Light-angle-dependant color

[stratik]

Hello all,

I'm trying to get an effect in maya where the color of something changes in relation to the light's angle. --Kinda like the facing ratio, but where it deals with the angle of the normals in relation to the LIGHT, instead of the angle of the normals in relation to the CAMERA. I've been messing around with the light info utility for a while, but without results.

Thanks for your help.

Ricky
DesignDawg

[pixho]

Hi,

One example for a dir light:

• Create a samplerInfo, a vectorProduct, and a ramp.

Connect the rayDirection of the samplerInfo to the input1 of the vectorProduct, then connect the lightDirection of the dir light (under lightData), let the operator to dot product, then connect the outputX of the vector to the u or vcoord of a ramp.
Now, if you rotate the dir light, the ramp will be driven by the rayDirection of the light.

To insert more lights, duplicate and conenct as many vectorProducts as you have lights.

Hope this helps.

Emmanuel

Emmanuel Campin
Lighting & shading TD
www.pixho.com

[stratik]

Man, you rock. --And you keel hours that are convenient for me, too! I'll try that first ting tomorrow. For now, I just fixed my "metallic bug" shader. Thanks for your input in there as well, alhough I ended up fixing it exactly as I thought of before I posted. I guess I should have tried it first!

Ricky
DesignDawg

[wcy93]

so how do you go about setting up the connections for multiple lights? if you have 2 lights, you have 2 vector products, and a sampler info, so how do you get both the vector products plugged into the ramp?

I don't geddit.
thanks.

[pixho]

Mmmh, I'm not sure. I told you that you need as many vectorProducts as you have lights, but I think you need one more vp to determine the dotProduct of both lightDirections of your lights.

Make the connections like I said (for 1 light)
If you want to insert one more light, create 2 vectorProducts
Make again the conenctions between the samplerInfo and the 2nd vectorProduct, connect the lightDirection of your 2nd light into the input2 of the 2nd vp again.
Then connect the output of both vectorProducts into the input1 and 2 of the third vectorProduct.
Ah, forgot to tell you to insert between the ramp and the 3rd vp a setRnage or a clamp node to clamp the values from 0 to 1, then connect the outValueX (of the clamp) into the u or vcoord of the ramp.

This should work, but like I said, I'm not quite sure if the network is correct.

So to sum this up, you need one vp per light to determine it's dotProduct between its lightDirection and rayDirection, then another vp to make the dorProduct of each dotProduct of your lights.

Hope this make sense

Emmanuel

Emmanuel Campin
Lighting & shading TD
www.pixho.com

[wcy93]

but a dot product gives you a scalar result, not a vector... so you wouldn't be able to put the output of a vector dot product into the input of another vp. at least not sensically.

i was thinking that maybe if you setup each light, with clamps and no ramp, and then added them together maybe (i think just putting them in a layered texture, with mode add on, should work). that would probably give you the behavior you wanted. you'd probably need another clamp after the layered texture before it goes into the ramp though.