// Draw an ellipse with the specified semi-major axis and eccentricity. The orbit is drawn over a single period,
// fading from full brightness at the given eccentric anomaly.
//
// In order to match exactly the position at which a planet is drawn, the planet's position at the current time
// must be passed as a parameter. positionNow is in the current coordinate system of the render context, not the
// translated and rotated system of the orbital plane.
public static void DrawEllipseWithPosition(RenderContext renderContext, double semiMajorAxis, double eccentricity, double eccentricAnomaly, Color color, Matrix3d worldMatrix, Vector3d positionNow)
{
if (ellipseShader == null)
{
ellipseShader = new EllipseShader();
}
if (ellipseVertexBuffer == null)
{
ellipseVertexBuffer = CreateEllipseVertexBuffer(500);
}
Matrix3d savedWorld = renderContext.World;
renderContext.World = worldMatrix;
renderContext.gl.bindBuffer(GL.ARRAY_BUFFER, ellipseVertexBuffer.VertexBuffer);
renderContext.gl.bindBuffer(GL.ELEMENT_ARRAY_BUFFER, null);
EllipseShader.Use(renderContext, (float)semiMajorAxis, (float)eccentricity, (float)eccentricAnomaly, color, 1.0f, savedWorld, positionNow);
renderContext.gl.drawArrays(GL.LINE_STRIP, 0, ellipseVertexBuffer.Count);
renderContext.World = savedWorld;
}
public static PositionVertexBuffer CreateEllipseVertexBufferWithoutStartPoint(int vertexCount)
{
PositionVertexBuffer vb = new PositionVertexBuffer(vertexCount);
Vector3d[] verts = vb.Lock();
// Setting a non-zero value will prevent the ellipse shader from using the 'head' point
verts[0] = Vector3d.Create(1.0e-6f, 0.0f, 0.0f);
for (int i = 1; i < vertexCount; ++i)
{
verts[i] = Vector3d.Create(2.0f * (float)i / (float)vertexCount, 0.0f, 0.0f);
}
vb.Unlock();
return(vb);
}
public static PositionVertexBuffer CreateEllipseVertexBuffer(int vertexCount)
{
PositionVertexBuffer vb = new PositionVertexBuffer(vertexCount);
Vector3d[] verts = vb.Lock();
int index = 0;
// Pack extra samples into the front of the orbit to avoid obvious segmentation
// when viewed from near the planet or moon.
for (int i = 0; i < vertexCount / 2; ++i)
{
verts[index++] = Vector3d.Create(2.0f * (float)i / (float)vertexCount * 0.05f, 0.0f, 0.0f);
}
for (int i = 0; i < vertexCount / 2; ++i)
{
verts[index++] = Vector3d.Create(2.0f * (float)i / (float)vertexCount * 0.95f + 0.05f, 0.0f, 0.0f);
}
vb.Unlock();
return(vb);
}
void InitLineBuffer(RenderContext renderContext)
{
if (renderContext.gl != null)
{
if (lineBuffers.Count == 0)
{
int count = linePoints.Count;
PositionVertexBuffer lineBuffer = null;
Vector3d[] linePointList = null;
localCenter = new Vector3d();
if (DepthBuffered)
{
// compute the local center..
foreach (Vector3d point in linePoints)
{
localCenter.Add(point);
}
localCenter.X /= count;
localCenter.Y /= count;
localCenter.Z /= count;
}
int countLeft = count;
int index = 0;
int counter = 0;
Vector3d temp;
foreach (Vector3d point in linePoints)
{
if (counter >= 100000 || linePointList == null)
{
if (lineBuffer != null)
{
lineBuffer.Unlock();
}
int thisCount = Math.Min(100000, countLeft);
countLeft -= thisCount;
lineBuffer = new PositionVertexBuffer(thisCount);
linePointList = (Vector3d[])lineBuffer.Lock(); // Lock the buffer (which will return our structs)
lineBuffers.Add(lineBuffer);
lineBufferCounts.Add(thisCount);
counter = 0;
}
if (UseLocalCenters)
{
temp = Vector3d.SubtractVectors(point, localCenter);
linePointList[counter] = temp;
}
else
{
linePointList[counter] = point;
}
index++;
counter++;
}
if (lineBuffer != null)
{
lineBuffer.Unlock();
}
}
}
}
void InitLineBuffer(RenderContext renderContext)
{
if (renderContext.gl != null)
{
if (lineBuffers.Count == 0)
{
int count = linePoints.Count;
PositionVertexBuffer lineBuffer = null;
Vector3d[] linePointList = null;
localCenter = new Vector3d();
if (DepthBuffered)
{
// compute the local center..
foreach (Vector3d point in linePoints)
{
localCenter.Add(point);
}
localCenter.X /= count;
localCenter.Y /= count;
localCenter.Z /= count;
}
int countLeft = count;
int index = 0;
int counter = 0;
Vector3d temp;
foreach (Vector3d point in linePoints)
{
if (counter >= 100000 || linePointList == null)
{
if (lineBuffer != null)
{
lineBuffer.Unlock();
}
int thisCount = Math.Min(100000, countLeft);
countLeft -= thisCount;
lineBuffer = new PositionVertexBuffer(thisCount);
linePointList = (Vector3d[])lineBuffer.Lock(); // Lock the buffer (which will return our structs)
lineBuffers.Add(lineBuffer);
lineBufferCounts.Add(thisCount);
counter = 0;
}
if (UseLocalCenters)
{
temp = Vector3d.SubtractVectors(point, localCenter);
linePointList[counter] = temp;
}
else
{
linePointList[counter] = point;
}
index++;
counter++;
}
if (lineBuffer != null)
{
lineBuffer.Unlock();
}
}
}
}