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What's the story of the "matte"? that thing emits light!

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What's the story of the "matte"? that thing emits light!

Unread postby lookdev » Thu Mar 14, 2019 2:01 pm

That thing called "matte" seems to emit light even when there is absolutely no single light whatsoever in the scene.

I bumped into this by accident when I was testing terrain texturing using matte with texture map. I've noticed the matte on the terrain didn't seem to react to light tweaking, I thought let's delete all the lights, the terrain is still textured, visible as if it was daylight.
Then I applied a matte on a box, and it starts emitting light, lighting parts of the terrain (I had removed the terrain matte and kept a silver on the sphere).
The silver sphere reflects the lights of the box. And there is no light in the scene.
Is this normal, like intended? (I'm using version 4)

I did check twice before posting this, I actually even rebooted the computer, done it again from a blank scene.
Am I the last one to realise matte emits light? well if it does, I can make good use of it, but I'd like to be able to tweak how much light it emits.
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Re: What's the story of the "matte"? that thing emits light!

Unread postby dboude » Thu Mar 14, 2019 2:18 pm

Yes, matte shader emits light. If you want to control the emission just tweak the brightness of the matte color.

On the other side if you want the object to be a matte object and not participate in the secondary rays, check the Matte Object attribute on the object level.

Cheers
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Re: What's the story of the "matte"? that thing emits light!

Unread postby Kramon » Thu Mar 14, 2019 2:54 pm

so what is the diff between matte and emission? O_o
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Re: What's the story of the "matte"? that thing emits light!

Unread postby lookdev » Thu Mar 14, 2019 3:16 pm

dboude wrote:Yes, matte shader emits light. If you want to control the emission just tweak the brightness of the matte color.

On the other side if you want the object to be a matte object and not participate in the secondary rays, check the Matte Object attribute on the object level.

Cheers


So what should I use for a terrain (I have a terrain mesh and a texture)? I need the terrain to "respond" to light tweaking (hdri, distant light).
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Re: What's the story of the "matte"? that thing emits light!

Unread postby lookdev » Thu Mar 14, 2019 3:18 pm

Kramon wrote:so what is the diff between matte and emission? O_o

A question about your question: you referred to emission as emitter material right? or is there a parameter somewhere in the object?
Last edited by lookdev on Thu Mar 14, 2019 3:21 pm, edited 1 time in total.
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Re: What's the story of the "matte"? that thing emits light!

Unread postby Kramon » Thu Mar 14, 2019 3:20 pm

i don't understand... for me matte was shader that just display raw value... no emission no recaveing shadows... just like you would paste in photoshop a texture on top of everything.... and emission is just emission shader y/n?
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Re: What's the story of the "matte"? that thing emits light!

Unread postby lookdev » Thu Mar 14, 2019 3:25 pm

Kramon wrote:i don't understand... for me matte was shader that just display raw value... no emission no recaveing shadows... just like you would paste in photoshop a texture on top of everything.... and emission is just emission shader y/n?


That's exactly what I would expect indeed. Not sure why does matte emit light, if an emitter material is already there. I would expect matte to be exactly what you said.
I can't use a matte for a terrain texture now, and I think using a standard material (to avoid emitting light) just to plug a terrain texture is an overkill.
At least I should be able to switch off the emitting from a matte.
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Re: What's the story of the "matte"? that thing emits light!

Unread postby dboude » Thu Mar 14, 2019 4:02 pm

It's historical. Matte Shader is evaluated in secondary rays. That's all.

Like I said If you want a matte object that is not evaluated in secondary rays just check matte object on geometry.

If you don't want your object to emit light uncheck "Is emitter" in the object attributes...
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Re: What's the story of the "matte"? that thing emits light!

Unread postby dboude » Thu Mar 14, 2019 4:08 pm

And if you use a matte material to shade your terrain you won't be able to light it !!!
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Re: What's the story of the "matte"? that thing emits light!

Unread postby lookdev » Thu Mar 14, 2019 4:30 pm

Thank you. It's clear about the matte.
Which material would you use for a terrain texture (png from world machine...)?
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