With the following class derived from Model you can draw the infinite world axes as shown in the following image:
The axes are drawn in 3 overridden methods:
DrawViewportBackground: the part of the axes beyond the far plane
DrawViewport: the part between the camera planes
DrawOverlay: the part nearer than the camera near plane
[Update] The code has been improved to support multiple Viewports. Requires Eyeshot 9 >= 9.0.490 or Eyeshot 10 >= 10.0.859
internal class MyModel : Model
{
public Color AxisXColor { get; set; } = Color.Red;
public Color AxisYColor { get; set; } = Color.Green;
public Color AxisZColor { get; set; } = Color.Blue;
// Intersections with the camera planes
Point3D ptXNear, ptXFar, ptYNear, ptYFar, ptZNear, ptZFar;
protected override void DrawViewportBackground(DrawSceneParams data)
{
base.DrawViewportBackground(data);
ComputeNearFarIntersections(data.Viewport);
var rc = data.RenderContext;
rc.PushDepthStencilState();
rc.SetState(depthStencilStateType.DepthTestOff);
rc.SetShader(shaderType.NoLights);
// Draw in 2D the parts of the lines beyond the far camera plane
// X axis
DrawLinesBeyondFar(data.Viewport, ptXNear, ptXFar, AxisXColor);
// Y axis
DrawLinesBeyondFar(data.Viewport, ptYNear, ptYFar, AxisYColor);
// Z axis
DrawLinesBeyondFar(data.Viewport, ptZNear, ptZFar, AxisZColor);
rc.PopDepthStencilState();
}
private void ComputeNearFarIntersections(Viewport viewport)
{
Plane farPlane = viewport.Camera.FarPlane;
Plane nearPlane = viewport.Camera.NearPlane;
Segment3D sX = new Segment3D(0, 0, 0, 1, 0, 0);
Segment3D sY = new Segment3D(0, 0, 0, 0, 1, 0);
Segment3D sZ = new Segment3D(0, 0, 0, 0, 0, 1);
// Compute the intersections with the camera planes
if (!Vector3D.AreParallel(viewport.Camera.ViewNormal, Vector3D.AxisX))
{
sX.IntersectWith(nearPlane, true, out ptXNear);
sX.IntersectWith(farPlane, true, out ptXFar);
if (ptXNear == null)
{
ptXNear = new Point3D(-1e10, 0, 0);
ptXFar = new Point3D(1e10, 0, 0);
}
}
else
{
ptXNear = null;
ptXFar = null;
}
if (!Vector3D.AreParallel(viewport.Camera.ViewNormal, Vector3D.AxisY))
{
sY.IntersectWith(nearPlane, true, out ptYNear);
sY.IntersectWith(farPlane, true, out ptYFar);
if (ptYNear == null)
{
ptYNear = new Point3D(0, -1e10, 0);
ptYFar = new Point3D(0, 1e10, 0);
}
}
else
{
ptYNear = null;
ptYFar = null;
}
if (!Vector3D.AreParallel(viewport.Camera.ViewNormal, Vector3D.AxisZ))
{
sZ.IntersectWith(nearPlane, true, out ptZNear);
sZ.IntersectWith(farPlane, true, out ptZFar);
if (ptZNear == null)
{
ptZNear = new Point3D(0, 0, -1e10);
ptZFar = new Point3D(0, 0, 1e10);
}
}
else
{
ptZNear = null;
ptZFar = null;
}
}
protected override void DrawViewport(DrawSceneParams myParams)
{
base.DrawViewport(myParams);
var rc = myParams.RenderContext;
rc.SetShader(shaderType.NoLights);
// Draw the 3D lines between the camera planes
if (ptXNear != null && ptXFar != null)
{
rc.SetColorWireframe(AxisXColor);
rc.DrawLines(new Point3D[] { ptXNear, ptXFar });
}
if (ptYNear != null && ptYFar != null)
{
rc.SetColorWireframe(AxisYColor);
rc.DrawLines(new Point3D[] { ptYNear, ptYFar });
}
if (ptZNear != null && ptZFar != null)
{
rc.SetColorWireframe(AxisZColor);
rc.DrawLines(new Point3D[] { ptZNear, ptZFar });
}
}
protected override void DrawOverlay(DrawSceneParams data)
{
// Draw in 2D the parts of the lines before the near camera plane
renderContext.SetShader(shaderType.NoLights);
for (int i = 0; i < Viewports.Count; i++)
{
ComputeNearFarIntersections(Viewports[i]);
// X axis
DrawLinesBeforeNear(Viewports[i], ptXNear, ptXFar, AxisXColor);
// Y axis
DrawLinesBeforeNear(Viewports[i], ptYNear, ptYFar, AxisYColor);
// Z axis
DrawLinesBeforeNear(Viewports[i], ptZNear, ptZFar, AxisZColor);
}
}
private void DrawLinesBeyondFar(Viewport viewport, Point3D nearPt, Point3D farPt, Color color)
{
if (farPt == null || nearPt == null)
return;
Vector3D dir = Vector3D.Subtract(farPt, nearPt);
dir.Normalize();
if (viewport == null)
viewport = ActiveViewport;
Point3D pt1 = viewport.WorldToScreen(farPt);
Point3D pt2 = viewport.WorldToScreen(farPt + dir);
DrawLine(viewport, pt1, pt2, color, true);
}
private void DrawLinesBeforeNear(Viewport viewport, Point3D nearPt, Point3D farPt, Color color)
{
if (farPt == null || nearPt == null)
return;
Vector3D dir = Vector3D.Subtract(farPt, nearPt);
dir.Normalize();
if (viewport == null)
viewport = ActiveViewport;
var pt1 = viewport.WorldToScreen(nearPt);
var pt2 = viewport.WorldToScreen(nearPt - dir);
DrawLine(viewport, pt1, pt2, color, false);
}
private void DrawLine(Viewport viewport, Point3D pt1, Point3D pt2, Color color, bool convertToViewport)
{
if (pt1 == null || pt2 == null)
return;
Segment2D screenLine = new Segment2D(pt1, pt2);
int[] viewFrame = viewport.GetViewFrame();
double left = viewFrame[0];
double right = viewFrame[0] + viewFrame[2];
double bottom = viewFrame[1];
double top = viewFrame[1] + viewFrame[3] - 1;
Point2D lowerLeft = new Point2D(left, bottom);
Point2D lowerRight = new Point2D(right, bottom);
Point2D upperLeft = new Point2D(left, top);
Point2D upperRight = new Point2D(right, top);
Segment2D[] screenLines = new Segment2D[]
{
new Segment2D(lowerLeft, lowerRight),
new Segment2D(upperLeft, upperRight),
new Segment2D(lowerLeft, upperLeft),
new Segment2D(lowerRight, upperRight)
};
Point2D ptAxis1 = null, ptAxis2 = null;
Vector2D dir = Vector2D.Subtract(pt2, pt1);
dir.Normalize();
// extend the segment outside the window limits
screenLine.P1 = screenLine.P0 + dir * (viewport.Size.Width + viewport.Size.Height);
// Compute the intersection of the screen line against the lower and upper border of the viewport
Segment2D.Intersection(screenLine, screenLines[0], out ptAxis1);
Segment2D.Intersection(screenLine, screenLines[1], out ptAxis2);
if (ptAxis1 != null)
screenLine.P1 = ptAxis1;
if (ptAxis2 != null)
screenLine.P1 = ptAxis2;
bool clipAgainstVertical = true;
// Compute the intersection of the infinite screen line against the left and right border of the viewport
Segment2D.Intersection(screenLine, screenLines[2], out ptAxis1);
Segment2D.Intersection(screenLine, screenLines[3], out ptAxis2);
if (ptAxis1 != null)
screenLine.P1 = ptAxis1;
if (ptAxis2 != null)
screenLine.P1 = ptAxis2;
renderContext.SetLineSize(1);
renderContext.EnableThickLines();
renderContext.SetColorWireframe(color);
var tol = 1e-6;
// Consider some tolerance
if (screenLine.P0.X >= left - tol && screenLine.P0.X <= right + tol &&
screenLine.P0.Y >= bottom - tol && screenLine.P0.Y <= top + tol &&
screenLine.P1.X >= left - tol && screenLine.P1.X <= right + tol &&
screenLine.P1.Y >= bottom - tol && screenLine.P1.Y <= top + tol)
{
if (convertToViewport)
{
// When drawing the lines beyond far inside the DrawViewportBackground, the camera is set to just the Viewport, not to the whole ViewportLayout,
// so if we have multiple viewports we must adjust the screen coordinates
screenLine.P0 = new Point2D(screenLine.P0.X - left, screenLine.P0.Y - bottom);
screenLine.P1 = new Point2D(screenLine.P1.X - left, screenLine.P1.Y - bottom);
}
renderContext.DrawLines(new float[]
{
(float) screenLine.P0.X, (float) screenLine.P0.Y, 0,
(float) screenLine.P1.X, (float) screenLine.P1.Y, 0
});
}
}
}Previous versions of this article: Eyeshot 12, Eyeshot 8, Eyeshot 7
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