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Technical Discussion » pbr diffuse multed by 2
- mikeo
- 11 posts
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Technical Discussion » pbr diffuse multed by 2
- mikeo
- 11 posts
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I was wondering if anyone could shed some light on why the default pbr diffuse node multiplies the diffuse result by 2? below is the code from ‘pbrdiffuse’.
vector $tnN = $isconnected_nN ? $nN : normalize(N);
if ($drough > 0)
{
$f = 2.0*diffuse($tnN, $drough, “label”, $label);
}
else
{
$f = 2.0*diffuse($tnN, “label”, $label);
}
thanks
vector $tnN = $isconnected_nN ? $nN : normalize(N);
if ($drough > 0)
{
$f = 2.0*diffuse($tnN, $drough, “label”, $label);
}
else
{
$f = 2.0*diffuse($tnN, “label”, $label);
}
thanks
Technical Discussion » AttribVOP: the best solution for read attributes from grid?
- mikeo
- 11 posts
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“inside of iteration”
Are you using attributeVop to iterate over the points on your grid?
If so,
Cd is bound for you…. There is a ‘Cd’ input and Color output.
M
Are you using attributeVop to iterate over the points on your grid?
If so,
Cd is bound for you…. There is a ‘Cd’ input and Color output.
M
Technical Discussion » MIS, Microfacets and Mantra
- mikeo
- 11 posts
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So I am currently attempting to implement the Beckmann Microfacet BSDF model with the new cvex_bsdf functionality. I am almost there but am having some issues with bias between bsdf and light sampling.
I have setup a Veach test using the default ‘blinn’ pbr specular model and pbr diffuse to see how the pathtracer mis bias is working..
Attached are the results. The question i have is about the variance and noise in the ‘bsdf only’ -1 bias image….
The cvex_bsdf docs state…. “If the rendered results are the same (apart from noise) with values of -1, 0, and 1, your shader is bias-free.”
Is the variance from that image compared to the the bias 0 image within the expected threshold? I seems pretty good apart from the high roughness and small light panel in the bottom left.
I am having the opposite affect….
My surface bsdf sampling is fine but light sampling is very noisy…..
Setting the ‘pdf’ export in the bsdf_sample shader to any random value does not affect the rendered result… After looking in the path_tracer code i see that ‘hitpdf’ is only used in the shadowing function and does not seem to affect the MIS bias…
Wondering where that value is used?
I have setup a Veach test using the default ‘blinn’ pbr specular model and pbr diffuse to see how the pathtracer mis bias is working..
Attached are the results. The question i have is about the variance and noise in the ‘bsdf only’ -1 bias image….
The cvex_bsdf docs state…. “If the rendered results are the same (apart from noise) with values of -1, 0, and 1, your shader is bias-free.”
Is the variance from that image compared to the the bias 0 image within the expected threshold? I seems pretty good apart from the high roughness and small light panel in the bottom left.
I am having the opposite affect….
My surface bsdf sampling is fine but light sampling is very noisy…..
Setting the ‘pdf’ export in the bsdf_sample shader to any random value does not affect the rendered result… After looking in the path_tracer code i see that ‘hitpdf’ is only used in the shadowing function and does not seem to affect the MIS bias…
Wondering where that value is used?
Technical Discussion » cvex_bsdf() vtransform
- mikeo
- 11 posts
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I was wondering if anyone is having the same issue as me….
Using vtransform in my cvex_bsdf evaluation function does not seem to work. I am trying to transform ‘u’ from space:camera to spacebject.
If i pass in a matrix with the camera to object rotation(by using dihedral in vex)- then i am able to transform it.
Is this the correct behaviour? do “space:foo” lookups work in cvex_bsdf functions?
thanks
M
Using vtransform in my cvex_bsdf evaluation function does not seem to work. I am trying to transform ‘u’ from space:camera to spacebject.
If i pass in a matrix with the camera to object rotation(by using dihedral in vex)- then i am able to transform it.
Is this the correct behaviour? do “space:foo” lookups work in cvex_bsdf functions?
thanks
M
Houdini Lounge » prman rendering losing geo
- mikeo
- 11 posts
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Houdini Lounge » prman rendering losing geo
- mikeo
- 11 posts
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I have a ‘tube’ sop with a ‘cap’ sop attached using the ‘end cap shared’ as U cap.
When i render with mantra the geo is rendered as expected. When i run a prman render with an ri_plastic shader attached the end caps are not rendered but the tube is.
Has anyone seen this behaviour before. thanks
When i render with mantra the geo is rendered as expected. When i run a prman render with an ri_plastic shader attached the end caps are not rendered but the tube is.
Has anyone seen this behaviour before. thanks
Houdini Lounge » Importing Audio
- mikeo
- 11 posts
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Houdini Lounge » Importing Audio
- mikeo
- 11 posts
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I am trying to use the file CHOP to import a .wav file on linux, but keep getting:
Loading from stream failed ( ref: (null))
File not found.
And yes the file is there and plays fine. :wink:
any idas?? thanks
Loading from stream failed ( ref: (null))
File not found.
And yes the file is there and plays fine. :wink:
any idas?? thanks
Houdini Lounge » COPS image lookup
- mikeo
- 11 posts
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Houdini Lounge » COPS image lookup
- mikeo
- 11 posts
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I am fairly new to houdini and am wanting to move some points based on an image look up. I have thought of a expression to do it but need to get at the parameters of the pixel or another COP, e.g. image size and pixel channel values.
For example, I what to be able to say in the expression: Move the point up the Y based on the red channel value at this x,y coord. Is there a COP that i can reference these values from?
Thanks
For example, I what to be able to say in the expression: Move the point up the Y based on the red channel value at this x,y coord. Is there a COP that i can reference these values from?
Thanks
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