Re: Problems with planes

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Chikai Ohazama (chikai@talula)
Fri, 21 May 1999 14:25:10 -0700 (PDT)

So I've got some example code for you guys to do what Robert G explained
below. It is a modification to the voglSimple in the Volumizer sample
code. All you need to do is replace the my_DrawVolume with the function
below. Hopefully this is what you guys were talking about.

________________________________________________________________________
Chikai J. Ohazama, Ph.D. SGI
Member of Technical Staff 2011 N. Shoreline Blvd. ms 525
Advanced Graphics Division Mountain View, CA 94043.1389
                                     Telephone: (650) 933-6533
                                     FAX: (650) 964-8671

On Fri, 21 May 1999, Robert Grzeszczuk wrote:

> Ricardo,
>
> Sorry, you still need to specify which indices to use for the polygon (e.g.,
> 0,1,2,3). The easist way to do it is with:
>
> voIndexedFaceSet myFaceSet(4,3,4);
> myFaceSet.appendPoly(myPolygon,4);
>
> or you can set the indices explicitly with set/get methods in the example
> below.
>
> -rg
>
>
> On May 21, 9:48am, Robert Grzeszczuk wrote:
> > Subject: Re: Problems with planes
> > Ricardo,
> >
> > No need to polygonize. You can create your own polygons to be drawn.
> >
> > For example:
> >
> > float myPolygon[] =
> > {
> > 0, 0, 0,
> > 0, 256, 0,
> > 256, 256, 64,
> > 256, 0, 64,
> > };
> >
> > voVertexData *myVertexData = new voVertexData(4,3,myPolygon);
> > voIndexedFaceSet *myFaceSet = new voIndexedFaceSet(myVertexData,4);
>

****************CODE SNIPPET**************************

void my_DrawVolume(
  voIndexedTetraSet * aTetraSet, voBrickSetCollection * aVolume)
{
    int brickNo;
    GLdouble modelMatrix[16], projMatrix[16];

    glGetDoublev(GL_MODELVIEW_MATRIX, modelMatrix);
    glGetDoublev(GL_PROJECTION_MATRIX, projMatrix);

    float myPolygon[] =
    {
        0, 0, 0,
        0, 256, 0,
        256, 256, 64,
        256, 0, 64,
    };

    int BrickCount = aVolume->getCurrentBrickSet()->getBrickCount();
     
    voIndexedFaceSet myFaceSet(4,3,4);
    myFaceSet.appendPoly(myPolygon,4);
  
    // Depth sort the bricks.
    voSortAction aSortAction(
                   aVolume->getCurrentBrickSet(), modelMatrix, projMatrix);

    // Enable 2D or 3D texturing.
    voAppearanceActions::textureEnable(aVolume->getInterpolationType());

    // If no explicit texture coordinates were given, enable texgen().
    if (!hasTextureComponent(interleavedArrayFormat))
      voAppearanceActions::texgenEnable();

/* glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
*/
    glColor4fv(modelColor);

    // prevent Zbuffer fighting among slices
    glDepthMask(GL_FALSE);

    for (brickNo = 0; brickNo < BrickCount; brickNo++) {
        int brickSortedNo = aSortAction[brickNo];
        voBrick *aBrick = aVolume->getCurrentBrickSet()->getBrick(brickSortedNo);

        // Update texgen equation for the current brick.
        if (!hasTextureComponent(interleavedArrayFormat))
          voAppearanceActions::texgenSetEquation(aBrick);
     
        // load the texture from host to texture memory--unless already there
        voAppearanceActions::textureBind(aBrick);
     
        voGeometryActions::draw(
            &myFaceSet,
            interleavedArrayFormat);
    }
}

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