Blackbody "test" scene

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Borgleader
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Blackbody "test" scene

Post by Borgleader » Fri Aug 07, 2009 9:29 am

Well it's not really a test scene, I was just trying to illustrate the effect of changing the temperature value on a blackbody material. I think it's a really useful material and it's something that some people may have trouble understanding so I thought I'd make it easier to understand. A picture is worth a 1000 words is it not? :wink:

So I created a hole bunch of emitters and started at 1500 degrees to 8500 in increments of 500 degrees. I think the result not only illustrates this effect quite well but I think the presentation is rather nice as well if I do say so myself.

Comments/Thoughts?
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neo0.
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Re: Blackbody "test" scene

Post by neo0. » Fri Aug 07, 2009 11:31 am

Interesting concept. It would be nice with a higher polycount and thus more gradual temp changes, but other than that, it looks nice.

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Borgleader
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Re: Blackbody "test" scene

Post by Borgleader » Fri Aug 07, 2009 11:42 am

neo0. wrote:Interesting concept. It would be nice with a higher polycount and thus more gradual temp changes, but other than that, it looks nice.
IIRC there are 15 emitters in there. Unless youre talking about the ring, increasing the poly count wont help much.
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CTZn
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Re: Blackbody "test" scene

Post by CTZn » Fri Aug 07, 2009 11:58 am

Comments/Thoughts?
Yep. You could blend two emitters over one surface and get a cheaper version of the effect, meaning it's not as nice as your example :)

Funny, I was looking at some sodium lamps tonight :)

edit: woops, the image went away, back now !
Attachments
blend_em.jpg
1800K gain 10
8500K gain 0.0002
Indigo's default emittance, blend texture is a linear ramp, black to white.
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neo0.
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Re: Blackbody "test" scene

Post by neo0. » Fri Aug 07, 2009 2:16 pm

You know me.. I can't resist screwing around with indigo :)

Not quite the effect I was shooting for, but I think it turned out neat, never the less. I have a ring with 50 different blackbody materials.
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Borgleader
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Re: Blackbody "test" scene

Post by Borgleader » Fri Aug 07, 2009 2:42 pm

CTZn wrote:
Comments/Thoughts?
Yep. You could blend two emitters over one surface and get a cheaper version of the effect, meaning it's not as nice as your example :)

Funny, I was looking at some sodium lamps tonight :)

edit: woops, the image went away, back now !
Thats a pretty cool light :) I may use it in a scene! Could I have a SS of your mat settings? :)
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CTZn
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Re: Blackbody "test" scene

Post by CTZn » Sun Aug 09, 2009 12:13 am

I assume that you are asking for a screen capture of the blender interface Borgleader, but I don't use blender. I can share the materials xml:

Code: Select all

<material>
	<name>lambert2SG</name>
	<diffuse>
		<albedo>
			<constant>
				<rgb>
					<rgb>0 0 0</rgb>
					<gamma>2.200000048</gamma>
				</rgb>
			</constant>
		</albedo>
		<layer>0</layer>
		<base_emission>
<!--spectrumNode-->
			<constant>
				<blackbody>
					<temperature>8500</temperature>
					<gain>0.0001999999949</gain>
				</blackbody>
			</constant>
		</base_emission>
	</diffuse>
</material>

<material>
	<name>lambert3SG</name>
	<diffuse>
		<albedo>
			<constant>
				<rgb>
					<rgb>0 0 0</rgb>
					<gamma>2.200000048</gamma>
				</rgb>
			</constant>
		</albedo>
		<layer>0</layer>
		<base_emission>
<!--spectrumNode-->
			<constant>
				<blackbody>
					<temperature>1800</temperature>
					<gain>10</gain>
				</blackbody>
			</constant>
		</base_emission>
	</diffuse>
</material>

<material>
	<name>layeredShader1SG</name>
	<blend>
		<texture>
			<uv_set>default</uv_set>
			<path>C:/work/3d/archi/MarxDo/Indigo/ramp1-pTorus1.png</path>
			<exponent>1</exponent>
			<b>1</b>
			<c>0</c>
		</texture>
		<blend>
			<texture>
				<texture_index>0</texture_index>
			</texture>
		</blend>
		<a_name>lambert2SG</a_name>
		<b_name>lambert3SG</b_name>
	</blend>
</material>
... but it's simpler to say that there are two emitting materials blending along the meshe's length, by using a black to white ramp as blending texture (the mesh has no height, it's one row of faces). Since we are interpolating two values it's no as accurate as the multiple meshes option. Furthermore the light emitted by the "cold" blackbody has been amplified by a factor 50,000 for aesthetical reasons.

Did I miss your point Borgleader ?
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Borgleader
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Re: Blackbody "test" scene

Post by Borgleader » Sun Aug 09, 2009 2:14 am

Nope, you pretty much answered it pretty well :) However, I was aware that you aren't a Blenderhead when I asked for a screenshot ;)

Thanks a lot!
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