c++ - opengl indexed drawing issue -

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i'm trying render sphere opengl (3.0). algorithm below computes vertices , according indices. in works quite well, however, there seem glitch in matrix, cause ugly cone inside sphere.

enter image description here

vertices.resize(rings * segments * 3); colors.resize(rings * segments * 3); indices.resize(6 * rings * segments);  auto v = vertices.begin(); auto c = colors.begin(); auto = indices.begin();  auto dtheta = m_pi / (f32)rings; auto dphi   = 2 * m_pi / (f32)segments;  ( u32 ring = 0; ring < rings; ++ring ) {     auto r0 = radius * sinf(ring * dtheta);     auto y0 = radius * cosf(ring * dtheta);     ( u32 segment = 0; segment < segments; ++segment ) {         auto x0 = r0 * sinf(segment * dphi);         auto z0 = r0 * cosf(segment * dphi);          *v++ = x0;  *c++ = color.r;         *v++ = y0;  *c++ = color.g;         *v++ = z0;  *c++ = color.b;          if (ring < rings) {             *i++ = ( (ring  ) * segments ) + segment;             *i++ = ( (ring+1) * segments ) + segment;             *i++ = ( (ring+1) * segments ) + segment + 1;             *i++ = ( (ring+1) * segments ) + segment + 1;             *i++ = ( (ring  ) * segments ) + segment + 1;             *i++ = ( (ring  ) * segments ) + segment;         }     } }

any idea i'm missing?

*i++ = ( (ring+1) * segments ) + segment + 1; *i++ = ( (ring+1) * segments ) + segment + 1; *i++ = ( (ring  ) * segments ) + segment + 1;

what index compute if segment equal segments - 1? yes, index next segment.

and if there is no next segment? index outside of list of points.

your segment increment needs wrap around 0:

*i++ = ( (ring+1) * segments ) + (segment + 1) % segments; *i++ = ( (ring+1) * segments ) + (segment + 1) % segments; *i++ = ( (ring  ) * segments ) + (segment + 1) % segments;

also, consider happens if ring equal rings - 1. same problem, need different solution. if statement wrong. should be:

if((ring + 1) < rings)

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