Hi Tensor,
On Tue, 2004-02-10 at 03:11, Tensor G wrote:
> hello everyone!
>
> i have some little problem understanding the use of colors in opensg, so
> i'll put u several stupid questions, just to get compfy with this stuff...
> I want to assign color values per vertex, so i retrive the meshes
> informations from the scene graph. Then i
> triangleiterate throug the meshes and vertex navigate throug the single
> trinagles...
So far, so well. ;)
> my code looks like:
>
> for every mesh
> for every triangle
> for every vertex
> {
> getvertexinfo (position and normal)
> calculate_color(color_per_vertex)
> push_back_color(color_per_vertex)
> }
>
>
> and then befeore any rendering take place:
>
> for every mesh
> mesh->set_color(color_per_vertex)
>
> but it doesn't work. Now i am thinking that i am wrong parsing the whole
> stuff: i put in the set_color function an explicit color array, with an
> entry for every indexed vertex... now maybe i should simply calculate one
> color for any NON-indexed vertex...
>
> in numbers: if i had a stupid cube with 8 vertices i'd have 36 indices (6
> faces => 12 triangles, 3 vertices per triangle). Now during the color
> assigning, how many colors will i have to pass? 8, one for every vertex, or
> 36, one for every INDEXED-vertex????
> I am confused....
You probably won't get 36, because the cube will probably not replicate
the vertices shared by the two triangles of a side, so I'd more expect
24 (6*4). But in general the question is what you need. If you can live
with using the same index for vertex and color, things are pretty
simple.
> next some pratical questions: how can i know how many triangles and vertices
> are there intoa geoNode?? is there a geoptr->getTriangleNumber() -
> geoptr->getVertexNumber() method???
There is a calcPrimitiveCount() in OSGGeoFunctions.h. But you can also
get the info from the properties.
> If i have to pass a color just for the single color (8 colors for the cube)
> i'd need to know how many vertices i have to create the right amount of
> space in my geoColors3f array....
Yup, you should.
> how can i index my color array in the right way? AKA same index for vertex
> array and color array?
If you're really find with that, it's pretty simple. You just have to
create a Color property with the same size as your vertex property.
The following code snippet does that:
Action::ResultE quitGeo(NodePtr& node)
{
SLOG << "entering " << node << endLog;
GeometryPtr geo = GeometryPtr::dcast(node->getCore());
if(geo!=NullFC)
{
// Add a vertex-unique color to the geometry
GeoPositionsPtr pos = geo->getPositions();
// Create a new Colors property and resize it to have as many
// elements as the positions property.
GeoColors4fPtr colors = GeoColors4f::create();
beginEditCP(colors, GeoColors4f::GeoPropDataFieldMask);
colors->resize(pos->size());
// Traverse the geometry, set the color to the position just for
// testing.
for(TriangleIterator it = geo->beginTriangles();
it != geo->endTriangles(); ++it)
{
colors->getFieldPtr()->setValue(
Color4f( it.getPosition(0)[0],
it.getPosition(0)[1],
it.getPosition(0)[2],
1.f),
it.getPositionIndex(0));
colors->getFieldPtr()->setValue(
Color4f( it.getPosition(1)[0],
it.getPosition(1)[1],
it.getPosition(1)[2],
1.f),
it.getPositionIndex(1));
colors->getFieldPtr()->setValue(
Color4f( it.getPosition(2)[0],
it.getPosition(2)[1],
it.getPosition(2)[2],
1.f),
it.getPositionIndex(2));
}
endEditCP (colors, GeoColors4f::GeoPropDataFieldMask);
// Change the geometry to use the new colors
beginEditCP(geo, Geometry::ColorsFieldMask);
geo->setColors(colors);
// If multi-indexed, make the colors use the same index as
// the geometry
if(geo->getIndexMapping().size() > 0)
{
Int16 pind = geo->calcMappingIndex(Geometry::MapPosition);
if(pind < 0)
{
FFATAL(("Multi-indexed, but no positions index???\n"));
return Action::Continue;
}
// This makes the colors use the same indices as the
positions
geo->getIndexMapping()[pind] |= Geometry::MapColor;
}
endEditCP (geo, Geometry::ColorsFieldMask);
// Check to make sure that the used material actually uses the
// vertex colors
MaterialPtr mat = geo->getMaterial();
SimpleMaterialPtr smat = SimpleMaterialPtr::dcast(mat);
if(smat != NullFC)
{
beginEditCP(smat, SimpleMaterial::ColorMaterialFieldMask);
smat->setColorMaterial(GL_AMBIENT_AND_DIFFUSE);
endEditCP(smat, SimpleMaterial::ColorMaterialFieldMask);
}
else
{
FWARNING(("Material is not simple, can't guarantee "
"color material!\n"));
}
}
return Action::Continue;
}
Hope it helps
Dirk
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