RE: [qwtplot3d-interest] setResolution and Colours

[Dave C. <dm...@ce...>]

Hi Micha,

Thanks for the reply. Got the latest version from CVS this morning but still
had shading issues. I've now modified my source to address the issue,
basically just forced a color lookup for each point of the vertex in the
cell (previously only one color lookup per polygon).

I've pasted the changed function for you, changes are marked with a "//
CHANGED". I assume the non-grid dataview will also need to be changed...

Thanks - and keep up the good work. My plots look fantastic!

Cheers,

Dave.

void
SurfacePlot::updateGridData()
{
   int i, j;
   RGBA col1, col2, col3, col4; // CHANGED
   int cstep = resolution();
   int rstep = resolution();
   if (plotStyle() == FILLEDMESH || plotStyle() == WIREFRAME || plotStyle()
== HIDDENLINE)
   {
      glColor4d(meshColor().r, meshColor().g, meshColor().b, meshColor().a);

      for (i = 0; i < actualGridData_->columns() - cstep; i += cstep)
      {
         for (j = 0; j < actualGridData_->rows() - rstep; j += rstep)
         {
            glBegin(GL_LINE_LOOP);
            glVertex3dv(actualGridData_->vertices[i][j]);
            glVertex3dv(actualGridData_->vertices[i+cstep][j]);
            glVertex3dv(actualGridData_->vertices[i+cstep][j+rstep]);
            glVertex3dv(actualGridData_->vertices[i][j+rstep]);
            glEnd();
         }
      }
   }

   if (plotStyle() != WIREFRAME)
   {
      glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
      glPolygonMode(GL_FRONT_AND_BACK, GL_QUADS);
      glEnable(GL_POLYGON_OFFSET_FILL);
      glPolygonOffset(polygonOffset(),1.0);

      bool hl = (plotStyle() == HIDDENLINE);
      col1 = col2 = col3 = col4 = backgroundRGBAColor(); // CHANGED

      glBegin(GL_QUADS);
      for (i = 0; i < actualGridData_->columns() - cstep; i += cstep)
      {
         for (j = 0; j < actualGridData_->rows() - rstep; j += rstep)
         {
            if(!hl)
            {
               // CHANGED (start)
               col1 = (*dataColor)(
                  actualGridData_->vertices[i][j][0],
                  actualGridData_->vertices[i][j][1],
                  actualGridData_->vertices[i][j][2]);
               col2 = (*dataColor)(
                  actualGridData_->vertices[i+cstep][j][0],
                  actualGridData_->vertices[i+cstep][j][1],
                  actualGridData_->vertices[i+cstep][j][2]);
               col3 = (*dataColor)(
                  actualGridData_->vertices[i+cstep][j+rstep][0],
                  actualGridData_->vertices[i+cstep][j+rstep][1],
                  actualGridData_->vertices[i+cstep][j+rstep][2]);
               col4 = (*dataColor)(
                  actualGridData_->vertices[i][j+rstep][0],
                  actualGridData_->vertices[i][j+rstep][1],
                  actualGridData_->vertices[i][j+rstep][2]);
               // CHANGED (stop)
            }
            glColor4d(col1.r, col1.g, col1.b, col1.a); // CHANGED
            glNormal3dv(actualGridData_->normals[i][j]);
            glVertex3dv(actualGridData_->vertices[i][j]);

            glColor4d(col2.r, col2.g, col2.b, col2.a); // CHANGED
            glNormal3dv(actualGridData_->normals[i+cstep][j]);
            glVertex3dv(actualGridData_->vertices[i+cstep][j]);

            glColor4d(col3.r, col3.g, col3.b, col3.a); // CHANGED
            glNormal3dv(actualGridData_->normals[i+cstep][j+rstep]);
            glVertex3dv(actualGridData_->vertices[i+cstep][j+rstep]);

            glColor4d(col4.r, col4.g, col4.b, col4.a); // CHANGED
            glNormal3dv(actualGridData_->normals[i][j+rstep]);
            glVertex3dv(actualGridData_->vertices[i][j+rstep]);
         }
      }
      glEnd();
      glDisable(GL_POLYGON_OFFSET_FILL);
   }
}

-----Original Message-----
From: Micha Bieber [mailto:kri...@us...]
Sent: Monday, 28 July 2003 6:33 AM
To: Dave Cooper
Cc: qwt...@li...
Subject: Re: [qwtplot3d-interest] setResolution and Colours


Friday, July 25, 2003, 06:58:04, Dave Cooper wrote:

DC> 1. setResolution is excellent for reducing the data. It would be nice if
it
DC> took a double and allowed for increasing the data set (ie. through
spline
DC> interpolation).

Interpolation doesn't increase the dataset per se. It smoothes
(mostly) but the user has to provide sampling points. But you are
right - a conceivable extension to the status quo lies in using of
splines on top of the existing datas. In fact, one reason for me in
writing the library originates from the wish to learn more about
OpenGL. The NURBS and evaluator implementation are still unknown
subjects to me. So, I think to delve into the problem :-)


DC> 2. Colour - I find that a polygon is always entirely filled with the
data
DC> colour of its lowest point. I'd really like to see the colour of the
polygon
DC> shaded over its surface. This is a real problem with small spikes in my
DC> plots.

Fixed (CVS). You should see real Gouraud shading now.


Micha
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