Quad Rendering Issue

Question

I am fairly new to using Quads, so I'm not sure how I can properly describe this issue in all honesty or to even hazard a guess as to why it's happening, so I have a screenshot to illustrate.

So the white lines are actually Quads, the Red lines are just rectangles. So if you can see the issue, for some reason every "now & again" I will get this issue were I get this somewhat looking "dotted line" which will sometimes be a full end-to-end line.

I'm not too sure what's causing this issue, I have a feeling it has something to-do with the way I'm drawing the quads, I don't think it's an incorrect vertices purely because the because of the thickness of the line, this leads me to believe it's the rendering:

effect.CurrentTechnique.Passes[0].Apply();
device.DrawUserPrimitives<VertexPositionColorTexture>(PrimitiveType.TriangleStrip, vertices, 0, totalNumberOfQuads);

This is the order I'm adding the vertices:

1. Top Left Segment Corner
2. Top Right Segment Corner
3. Bottom Left Segment Corner
4. Bottom Right Segment Corner

So after getting the vertices in the correct order, things are now even stranger, as this is an image of the current output:

Here's my Current Code, including the rendering: http://pastebin.com/yK5yBZy0

Answer 1

Keep in mind that the order you insert your vertices into your array matters too. Additionally, it looks like you're drawing a PrimitiveType.TriangleStrip, not quads. It looks like XNA doesn't have a primitive type for quads. You can index them yourself though, as seen in this tutorial..

If you're using triangles (or quads) to draw lines like your image shows, you can have the issue you're experiencing by essentially having a line that has zero height, or close to zero. I imagine this could happen if you're arranging your vertices for quads but then drawing them as triangle strips. So either use the tutorial I mentioned above, or use triangle strips like in this tutorial.

EDIT

The vertices for quads (and triangles) should be defined in clockwise order. Your order is wrong for quads.

You should swap the last two with each other OR the first two with each other, if you want clockwise order. Ensure that you also look at the tutorial I linked. It will describe the proper way to draw the quads.