XNA Vertex Buffer is drawing very wrongly - xna

Question

I'm new to using the vertex buffer in XNA. In my project I construct one using a very large amount of vertices. I have been drawing the primitives heretofore with DrawUserIndexedPrimitives(), but I have grown out of that and need more efficiency, so I am trying to figure out the basics of buffers.
I think I've successfully implemented a buffer (and have been very satisfied with the performance improvements), except that all the faces look wrong. Here's how the primitives looked without the buffer: http://i.imgur.com/ygsnB.jpg (the intended look), and here's how they look without: http://i.imgur.com/rQN1p.jpg
Here's my code for loading a vertex buffer and index buffer:
private void RefreshVertexBuffer()
{
List<VertexPositionNormalTexture> vertices = new List<VertexPositionNormalTexture>();
List<int> indices = new List<int>();
//rebuild the vertex list and index list
foreach(var entry in blocks)
{
Block block = entry.Value;
for (int q = 0; q < block.Quads.Count; q++)
{
vertices.AddRange(block.Quads[q].Corners);
int offset = vertices.Count;
foreach (Triangle tri in block.Quads[q].Triangles)
{
indices.Add(tri.Indices[0] + offset);
indices.Add(tri.Indices[1] + offset);
indices.Add(tri.Indices[2] + offset);
}
}
}
vertexBuffer = new DynamicVertexBuffer(graphics, typeof(VertexPositionNormalTexture), vertices.Count, BufferUsage.None);
indexBuffer = new DynamicIndexBuffer(graphics, IndexElementSize.ThirtyTwoBits, indices.Count, BufferUsage.None);
vertexBuffer.SetData<VertexPositionNormalTexture>(vertices.ToArray(), 0, vertices.Count);
indexBuffer.SetData<int>(indices.ToArray(), 0, indices.Count);
}
and here is the draw call for plain rendering:
public void Render(Planet planet, Camera camera)
{
effect.View = camera.View;
effect.Projection = camera.Projection;
effect.World = planet.World;
foreach (KeyValuePair<Vector3, Block> entry in planet.Geometry.Blocks)
{
int blockID = planet.BlockMap.Blocks[entry.Value.U][entry.Value.V][entry.Value.W];
if (blockID == 1)
effect.Texture = dirt;
else if (blockID == 2)
effect.Texture = rock;
effect.CurrentTechnique.Passes[0].Apply();
foreach (Quad quad in entry.Value.Quads)
{
foreach (Triangle tri in quad.Triangles)
{
graphics.DrawUserIndexedPrimitives<VertexPositionNormalTexture>(PrimitiveType.TriangleList,
quad.Corners, 0, quad.Corners.Length, tri.Indices, 0, 1);
}
}
}
}
...and for the vertex buffer rendering:
public void RenderFromBuffer(Planet planet, Camera camera)
{
effect.View = camera.View;
effect.Projection = camera.Projection;
effect.World = planet.World;
graphics.SetVertexBuffer(planet.Geometry.VertexBuffer);
graphics.Indices = planet.Geometry.IndexBuffer;
effect.CurrentTechnique.Passes[0].Apply();
graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, planet.Geometry.VertexBuffer.VertexCount, 0, planet.Geometry.IndexBuffer.IndexCount / 6);
}
My indices may be off? Or is this due to some quirks with how the graphics device acts with a buffer vs. user indexed?
Edit: It may also have something to do with the way I stitch triangle indices. When I built this project with DrawUserIndexedPrimitives, I ran into some issues similar to this where triangles facing a certain direction would draw on the wrong 'side' (or, the wrong face would be culled). So I came up with this solution:
Triangle[] tris;
if (faceDirection == ADJACENT_FACE_NAMES.BOTTOM | faceDirection == ADJACENT_FACE_NAMES.OUTER | faceDirection == ADJACENT_FACE_NAMES.LEFT)
{
//create the triangles for the quad
tris = new Triangle[2]{
new Triangle( //the bottom triangle
new int[3] {
0, //the bottom left corner
1, //the bottom right corner
2 //the top left corner
}),
new Triangle( //the top triangle
new int[3] {
1, //the bottom right corner
3, //the top right corner
2 //the top left corner
})};
}
else
{
tris = new Triangle[2]{
new Triangle(
new int[3] {
2, //the top left corner
1,
0
}),
new Triangle(
new int[3] {
2,
3,
1
})
};
}

Answer 1

The problem is that the triangles are being culled. So you have two options to fix this:
You can change the order of the triangle indices.
foreach (Triangle tri in block.Quads[q].Triangles)
{
indices.Add(tri.Indices[1] + offset);
indices.Add(tri.Indices[0] + offset);
indices.Add(tri.Indices[2] + offset);
}
You can change your RasterizerState...
Default rasterizer state is RasterizerState.CullClockwise...
You can change it to RasterizerState.CullCounterClockwise
EDIT:
this line has a bug:
graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, planet.Geometry.VertexBuffer.VertexCount, 0, planet.Geometry.IndexBuffer.IndexCount / 6)
should be:
graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, planet.Geometry.VertexBuffer.VertexCount, 0, planet.Geometry.IndexBuffer.IndexCount / 3)