4 replies to this topic

[James]

Hi all,

I'm writing a simple geometry engine in c++ to work on top of OpenGL. As I began to lay down some code for the 3DObject class I was wondering if anyone had any experience writing one already and could give some ointers or even a sample class definition. e.g. something like the following ....

class C3DObject : CWorldObject
{
public:
C3DObject();
virtual ~C3DObject();

float* m_pfVertices;
unsigned int m_uiNumVertices;

float* m_pfNormals;
unsigned int m_uiNumNormals;

float* m_pfColours;
unsigned int m_uiNumColours;
};

[Ake]

My object class looks alot like yours...
(Somebody please make the code font bigger)

code:

---

    int          m_iNumPolygons;
    CPolygon    *m_cPolygons;
    int          m_iNumVertices;
    CVector     *m_cVertices;
    CVector     *m_cVNormals;
    D3DMATRIX    m_tMatrix;
    CVector      m_cPosition;
    CVector      m_cAngle;
    CTextureCoord *m_cTextureCoords;
    CColor      *m_cVertexColors;
    int          m_iTextureType;
    int          m_iShadingType;

---

I store texturecoords both in the polygons,
and in another array, I use the array when
I do environmentmapping.

Greetings Tobias

[This message has been edited by Ake (edited October 04, 1999).]

[aav]

I have a (for my application) more flexible approach, which is based on a "channel" system. Each Geometry object in my scene is requested every frame to return one or more PrimitiveSet objects. These objects contain various "channels" of per-vertex data:

WSG_XYZ
WSG_COLORn (0-15)
WSG_TEXCOORDn (0-15)
WSG_NORMAL

In addition, the PrimitiveSet has a few functions like ImmediatePrimitive() and
IndexedPrimitive() for specifying TRIANGLES, TRIANGLE_STRIPS, TRIANGLE_FANS etc.

Each PrimitiveSet is bound to a "shader" script, which determines which textures will be used, blending setup between texture layers and what texture coordinate channels to bind the images to. Etc etc.

I find this approach much more flexible than having a fixed class of a "3d" object, as each Geometry-based object has a more "API" based relation to the graphics engine.
YMMV.

[LordChaos]

Using C++ I've found it easier to use vectors
instead of pointer arrays - memory allocation/garbage collection is much easier...

As for the way I've implemented my class, check out my GLobs page

Basically I created an object class which contains vertexbins (ie polygons) and vertex vectors, the polygons using local referencing to get the polygon number..

That's a really bad description....check out the page for more..