Gradient evaluation outside of render

On 08/05/2015 at 11:31, xxxxxxxx wrote:

User Information:
Cinema 4D Version:   15 
Platform:   Windows  ; Mac  ;  
Language(s) :     C++  ;

It seems the gradient calculate function requires InitRender to be called first.

Is there a way to evaluate CalcGradientPixel without a render structure or is there a way to initialize the render structure without volume data?


On 08/05/2015 at 11:43, xxxxxxxx wrote:

Here is what I tried:

colorGradient = (Gradient* )data->GetCustomDataType( GRADIENTID, CUSTOMDATATYPE_GRADIENT );
InitRenderStruct renderStruct;
renderStruct.Init( bn->GetDocument() );
VolumeData *volumeData = VolumeData::Alloc();
renderStruct.vd = volumeData;
colorGradient->InitRender( renderStruct );

I am confused why this not working.

then try to calculate.


On 09/05/2015 at 02:53, xxxxxxxx wrote:

You don't need no VolumeData for the GradientData. Maybe that is the problem, it works for me with an
empty InitRenderStruct.

On 09/05/2015 at 04:22, xxxxxxxx wrote:

are you initializing that render struct?


On 09/05/2015 at 05:52, xxxxxxxx wrote:

Nope. Here's how it works in Python:

import c4d
def main() :
    gradient = op[c4d.ID_USERDATA,1]
    irs = c4d.modules.render.InitRenderStruct()
    res = gradient.InitRender(irs)
    if res != c4d.INITRENDERRESULT_OK:
        print "InitRender() failed"
        for i in xrange(10) :
            x = i / 9.0
            print gradient.CalcGradientPixel(x)

And I remember successfully doing it in C++ without calling InitRenderStruct::Init().

On 10/05/2015 at 07:25, xxxxxxxx wrote:

I am trying to get this working within an xpresso node.  If I access the gradient directly from the res file it all works fine.  If I access it through a port, it initializes, has the correct render knot count, but crashes on Calc or FreeRender.


On 11/05/2015 at 10:05, xxxxxxxx wrote:


can you tell us what exactly you mean with "working within an xpresso node"? Are you creating your own GvOperatorData plugin?

Best wishes,

On 11/05/2015 at 10:27, xxxxxxxx wrote:

I have created a GvOperatorData plugin.  The problem is that I can not use a port for the gradient successfully.  If I use the res static gradient is all fine.  If I use the port gradient, it will init but crashes when calc or free is called.


On 12/05/2015 at 10:00, xxxxxxxx wrote:


in an Xpresso node, you don't handle parameters but ports. These ports must be handled in special ways:

static Int32 input_ids[] = { GV_TEST_A, GV_TEST_B, 0 };  
GvValuesInfo ports; // data structure for all ports  
// init the input ports  
virtual Bool InitCalculation(GvNode *bn, GvCalc *calc, GvRun *run)  
  return GvBuildValuesTable(bn, ports, calc, run, input_ids);;  
virtual Bool Calculate(GvNode *bn, GvPort *port, GvRun *r, GvCalc *calc)  
  // calculate all ports  
  if (!GvCalculateInValuesTable(bn, r, calc, ports)) return false;  
  // get the "Gradient" port  
  GvPort* portGradient = ports.in_values[0]->GetPort();  
  // get the "Gradient" data  
  Gradient* gradient = nullptr;  
  portGradient->GetDataInstance((const void*&)gradient, CUSTOMDATATYPE_GRADIENT, r);  
  // sample the gradient  
  if(gradient != nullptr)  
      InitRenderStruct irs(bn->GetDocument());  
      for(Int32 i = 0; i < 10; i++)  
          Vector color = gradient->CalcGradientPixel(Float(i) / 10.0);  
  return true;  
// free data  
virtual void FreeCalculation(GvNode *bn, GvCalc *calc)  
  GvFreeValuesTable(bn, ports);  

best wishes,

On 22/05/2015 at 08:55, xxxxxxxx wrote:

Hello Ama,

was your question answered?

Best wishes,