private static VertexBuffer InitializeVertexBuffer()
{
VertexAttribute positions = new VertexAttribute();
positions.Format = VertexElementType.Vector2;
positions.Semantic = VertexAttributeSemantic.Position;
positions.Offset = 0;
return(new VertexBuffer(positions));
}
public static InstancedVertexBuffer CreateInstancedCircle(float radius)
{
List <VertexAttribute> vertexAttributes = new List <VertexAttribute>(1);
List <InstanceAttribute> instanceAttributes = new List <InstanceAttribute>(2);
VertexAttribute positionVertex = new VertexAttribute();
positionVertex.Semantic = VertexAttributeSemantic.Position;
positionVertex.Format = VertexElementType.Vector2;
positionVertex.Offset = 0;
vertexAttributes.Add(positionVertex);
InstanceAttribute positionInstance = new InstanceAttribute();
positionInstance.Semantic = InstanceAttributeSemantic.InstancePosition;
positionInstance.Format = VertexElementType.Vector2;
positionInstance.Offset = 0;
instanceAttributes.Add(positionInstance);
InstanceAttribute colorInstance = new InstanceAttribute();
colorInstance.Semantic = InstanceAttributeSemantic.InstanceColor;
colorInstance.Format = VertexElementType.Vector4;
colorInstance.Offset = 8;
instanceAttributes.Add(colorInstance);
InstancedVertexBuffer ivbo = new InstancedVertexBuffer(vertexAttributes, instanceAttributes);
const int sides = 100;
int floatsPerVertex = 2;
float[] circleData = new float[floatsPerVertex * (sides + 1)];
float theta = 0.0f;
float thetaStep = 2.0f * (float)Math.PI / (sides - 1);
circleData[0] = 0.0f;
circleData[1] = 0.0f;
for (int index = floatsPerVertex; index < circleData.Length; index += floatsPerVertex, theta += thetaStep)
{
circleData[index] = (float)Math.Cos(theta) * radius;
circleData[index + 1] = (float)Math.Sin(theta) * radius;
}
ivbo.SetVertexData(circleData);
return(ivbo);
}
