Help with rendering geometries

[shurijo]

I took some code from the forums and tutorial and made the multi-colored triangle work/render fine, but when I tried to change it I couldn't get my shape to render (ps its a hexagon). I'm pretty sure the math is good, I think the issue is with the Indcies.push_back, I really have no idea what that does or how that works.

thanks,

Code: Select all

	
    video::SColor hexColor(255,0,255,255);
    float shortLength = sqrt(segmentLength*segmentLength/2);

    Vertices[0] = video::S3DVertex(centerMapX+shortLength,centerMapY+segmentLength/2,centerMapZ, 0,1,0, hexColor , 0, 1);
    Vertices[1] = video::S3DVertex(centerMapX+shortLength,centerMapY-segmentLength/2,centerMapZ, 0,1,0, hexColor , 0, 1);
    Vertices[2] = video::S3DVertex(centerMapX,centerMapY-segmentLength-shortLength,centerMapZ, 0,1,0, hexColor , 0, 1);
    Vertices[3] = video::S3DVertex(centerMapX-shortLength,centerMapY-segmentLength/2,centerMapZ, 0,1,0, hexColor , 0, 1);
    Vertices[4] = video::S3DVertex(centerMapX-shortLength,centerMapY+shortLength,centerMapZ, 0,1,0, hexColor , 0, 1);
    Vertices[5] = video::S3DVertex(centerMapX,centerMapY+segmentLength+shortLength,centerMapZ, 0,1,0, hexColor , 0, 1);

    core::aabbox3d<f32> Box; 
    Box.reset(Vertices[0].Pos); 
    for (s32 i=1; i<6; ++i) { 
        Box.addInternalPoint(Vertices[i].Pos); 
    } 

    for (s32 i=0; i<6; ++i) { 
        myMeshBuffer->Vertices.push_back(Vertices[i]);         
    } 

    for (s32 i=0; i<6; ++i) { 
        for (s32 j=0; j<6; ++j) { 
            if (i!=j)
                myMeshBuffer->Indices.push_back(j); 
         }
    } 

    myMeshBuffer->BoundingBox = Box; 

    video::SMaterial myMaterial;
    myMaterial.Wireframe = false;
    myMaterial.Lighting = false;

    myMeshBuffer->Material = myMaterial;

[Moni]

Hi shurijo

I'l explain in short what MeshBuffers are and what they are used for, this way you should be able to find the problem in your code yourselfe.

Basically MeshBuffers are used to hold vertices forming meshes. indices are used to define which vertices have to be rendered tougether as a triangle.
lets assume you have a square

0----3
| |
| |
1----2

then the engine will render a triangulation of that square. You'll have to provide that trinagulation for the engine if you create a mesh yourselfe. If you use a meshloader then the loader will take care of that.

let's build that meshbuffer for the square:

first,insert the vertices 0,1,2,3 in that order
mb->Vertices.push_back(vert0);
mb->Vertices.push_back(vert1);
mb->Vertices.push_back(vert2);
mb->Vertices.push_back(vert3);

then you insert the indices which will build the triangulation:
// create triangle 0-1-2
mb->Indices.push_back(0);
mb->Indices.push_back(1);
mb->Indices.push_back(2);
// create triangle 1-2-3
mb->Indices.push_back(1);
mb->Indices.push_back(2);
mb->Indices.push_back(3);

so, for that square you needed 4 vertices and 6 indices

hope that helps
Moni

[deps]

// create triangle 0-1-2
mb->Indices.push_back(0);
mb->Indices.push_back(1);
mb->Indices.push_back(2);
// create triangle 1-2-3
mb->Indices.push_back(1);
mb->Indices.push_back(2);
mb->Indices.push_back(3);

Are you sure it isn't supposed to be like this?

// create triangle 0-1-2
mb->Indices.push_back(0);
mb->Indices.push_back(1);
mb->Indices.push_back(2);
// create triangle 0-2-3
mb->Indices.push_back(0);
mb->Indices.push_back(2);
mb->Indices.push_back(3);

Or am i wrong on this? Never tried this before in irrlicht.

[shurijo]

Hi shurijo

I'l explain in short what MeshBuffers are and what they are used for, this way you should be able to find the problem in your code yourselfe.

hope that helps
Moni

Thanks. I understand everything now. (First time working with meshes and didn't realize that you need to do it like triangles, etc.)

thanks,
-shur