[Sidefx-houdini-list] grid gradation

François Duchesneau sidefx at trinix.ca
Thu Apr 17 08:47:03 EDT 2014


A bias is more like a gamma curve. Have a look at the gain vop too which 
is similar to a contrast.

When you do shader writing or geo deformer, you use these guys all the 
time. Working in a normalized world is the way to go because so many 
tools is expecting a 0-1 range as its input.

Francois

herman lee wrote:
> Dear francois,
>
> Very well explained and I've tried it out. It works very well, never tried a
> bias vop before, both ramp and bias works! So a bias works similar to a
> ramp? I check the bias information, it has a formular for the gradation.
>
> Thanks!
>
> Cheers
> herman
>
> -----Original Message-----
> From: sidefx-houdini-list-bounces at sidefx.com
> [mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of François
> Duchesneau
> Sent: Thursday, 17 April, 2014 12:26 AM
> To: sidefx-houdini-list at sidefx.com
> Subject: Re: [Sidefx-houdini-list] grid gradation
>
> Sorry. I should have given more details about the normalize. What I mean is
> you have to remap the total width of the incoming geometry into a 0-1 value.
> You have to tell the fit function what is that value either by typing
> directly or promoting a parameter where you put an expression that reads the
> bounding box in X to have that automatically calculated even if you resize
> the grid.
>
> Try that.
> Plug the Global P into a vector to float Plug the X into a Fit Range. Set
> the Source Min and Source Max the coordinate of your grid in X. With a
> default grid that would be -5 and 5. This is the normalized range. In other
> words everything exists between 0 and 1.
> Plug this into a Bias Vop and promote the amount parameter for better
> interactivity.
> Plug the output into a fit that remap from 0,1 to -5,5.
> Create a Float to vector node and plug the output of the previous into the
> X. Plug the YZ output of the previous Vector to Float Vop in the YZ of this
> one.
> Plug the ouput into the P on outputt1.
>
> Play with the Bias parameter you promoted. The Bias Vop could be replaced
> with a Ramp Vop for better artistic control.
>
> Hope that helps
>
> herman lee wrote:
>   
>> Dear francois,
>>
>> I did tried, but it seems to be an output of a single line with points 
>> on it.
>>
>> I go from
>> position
>> (Global)>normalize>fval1(vectofloat)>ramp>floatovec>position(output)
>>
>> thanks
>>
>> cheers
>> herman
>>
>> -----Original Message-----
>> From: sidefx-houdini-list-bounces at sidefx.com
>> [mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of François 
>> Duchesneau
>> Sent: Wednesday, 16 April, 2014 11:27 PM
>> To: sidefx-houdini-list at sidefx.com
>> Subject: Re: [Sidefx-houdini-list] grid gradation
>>
>> One way is to put a vopsop after a grid and use a Bias Vop or a Ramp 
>> Vop to alter where the incoming X coordinate will be remapped to a 
>> different X. The key is to first remap your X value into a normalized 
>> 0-1 range before the bias or ramp and then remap it back.
>>
>> Let me know if it's not clear and I'll go into more details.
>>
>> Francois
>>
>> herman lee wrote:
>>   
>>     
>>> Hi all,
>>>
>>>  
>>>
>>> I want to create a grid with its coordinates gradually change from X 
>>> and Z, like the below image-
>>>
>>>  
>>>
>>> https://www.flickr.com/photos/7453761@N05/13895976915/
>>>
>>>  
>>>
>>>  
>>>
>>> I can manually group the points individually and transform row by 
>>> row, column by column, but this is not quite procedurally. Is there 
>>> any efficient way to create this effect or by expressions?
>>>
>>>  
>>>
>>>  
>>>
>>> Thanks
>>>
>>>  
>>>
>>> Cheers
>>>
>>> herman
>>>
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>>>   
>>>     
>>>       
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