Hey!

I need to know how to calculate which Vertex lies in the Frustum and which does not, as I am loading Primitives into the Buffer and do not want to have more than nedded.

My current technique does it like that

 bool inFrustum(Vector3 point,Vector3 relativeCam)
        {
            Vector3 camToPoint = relativeCam - point;
            camToPoint.Normalize();
            lookAt -= camPos;
            lookAt.Normalize();
            float angle = MathHelper.ToDegrees(Math.Abs((float)Math.Acos(Vector3.Dot(lookAt, camToPoint))));
            if (Math.Abs(angle)>50f/2)
                return false;
            else return true;

RelativeCam means it is the Cam relativ to the Center of the Sphere.

It gets the Vektor of the Camera to the Vertex and the Vektor of the Camera where it is pointing to.

Then it calculates the Angle between them and checks if it is inside the 50° (45° + 5° safety).

But I got a big issue. If I go too close to the object (and while itself is rotating) I get positions where no vertex is getting through this function resulting in an empty window for short times.

Is there any better way for calculating this? Or do I have a calculation-mistake?

I tried to use this :

If

distance to middle < -radius

but it won't work at all Oo.

Ah yeah. It was a rather simple approach. As my Farplane and Near-Plane are really long / short (0.01f to 10000000f as it is in Space) i do not care about them.

I have a function, testing if a point is behind another (Z-Buffering) so only half the sphere will be drawn.

The aspect-Ratio is also not that important as I give the Degree of the biggest size ( the width) so the height won't clip that much away but that's okay.

My Problem is, that if the sphere rotates and I am and a close distance, at some degree, the whole sphere disappears and pops up again after rotating on.

If I would check 4 Points of the Frustum Plane, I have another Problem :/

, What if the Cam changes? Z Won't be the Depth anymore and X the Width.

I did pause whenever it blacked out for a moment. And when this happens all the angles are bigger than 50/2

Well it is really confusing when, if the sphere stands still, everything works and it won't disappear compleatly but when the planet is rotating at some angles it disappear.

Thats whats going wrong.

I checked the length of each vertex and they are all almost 1 (because of normalisation) so there can't be an intersection with the nearplane.

I stay the same distance from the sphere but as it rotates it disappears at some angles.

Everything else is finde. At non-Movement it clipps all vertices out that I don't need. (Well it does go for it in a weird way. Somehow..)

Edit: That I tried to.

But there is a problem then. It shows nothing.

The Point is a relative-Point, meaning it is relative to its center. Maybe this is another error

private bool checkForClipping(Quad currentQuad, Vector3 p1, Vector3 p2, Vector3 p3, Vector3 p4)
        {
            Vector3 currentPos = Vector3.Transform(new Vector3(0, 0, 0), world);
            Vector3 relativeCamPos = currentPos - camPos;
            Vector3 rP1 = currentPos - p1; Vector3 rP2 = currentPos - p2;
            Vector3 rP3 = currentPos - p3; Vector3 rP4 = currentPos - p4;
            if(!inFrustum(rP1,relativeCamPos) && !inFrustum(rP2,relativeCamPos) && !inFrustum(rP3,relativeCamPos) && !inFrustum(rP4,relativeCamPos))
            {
                return true;
            }
            rP1.Normalize(); rP2.Normalize(); rP3.Normalize(); rP4.Normalize();
            relativeCamPos.Normalize();
            float angle1 = MathHelper.ToDegrees(Math.Abs((float)Math.Acos(Vector3.Dot(relativeCamPos, rP1))));
            float angle2 = MathHelper.ToDegrees(Math.Abs((float)Math.Acos(Vector3.Dot(relativeCamPos, rP2))));
            float angle3 = MathHelper.ToDegrees(Math.Abs((float)Math.Acos(Vector3.Dot(relativeCamPos, rP3))));
            float angle4 = MathHelper.ToDegrees(Math.Abs((float)Math.Acos(Vector3.Dot(relativeCamPos, rP4))));
            if (angle1 > 95 && angle2 > 95 && angle3 > 95 && angle4 > 95)
            {
                return true;
            }
            
            return false;
        }
        bool inFrustum(Vector3 point, Vector3 relativeCam)
        {
            Vector3 camToPoint = camPos - point;
            camToPoint.Normalize();
            lookAt -= camPos;
            lookAt.Normalize();
            float angle = MathHelper.ToDegrees(Math.Abs((float)Math.Acos(Vector3.Dot(lookAt,camPos))));
            if (angle > 80f / 2)
                return false;
            else return true;
        }

This is the code ATM