Energy Orb
- Thread starter ZooHead
- Start date
ZooHead
0
Just waking up- 5 am, a little snow on the ground and the prospect of change is in the air.
Some cool possibilities for sure.
I'll post it later but hooking up the EYE out to the Emmisive channel looks cool.
Don't know what it does but it adds some highlights at the edges.
I need to study your explanations of the nodes more. Will you make a pdf soon?
Some cool possibilities for sure.
I'll post it later but hooking up the EYE out to the Emmisive channel looks cool.
Don't know what it does but it adds some highlights at the edges.
I need to study your explanations of the nodes more. Will you make a pdf soon?
MonkeyT
0
Create a default scene. Put a sphere which is colored using the Eye property right next to a sphere which is colored using the Normal property, and render it. What appears to happen with the Normal object as you rotate around the pair is:
ª the closer the normal vector of each polygon is to matching the y-axis (y > 0), the more green is reflected.
ª the closer the normal vector of each polygon is to matching the x-axis (x > 0), the more red is reflected.
ª the closer the normal vector of each polygon is to matching the z-axis (z > 0), the more blue is reflected.
Because we're dealing with color vectors being rendered, I assume the opposite directions result in negative values, so those all render as black.
Now, if you imagine a vector coming from the Center of Rotation of the Eye object to the camera, you get the entire object being colored using the same rules. ( Rotating the object affects the Normal coloration - it uses relative space, but does not affect the Eye object - it seems to use global space.)
I have no idea what terminology is used to describe this.
ZooHead
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I'll have to try that out.
You know I think the I•N is something called a dot product.
This is something I was taught in physics but never learned, also cross product.
Dot product is vector multiplication, cross product is vector addition if I'm remembering correctly.
That would mean if I = incidence of light vector multiplied by N = normal vector i guess.
I could never get my head around multiplying vectors, adding vectors I think I understand.
You know I think the I•N is something called a dot product.
This is something I was taught in physics but never learned, also cross product.
Dot product is vector multiplication, cross product is vector addition if I'm remembering correctly.
That would mean if I = incidence of light vector multiplied by N = normal vector i guess.
I could never get my head around multiplying vectors, adding vectors I think I understand.
MonkeyT
0
THAT'S IT! I've always read Cheetah3D's label as an abbreviation: I - N. It actually is I • N ( the Dot Product of the Incidence Vector and the Normal Vector )! Darned tiny type! Now the name makes sense to me!
The Incidence Vector is a unit vector indicating the path of the light being reflected to the Camera from the surface/polygon.
The Normal Vector is a unit vector that its perpendicular to the surface/polygon.
A Dot Product ( A • B ) tells you how far the first vector ( A ) reaches in the direction of the second vector ( B ).
So given that both I & N are 1 unit long: If N reflects directly back along the length of I, the value of the Dot Product is 1. If N is perpendicular to the length of I, the value of the Dot Product is 0!
Mathematically, the Dot Product produces another vector, so it could be a negative value, but here, the Incidence must strike the front of the polygon, so the angle between it and the Normal ( called the Angle of Incidence ) can never be greater than 90° - so the value can never be less than 0.
A fun side effect: since this value is literally determined by the interaction between the raytracing vector from the camera and the surface of the polygon, the value will always be determined the same way, even if you are viewing a reflection of the back of that same object. Its reflection will render as if your camera were viewing the object from the surface of the mirror - so if you use the I • N value to create a transparency map, you won't see the same geometry in the reflection.
