Ring mesh buffer

[pera]

I would like to draw 2d circle with thicker line, kind of flat ring in 3d space.
Anyone knows if that as been done?

I've seen this topic http://irrlicht.sourceforge.net/phpBB2/ ... 032#211032 but its just 1 pixel line.

And triangle fans draw full circle, not just outline that i need..

[bitplane]

Since I've been away from Irrlicht for a while and haven't done anything in ages, so I thought I'd have a pop at this.

Here's a screenshot:



The function to create it:

Code: Select all

IMeshBuffer* createRingMesh(f32 radius, f32 width, u32 sections)
{
    CMeshBuffer<S3DVertex>* mb = new CMeshBuffer<S3DVertex>();
    mb->Vertices.set_used(sections*2 + 2); // 2 new verts per section, plus dupe at the start/end
    mb->Indices.set_used(sections*6); // two triangles per section

    // radians per segment
    f32 segRadians = (core::PI*2) / f32(sections);
    f32 segTCoord = 1.0 / f32(sections);

    // position vertices
    for (u32 i=0; i < sections; ++i)
    {
        const vector2df outer = vector2df(sin(segRadians*f32(i)), cos(segRadians*f32(i))) * radius;
        const vector2df inner = vector2df(sin(segRadians*f32(i)), cos(segRadians*f32(i))) * (radius-width);

        S3DVertex &v1 = mb->Vertices[i*2 +0];
        S3DVertex &v2 = mb->Vertices[i*2 +1];
        v1.Color.set(255, 255, 255, 255);
        v1.Normal.set(0, 1.0, 0);
        v1.Pos.set(outer.X, 0, outer.Y);
        v1.TCoords.set(1.0, segTCoord * f32(i));

        v2.Color.set(255,255,255,255);
        v2.Normal.set(0, 1.0, 0);
        v2.Pos.set(inner.X, 0,inner.Y);
        v2.TCoords.set(0.0, segTCoord * f32(i));
    }

    // dupe vertices at the end
    mb->Vertices[sections*2 +0] = mb->Vertices[0];
    mb->Vertices[sections*2 +0].TCoords.set(1.0, 1.0);
    mb->Vertices[sections*2 +1] = mb->Vertices[1];
    mb->Vertices[sections*2 +1].TCoords.set(0.0, 1.0);

    // stitch indices
    u32 v=0;
    for (u32 i=0; i < sections*6; i+=6, v+=2)
    {
        mb->Indices[i+0] = (v+0);
        mb->Indices[i+1] = (v+2);
        mb->Indices[i+2] = (v+3);
        mb->Indices[i+3] = (v+0);
        mb->Indices[i+4] = (v+3);
        mb->Indices[i+5] = (v+1);
    }

    mb->recalculateBoundingBox();
    return mb;
}

And an example of how to use it:

Code: Select all

int main()
{
	IrrlichtDevice *device =
		createDevice( video::EDT_OPENGL, dimension2d<u32>(640, 480), 16,
			false, false, false, 0);

	if (!device)
		return 1;

	IVideoDriver* driver = device->getVideoDriver();
	ISceneManager* smgr = device->getSceneManager();
	IGUIEnvironment* guienv = device->getGUIEnvironment();

    // create ring
    IMeshBuffer* mb = createRingMesh(100.f, 25.f, 15);

    // add it to a mesh and recalculate the bounding box
    SMesh *mesh = new SMesh();
    mesh->addMeshBuffer(mb);
    mesh->recalculateBoundingBox();
    mb->drop();

	IMeshSceneNode* node = smgr->addMeshSceneNode(mesh);

	if (node)
	{
		node->setMaterialFlag(EMF_LIGHTING, false);
		// johnny cash
		node->setMaterialTexture( 0, driver->getTexture("../../media/fire.bmp") );
	}

	smgr->addCameraSceneNodeFPS();

	while(device->run())
	{
		driver->beginScene(true, true, SColor(255,100,101,140));
		smgr->drawAll();
		driver->endScene();
	}

	device->drop();

	return 0;
}

I've moved the topic to the code snippets forum

[ent1ty]

Just curious: Why are you mixing johnny cash and C++ coding?

[bitplane]

Obviously because it's a Ring of Fire.bmp

[hybrid]

Hey bitplane, I guess it's time for a new StandardGeometryMeshFactory Nice to see you here again

[bitplane]

Yeah thats a good idea, but how would it deal with serialization and caching? I have an idea but I'm not sure if you'll like it. I'll start another thread in open discussion about this!

[ent1ty]

Obviously because it's a Ring of Fire.bmp

Ah, didn't realize that, I'm more like rock/metal guy.

[BlindSide]

Just curious: Why are you mixing johnny cash and C++ coding?

I still think this is dangerous. You should be careful when mixing Johnny Cash and C++.

[pera]

Thank you! I owe you one.

This is just what I was looking for. And that bitmap shadow make it look like torus, very nice.

Now let me see how that code works... thats some serious geometry there; when I grow up Im gonna be smart just like you!

[Midnight]

Just curious: Why are you mixing johnny cash and C++ coding?

Why the hell wouldn't you?

[slavik262]

Welcome back Bitplane... us newer members have heard stories about you...

Nice to see you active again.

[Midnight]

are you the same slavik that plays savage by chance?

Here's some johnny to program to, on the house

oh and don't suck bitplane off please. just cause he mobs with the nublets.

[Dorth]

So glad you came back, Midnight, we really missed you.

[Midnight]

So glad you came back, Midnight, we really missed you.

Be nice, play fair.

[pera]

Here is ring o fire in youtube action.