create inMatrix attribute" );
    nMAttr.setKeyable(false);
    nMAttr.setStorable(false);
    nMAttr.setReadable(false);
    nMAttr.setWritable(true);
    nMAttr.setConnectable(true);
    nMAttr.setHidden(true);

    aMatrixEyeToWorld = nMAttr.create("matrixEyeToWorld", "etw", MFnMatrixAttribute::kFloat, &stat);
        McheckErr( stat, "cannot create eyeToWorldMatrix attribute" );
    nMAttr.setKeyable(false);
    nMAttr.setStorable(false);
    nMAttr.setReadable(true);
    nMAttr.setWritable(false);
    nMAttr.setConnectable(true);
    nMAttr.setHidden(true);

    aMatrixWorldToEye = nMAttr.create("matrixWorldToEye", "wte", MFnMatrixAttribute::kFloat, &stat);
        McheckErr( stat, "cannot create worldToEyeMatrix attribute" );
    nMAttr.setKeyable(false);
    nMAttr.setStorable(false);
    nMAttr.setReadable(true);
    nMAttr.setWritable(false);
    nMAttr.setConnectable(true);
    nMAttr.setHidden(true);

    aPointCamera = nAttr.createPoint( "pointCamera", "p", &stat);
        McheckErr( stat, "cannot create pointCamera attribute" );
    nAttr.setStorable(false);
    nAttr.setHidden(true);
    nAttr.setReadable(true);
    nAttr.setWritable(true);

    aNormalCamera = nAttr.createPoint( "normalCamera", "n", &stat);
        McheckErr( stat, "cannot create normalCamera attribute" );
    nAttr.setStorable(false);
    nAttr.setHidden(true);
    nAttr.setReadable(true);
    nAttr.setWritable(true);

What I am missing?

[joojaa]

no maya at hand but i think it must be writable and storable inorder for the data to pass in. Otherwise the data originates form you. Its still a inbound connection even if you dont connet it to anything.

Also they will not yield any sabe value outside rendering context.

[heron3d]

QUOTE(Joojaa @ 12/27/07, 12:37 PM) [snapback]278781[/snapback]
no maya at hand but i think it must be writable and storable inorder for the data to pass in. Otherwise the data originates form you. Its still a inbound connection even if you dont connet it to anything.

Also they will not yield any sabe value outside rendering context.

This is excercise. Here is the interesting thing. You can access the matrixWorldToEye - EyeToWorld with the dataHandle asMatrix NOT as floatMatrix. But if you want to postmultiply surfNormal which is a floatVector, by MMatrix which is a double you loose data, hence the identity matrices. The question becomes, can I make my surfNormal attribute a double and simply work with doubles? I changed my attr's dataTypes to all doubles. I inputValue.asVector (not floatVector) and also output to dataHandle asVector(). It should work, yes? I load plugin and Maya crashes.

here is code
CODE
//input values
MVector& surfNorm = block.inputValue( aNormalCamera, &stat ).asVector();//NOT .asFloatVector();

MMatrix& inMatrix = block.inputValue( aInMatrix, &stat).asMatrix();// MMatrix IS DOUBLE NOT FLOAT

MMatrix& matrixWorldToEye = block.inputValue( aMatrixWorldToEye, &stat).asMatrix();

MVector pointingVector(0.0 ,0.0 ,1.0 );
    //DISPLAY_INFO(pointingVector, "This is the initial MVector pointing vector")
pointingVector = inMatrix * pointingVector;
    //DISPLAY_INFO(pointingVector, "This is the pointing vector multiplied by inMatrix")
pointingVector= matrixWorldToEye * pointingVector;
    //DISPLAY_INFO(pointingVector, "This is the pointing vector multiplied by W2E")

double scalarNormal =     (pointingVector.x * surfNorm.x) +
                (pointingVector.y * surfNorm.y) +
                (pointingVector.z * surfNorm.z);

MVector resultColor(scalarNormal, scalarNormal, scalarNormal);

MDataHandle outColorHandle = block.outputValue( outColor );
        MVector& outColor = outColorHandle.asVector();//NOT .asFloatVector();
        outColor = resultColor;
        outColorHandle.setClean();

//DECLARE ATTRS
CODE
aMatrixEyeToWorld = nMAttr.create("matrixEyeToWorld", "etw", MFnMatrixAttribute::kDouble, &stat);
        McheckErr( stat, "cannot create eyeToWorldMatrix attribute" );
    nMAttr.setKeyable(false);
    nMAttr.setStorable(true);
    nMAttr.setReadable(true);
    nMAttr.setWritable(true);
    nMAttr.setConnectable(true);
    nMAttr.setHidden(true);

aNormalCamera = nAttr.createPoint( "normalCamera", "n", &stat);
        McheckErr( stat, "cannot create normalCamera attribute" );
    nAttr.setStorable(false);
    nAttr.setHidden(true);
    nAttr.setReadable(true);
    nAttr.setWritable(true);

If normalCamera attr is intrinsically a float and we input with data handle asVector which is doubles,
then we are promoting float to double which is ok, yes?

Why crash???!!!

Nikos

[joojaa]

Yes, but does it really matter. Anyway for your rendering need it dont really matter.

you allways loose data! Anyway maya renders color as float not double float so you cant really access the values as doubles either. But you can cast the float as a double yes. but you'd round out the result at the end anyway.

Now since this float gets converted to 16 max bits anyway you loose precision form that anyway.

PS: besides even your tessellation isnt this precicie.

[heron3d]

I've gone back to all floats...MFloatVector, MFloatMatrix etc. All shader plugin examples use floats. It should work. My code is right out of the other examples. The flameShader even inputs a placement matrix as kFloat. The question then becomes...why are they all identity matrices. They don't work. I use them to post multiply with MFloatVectors result is same. I can attach the the cpp file if necessary.

nikos

[joojaa]

Probably because you think the report of node network gui time is the same as the report render time. The camera isnt known untill you start shading something. And the preview spheres hawe a bit special camera relation.

I dont think the rpoblem is necessarily in your code but rather how you expect it to work.

[heron3d]

I input everything as floats and this is result. The matrices have very funny values...

inMatrix prints =
[[2.17256e-021, 1.83141, 1.64484e-023, -1.73584], [-4.54465e+007, -1.65477, 0, 0], [-4.86943e+020, 1.74604, -2.05807e+008, 1.84261], [5.03907e-025, -1.09566, 0, 0]]

What is the meaning of 4.86943e+020

MFloatVector pointingVector(0.0f ,0.0f ,1.0f );
This is the initial MVector pointing vector
[0, 0, 1]

pointingVector *= inMatrix;

This is the pointing vector multiplied by inMatrix prints
[-4.86943e+020, 1.74604, -2.05807e+008]

pointingVector.normalize();
This is the pointing vector normalized prints
[-0, 0, -0]

pointingVector *= matrixWorldToEye;

float scalarNormal = (pointingVector.x * surfNorm.x) +
(pointingVector.y * surfNorm.y) +
(pointingVector.z * surfNorm.z);

floatVector resultColor (scalarNormal, scalarNormal,
scalarNormal);

This is screengrab jpeg: facingRatioScreengrab
nikos