Sampling color at vertexes



  • On 30/07/2014 at 01:45, xxxxxxxx wrote:

    User Information:
    Cinema 4D Version:   14 
    Platform:      Mac OSX  ; 
    Language(s) :     C++  ;

    ---------
    How can I sample the color of each vertex in a mesh?
    I mean, without rendering, how can I know what is the color at the location of each vertex in a mesh, if there is a material assigned to that mesh?



  • On 02/08/2014 at 06:38, xxxxxxxx wrote:

    Anyone? Please? :-)



  • On 02/08/2014 at 07:07, xxxxxxxx wrote:

    Hi,

    first you will need UVW coordinates for every vertex.
    Then you will need to create proper VolumeData, this is probably most difficult step.

    Then do something like this:

      
    AutoFree<VolumeData> vd(VolumeData::Alloc);  
    // Init VolumeData...  
    ChannelData cd(vd);  
    cd.p = vertices_uvw _;  
    Vector color = shader->Sample(&cd);  
    

    _
    Here is my code that can help Init VolumeData:
    https://github.com/PluginCafe/utilities-and-snippets/blob/master/C%2B%2B/Remo/SamplerRemo.h



  • On 02/08/2014 at 07:43, xxxxxxxx wrote:

    This is my white whale.
    Something I've asked for several times over the span of years. And every single time I've gotten bits and pieces about the UV's. But never enough information to actually do it.

    I wish someone would post a simple working example.
    I've been wanting to know how to do this for years.

    -ScottA



  • On 02/08/2014 at 09:24, xxxxxxxx wrote:

    Hi ScottA and Rui,

    I have updated the code to R15, added some new functionality.
    And finally added new Demo function called

    SampleColorAtVertices()  
    

    If some one find any errors or have any ideas how this can be improved then please let me know.
    I am sure that a lot could be done much better!

    The Code:
    https://github.com/PluginCafe/utilities-and-snippets/tree/master/C%2B%2B/Remo

    regards,
    Remo



  • On 02/08/2014 at 10:13, xxxxxxxx wrote:

    Thanks Remo.

    I'm using R13 and I think Rui is using R14.
    I think I can convert most of it to R13. But what do I use in place of: maxon::BaseArray<Colors> colors;

    Something like this?
    GeDynamicArray<Vector> colors;

    -ScottA



  • On 02/08/2014 at 10:46, xxxxxxxx wrote:

    Please try to not use GeDynamicArray  :)
    Then use std::vector<>  instate.

    Remo



  • On 02/08/2014 at 11:00, xxxxxxxx wrote:

    OK thanks.
    I figured it out after looking closer at your code. I need to use Colors as the type not Vector.

    I think I found a small typo:

    Bool SampleColorAtVertices(BaseObject *obj) //Remo: 02.08.2014  
    {  
      ...code  
      
      ConstUVWHandle uv_handle = uvw_tag->GetDataAddressR();  
      
      //Think it should be this  
      const UVWHandle uv_handle = uvw_tag->GetDataAddressR();  
      
      ..code
    

    -ScottA

    -Edit:
    This is awesome Remo.
    It seems to be working good for me so far in R13. I've been searching for how to this for years.
    Thank you very much!!



  • On 02/08/2014 at 11:24, xxxxxxxx wrote:

    ConstUVWHandle 
    

    This is how it will be done in R15.



  • On 02/08/2014 at 11:27, xxxxxxxx wrote:

    Ah. OK then.
    I still haven't made the Jump to R15 yet. I had to change it in R13 for it to work.

    Thanks again. This is really great.

    -ScottA



  • On 02/08/2014 at 12:27, xxxxxxxx wrote:

    I'm still on vacation but I will get back monday. Can't wait to try it out.
    By the way (and I'm asking this without having seen the code Remo kindly provided), what if the object doesn't have UVW coordinates?



  • On 04/08/2014 at 10:26, xxxxxxxx wrote:

    what if the object doesn't have UVW coordinates?
    Then you can only use 3D Shaders.
    But example code does not support this at this time and will exit with FALSE.
    Another possibility would be to generate some UV and use it.
    From point coordinates for example, or something like this...



  • On 04/08/2014 at 10:32, xxxxxxxx wrote:

    Mmmmmm, so, lets say I have a cube (polygonal) without any UVW tag.
    When I drag a material into it, it gets projected spherically, by default.
    Lets us imagine that is a material with just a bitmap in the color channel.
    Is it possible to sample the color that is at each vertex in this case?
    Or must it be a shader?



  • On 04/08/2014 at 11:20, xxxxxxxx wrote:

    Well then you will need to use ProjectPoint() function that I just added to the code.

    https://github.com/PluginCafe/utilities-and-snippets/blob/master/C++/Remo/SamplerRemo.h

    Not really tested, so if some one find a problem then please let me know.



  • On 04/08/2014 at 11:24, xxxxxxxx wrote:

    I'm just finishing the custom .OBJ output code.
    I will, hopefully, start the color projection code tomorrow. I will let you know how it goes. Very, very much in advance, Remo.



  • On 04/08/2014 at 13:41, xxxxxxxx wrote:

    It's not working for me Remo.
    It works fine in UWV mode. But the other modes are not returning the correct color values.
    I'm still trying to figure out why.

    The trouble seems to be coming from the for() loop under: /// Sample using vertex position and uv.

    -ScottA



  • On 04/08/2014 at 14:08, xxxxxxxx wrote:

    This is probably because no data form TextureTag was used.
    New ReadTextureTag() function may fix this.



  • On 05/08/2014 at 14:11, xxxxxxxx wrote:

    I have changed all the Int32 to LONG, all the FLOAT to float, all the GetInt32 to GetLong, all the GetFloat to GetReal.
    I also had to define PI and PI2
    But now I also stumbled on:

    maxon::BaseArray<Colors> colors;

    I noticed that Scott also stumbled there but from your conversation I could not figure out how to make it work?
    Have you managed to update all the code to R13, Scott? Could your R13 version work on my R14 code?



  • On 05/08/2014 at 14:50, xxxxxxxx wrote:

    I used a GeDynamicArray Rui.
    A Vector is faster. But I prefer to use GeDynamicArray whenever I can so Mac uses can also use my code too. I try to only use Vectors when I need top speed from my arrays. And in this case I don't need a very fast array.
    Most R13 C++ code works in R14 and R15. Which is why I'm still coding in R13.

    I replaced this in Remo's code

        maxon::BaseArray<Colors> colors;  
      colors.Resize(pcnt);
    

    With this R13 compatible code
    Note: Don't forget to put #include "ge_dynamicarray.h" at the top of the code.

    GeDynamicArray<Colors> colors(pcnt);
    

    To print the color results I change Remo's print code to this

        //Print the results   
      for(LONG i=0; i<pcnt; ++i)  
      {  
          //GePrint(RealToString(colors[i].sampled));  
          GePrint("VertID:" +LongToString(i) + " R:" + RealToString(colors[i].col.x) + " G:" + RealToString(colors[i].col.y) + " B:" + RealToString(colors[i].col.z));  
      }
    

    It works fine for UWV mode.
    But I have no idea how to make the new ProjectPoint() stuff work though.
    I have no clue what Remo is doing or talking about with that code.

    -ScottA



  • On 05/08/2014 at 15:20, xxxxxxxx wrote:

    Thank you very much, Scott. It is returning no errors now.
    Now I have to make my code work with it. Still a lot to do.


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