I was beginning to wonder how bright a color can go.
I have created an emissive procedural texture to be used in a star map. The texture gets a "brighntess"-value (0.0 to approx 1.2) as a parameter, that is then handled in a expression module like "1 + input1 * 20.0 + pow(input1, 2.0) * 30.0". This is then connected to the color function / scale to give the stars a powerfur shine enough (and the scaled value goes to the emissive channel)
It's basically working fine, but I was beginning to wonder how bright I can go? Is there a limit where the emissive-channel gets saturated?
-P-
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There's no fundamental limit, but in practice there may be limits depending on how you're using it. The brightness of a pixel in the final rendered image cannot be brighter than 1.0 (unless you save as an HDR image), so for purposes of directly viewing the texture there's no benefit to values brighter than that. Presumably you're doing this because you want the sky to illuminate other objects? When rendering, you may want to decrease the "min ray intensity" value in the Advanced Options window. Any ray that has an intensity less than that is skipped, since it is assumed to make negligible difference to the final image. The default value is 0.01, which makes sense if all your light sources have intensities of around 1.0 or less. But if a ray with intensity 0.01 hits an emissive surface with brightness 20, then it will contribute 0.2 to the pixel color which is still very significant.
Peter
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That's right. Illumination (one way or another) is the point.
The idea is that each star is (or could be) smaller than a pixel and then antialiasing makes them visible. Then I have been playing with view angle, tranparency and emissivity … The thing is relying on the HDR properties of the renderer for example so, that though most of the (16000 or so) stars are rather dim, the brightest of them are emphasized by the glow filter (which does not do much to pixels with brightness below 1).
-P-
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Hi!… Still on the same thing.
I was beginning to wonder how bright a color can go.
I have created an emissive procedural texture to be used in a star map. The texture gets a "brighntess"-value (0.0 to approx 1.2) as a parameter, that is then handled in a expression module like "1 + input1 * 20.0 + pow(input1, 2.0) * 30.0". This is then connected to the color function / scale to give the stars a powerfur shine enough (and the scaled value goes to the emissive channel)
It's basically working fine, but I was beginning to wonder how bright I can go? Is there a limit where the emissive-channel gets saturated?
-P-
There's no fundamental limit, but in practice there may be limits depending on how you're using it. The brightness of a pixel in the final rendered image cannot be brighter than 1.0 (unless you save as an HDR image), so for purposes of directly viewing the texture there's no benefit to values brighter than that. Presumably you're doing this because you want the sky to illuminate other objects? When rendering, you may want to decrease the "min ray intensity" value in the Advanced Options window. Any ray that has an intensity less than that is skipped, since it is assumed to make negligible difference to the final image. The default value is 0.01, which makes sense if all your light sources have intensities of around 1.0 or less. But if a ray with intensity 0.01 hits an emissive surface with brightness 20, then it will contribute 0.2 to the pixel color which is still very significant.
Peter
That's right. Illumination (one way or another) is the point.
The idea is that each star is (or could be) smaller than a pixel and then antialiasing makes them visible. Then I have been playing with view angle, tranparency and emissivity … The thing is relying on the HDR properties of the renderer for example so, that though most of the (16000 or so) stars are rather dim, the brightest of them are emphasized by the glow filter (which does not do much to pixels with brightness below 1).
-P-