Gaps in seams

[GreatApe]

I've got a problem where two edges join and the vertexes are at different places on the line and I get small gaps in the seam.

http://www.greatape.com/graphics/carseam.gif

It appears to be due to the anti-aliasing effect of the jagged edges of the lines not matching up. Would I be right in thinking this is just one of those problems I have to deal with by making sure vertexes on triangles either side of the join match up?

I'm actually working on OpenGl ES on the symbian emulator if that makes any difference to the issue. Which is one reason I want to avoid adding vertexes as it's going to be running on a low powered device so I want to keep the count as low as possible.

[Hlz]

Looks like a T-junction, alright (discussed in the redbook). The only way I know to eliminate this artifact is to add the vertex, or rely on a particular backround color or geometric situation to hide the problem. If you want generic, high quality results, that may not be a very appealing alternative. Besides, if you're using indexed vertex buffers, the extra vertex count could be marginal. Obviously it all depends on how bad things are, taken as a whole. My suggestion would be to try it and see.

[UrbanLegend]

HI

I would have to agree to Hlz, from your image it looks like you have a T-vert/T-junction problem

Due precision problems if you have a vertext that is placed on a edge, then you going to end up seem a gaps from some angles.

The only way to fix this properly is ensure that you only have vertex to vertex junctions

[GreatApe]

Thanks both, looks like the redbooks something I'm going to have to get stuck into to learn a bit more.

Sure it's not going to cost me too much adding the extra vertices, will just have to bite the bullet and do it.

Use glPolygonOffset?