surfaceLuminance Node behavior query

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  11 November 2003
Question surfaceLuminance Node behavior query

I am trying to create a relatively simple shader network in Maya that will shade a simple sphere with a dynamically changing Earth shader, one half daylight and one half night. The night texture has all of the city lights visible but no real colour information.

I am using a Layered Shader with two layers, one for the night and one for the day. The night layer has a Ramp (mapped to V) with a surfaceLuminance node connected to the V value, the ramp is then connected to the Transparency attribute of the night earth shader. This should work in theory.

However in practice it doesn't seem to want to, I am not quite sure why. Can anyone suggest why this strange effect is happening?

  11 November 2003
If I am to guess, I'd say that the luminance in the circular region of error is going beyond 1.0, and your shader can't handle it. I'll bet your ramp is going to 0.0 when the v-index goes past 1.0.

I don't know a solution off-hand, though I've dealt with this problem in the past... Some things to try perhaps:
- play with "Default Color" on ramp?
- multiply the output of surfaceLuminance by a factor?
- adjust (lessen) light intensity?
- play with 2d texture placement settings?

Something will work...

- Matthew Durante
  11 November 2003

You could use a blendColor and a surfaceShader instead a layerShader.
Connect the surfaceLum to a setRange and set the Xvalues (oldMin, oldMax min and max to 0 and 1 to avoid the result looping (what you have done with your ramp))
Connect then the setRange.outValueX to the blender.

In the color1 connect your daylight texture/shader and color2 your night shader.

Create then a surfaceShader and connect the blender to it, then assign the surfaceShader to your sphere.

Et voila

Emmanuel Campin
Infographiste 3d - Maya
  01 January 2006
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