How to draw cylinder, again?

[rayn]

Hi, this is newbie question, but I can't get this working for 3 days already.

I need to implement scenenode that draws cylinder and I can't use any mesh file.
My cylinder actually should be N-sided prism with quite big N .
I took CustomSceneNode example and tried to make a prism, with it's base lying in xOy plane and it's sides being parallel to z axis.
So I made following changes:

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class CSampleSceneNode : public scene::ISceneNode
{

	core::aabbox3d<f32> Box;

	irr::core::array<irr::video::S3DVertex> vertex; 
   irr::core::array<unsigned short> index;
	video::SMaterial Material;
	irr::scene::SMeshBuffer mb;


public:
	CSampleSceneNode(scene::ISceneNode* parent, scene::ISceneManager* mgr, s32 id)
		: scene::ISceneNode(parent, mgr, id)
	{	
		int N=5, R=10, H=20;
		//N-number of sides
		//R-radius
		//H-height

		Material.Wireframe = false;
		Material.Lighting = false;
		float baseAngle = 2*core::PI64 / N;

		video::S3DVertex p1,p2;
		float a,b,angle;
		for( int i = 0; i <N+1; i++ )
		{
	       angle = baseAngle * (i+core::PI64/4);

			 a=R*cosf(angle);
			 b=R*sinf(angle);
				
			 p1= irr::video::S3DVertex (a,b,0,0,0,0,video::SColor(255,128,255,255), 0, 0);			 
			 vertex.push_back(p1);		 
			 p2= irr::video::S3DVertex (a,b,H,0,0,0,video::SColor(255,128,255,255), 0, 0);
			 vertex.push_back(p2);
				
		}
		for( int i = 0; i <2*(N+1); i+=1 )
			index.push_back(i);
	}
//...
//same as in example

	virtual void render()
	{
		
		video::IVideoDriver* driver = SceneManager->getVideoDriver();

		driver->setMaterial(Material);
		driver->setTransform(video::ETS_WORLD, AbsoluteTransformation);
		
		driver->drawVertexPrimitiveList(vertex.const_pointer(),vertex.size(), index.const_pointer(), index.size(),video::EVT_STANDARD,scene::EPT_TRIANGLE_STRIP);
			}
//...
//rest same as in example

But that code doesn't work. What I get - are 3 connected planes with a lot of artifacts flying out of planes. It looks like I messed something in index array. But I did it according to TRIANGLE_STRIP definition. Where could be the problem? Could anybody help me, please?

And another question:
If I have the following mesh (thanks vitek for this example):

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  A------------B------------C 
  |          / |\           | 
  |  T1    /   |  \    T4   | 
  |      /     |    \       | 
  |    /       |      \     | 
  |  /   T2    |  T3    \   | 
  |/           |          \ | 
  F------------E------------D 
VertexBuffer = A, B, C, D, E, F 

and if I want to draw it using drawIndexedTriangleList, does it matter in what order I draw triangles?
Will I get different results using

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//                T1         T2         T3         T4 
IndexBuffer =  0, 1, 5,   4, 5, 1,   4, 1, 3,   2, 3, 1 

and

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//                T3       T2         T1           T4 
IndexBuffer =  4, 1, 3, 0, 1, 5,   4, 5, 1,      2, 3, 1 

or using whatever else index buffer if I keep 'winding order'?

[Kriolyth]

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driver->drawVertexPrimitiveList(vertex.const_pointer(),vertex.size(), index.const_pointer(), index.size(),video::EVT_STANDARD,scene::EPT_TRIANGLE_STRIP);

TriangleCount is two less than index.size() in tri-strips, mind that.

Will I get different results using

Code: Select all

//                T1         T2         T3         T4 
IndexBuffer =  0, 1, 5,   4, 5, 1,   4, 1, 3,   2, 3, 1 

and

Code: Select all

//                T3       T2         T1           T4 
IndexBuffer =  4, 1, 3, 0, 1, 5,   4, 5, 1,      2, 3, 1 

or using whatever else index buffer if I keep 'winding order'?

Under most conditions it does not matter. However, if you have ZBuffering off or some fancy alpha blending, you'll get different results if the mesh overlaps itself.

[rayn]

Thanks, Kriolyth.
Now it works. I just miscounted number of indices