Daniela Rainer (zrgr0390++at++visvr1.rus.uni-stuttgart.de)
Mon, 15 Jan 1996 14:37:01 +0000
I have a question about polygons in Performer 2.0:
The direction of the normals of the (GL ?) triangles, that make the
(Performer) polygon are wrong.
For example if I define a rectangle
.........
static pfVec3 coordArray[4] = {
{0.0f, 0.0f, 0.0f},
{1.0f, 0.0f, 0.0f},
{1.0f, 0.0f, 0.5f},
{0.0f, 0.0f, 0.5f}};
static pfVec4 colorArray[4] = {
{1.0f, 0.0f, 0.0f, 1.0f},
{1.0f, 0.0f, 0.0f, 1.0f},
{1.0f, 0.5f, 0.0f, 1.0f},
{0.0f, 0.5f, 0.0f,1.0f}};
static int primLenghthsArray[1]={4};
static pfVec3 normalArray[4]={{0.0f, -1.0f, 0.0f},
{0.0f, -1.0f, 0.0f},
{0.0f, -1.0f, 0.0f},
{0.0f, -1.0f, 0.0f}};
.........
geoset = pfNewGSet(NULL);
pfGSetAttr(geoset,PFGS_COORD3, PFGS_PER_VERTEX, coordArray, NULL);
pfGSetAttr(geoset, PFGS_COLOR4, PFGS_PER_VERTEX, colorArray, NULL);
pfGSetAttr(geoset, PFGS_NORMAL3, PFGS_PER_VERTEX, normalArray, NULL);
pfGSetPrimType(geoset,PFGS_POLYS);
pfGSetNumPrims(geoset, 1);
pfGSetPrimLengths(geoset, primLenghthsArray);
.........
one triangle has the correct normals (0.0f, -1.0f, 0.0f) but the other one
has
(0.0f, 1.0f, 0.0f), so I can't see the whole rectangle but only one triangle.
In wireframe mode I see the correct rectangle.
----------- .
| | . |
| | . |
| | . |
| | . |
----------- ----------
wireframe mode filled polygon
Does anybody know what I am doing wrong here?
Daniela
-- Daniela Rainer rainer++at++rus.uni-stuttgart.de
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