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#ActualNull_Reference_Exception

Posted 14 December 2013 - 12:37 PM

Maths has never been a strong point of mine.

My problem is that I have a player model thats starts off in the game world and rotates left,right, up, down just fine when stationary. but as soon as the player moves away from the starting position the rotations go all wrong as if the martrixs arent being recalculated. 

 

This is how I am currently calculating the matices in my update method. Any with better maths skills see where the error is?

public void Update(GameTime gameTime)
        {
            KeyboardState keyboardState = Keyboard.GetState();

            float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
                      
            if (keyboardState.IsKeyDown(Keys.Left))
            {                
                shipColBox.AngularVelocity = Vector3.Up;                
            }            

            if (keyboardState.IsKeyDown(Keys.Right))
            {
                shipColBox.AngularVelocity = Vector3.Down;                 
            }

            if (keyboardState.IsKeyDown(Keys.Up))
            {                
                shipColBox.AngularVelocity = Vector3.Left;
            }

            if (keyboardState.IsKeyDown(Keys.Down))
            {
                shipColBox.AngularVelocity = Vector3.Right;
            }            

            // Scale rotation amount to radians per second
            shipColBox.AngularVelocity = shipColBox.AngularVelocity * RotationRate * elapsed;  

            //Create rotation matrix
            Matrix rotationMatrix =
                Matrix.CreateFromAxisAngle(Right, shipColBox.AngularVelocity.Y) *
                Matrix.CreateRotationY(shipColBox.AngularVelocity.X);

            //Rotate orientation vectors
            Direction = Vector3.TransformNormal(Direction, rotationMatrix);
            Up = Vector3.TransformNormal(Up, rotationMatrix);

            // Re-normalize orientation vectors            
            Direction.Normalize();
            Up.Normalize();

            // Re-calculate Right
            right = Vector3.Cross(Direction, Up);
            
            // re-calculate with a cross product to ensure orthagonality
            Up = Vector3.Cross(Right, Direction);

            // Determine thrust amount from input

            if (keyboardState.IsKeyDown(Keys.W))
            {
                thrustAmount = 5.0f;            
            }

            else
            {
                thrustAmount = 0;
                shipColBox.LinearVelocity = new Vector3(0, 0, 0f);
            }

            // Calculate force from thrust amount
            Vector3 force = shipColBox.OrientationMatrix.Forward * thrustAmount * ThrustForce;

            // Apply acceleration
            Vector3 acceleration = force / shipColBox.Mass;
            Velocity += acceleration * elapsed;

            //Apply psuedo drag
            Velocity *= DragFactor;

            //Apply velocity
            shipColBox.Position += Velocity * elapsed;

            // Reconstruct the ship's world matrix
            world = Matrix.Identity;
            world.Forward = Direction;
            world.Up = Up;
            world.Right = right;
            world.Translation = Position;
        }

#2Null_Reference_Exception

Posted 14 December 2013 - 12:36 PM

Maths has never been a strong point of mine.

My problem is that I have a player model thats starts off in the game world amd rotates left,right, up, down just fine when stationary. but as soon as the player moves away from the starting position the rotations go all wrong as if the martrixs arent being recalculated. 

 

This is how I am currently calculating the matices in my update method. Any with better maths skills see where the error is?

public void Update(GameTime gameTime)
        {
            KeyboardState keyboardState = Keyboard.GetState();

            float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
                      
            if (keyboardState.IsKeyDown(Keys.Left))
            {                
                shipColBox.AngularVelocity = Vector3.Up;                
            }            

            if (keyboardState.IsKeyDown(Keys.Right))
            {
                shipColBox.AngularVelocity = Vector3.Down;                 
            }

            if (keyboardState.IsKeyDown(Keys.Up))
            {                
                shipColBox.AngularVelocity = Vector3.Left;
            }

            if (keyboardState.IsKeyDown(Keys.Down))
            {
                shipColBox.AngularVelocity = Vector3.Right;
            }            

            // Scale rotation amount to radians per second
            shipColBox.AngularVelocity = shipColBox.AngularVelocity * RotationRate * elapsed;  

            //Create rotation matrix
            Matrix rotationMatrix =
                Matrix.CreateFromAxisAngle(Right, shipColBox.AngularVelocity.Y) *
                Matrix.CreateRotationY(shipColBox.AngularVelocity.X);

            //Rotate orientation vectors
            Direction = Vector3.TransformNormal(Direction, rotationMatrix);
            Up = Vector3.TransformNormal(Up, rotationMatrix);

            // Re-normalize orientation vectors            
            Direction.Normalize();
            Up.Normalize();

            // Re-calculate Right
            right = Vector3.Cross(Direction, Up);
            
            // re-calculate with a cross product to ensure orthagonality
            Up = Vector3.Cross(Right, Direction);

            // Determine thrust amount from input

            if (keyboardState.IsKeyDown(Keys.W))
            {
                thrustAmount = 5.0f;            
            }

            else
            {
                thrustAmount = 0;
                shipColBox.LinearVelocity = new Vector3(0, 0, 0f);
            }

            // Calculate force from thrust amount
            Vector3 force = shipColBox.OrientationMatrix.Forward * thrustAmount * ThrustForce;

            // Apply acceleration
            Vector3 acceleration = force / shipColBox.Mass;
            Velocity += acceleration * elapsed;

            //Apply psuedo drag
            Velocity *= DragFactor;

            //Apply velocity
            shipColBox.Position += Velocity * elapsed;

            // Reconstruct the ship's world matrix
            world = Matrix.Identity;
            world.Forward = Direction;
            world.Up = Up;
            world.Right = right;
            world.Translation = Position;
        }

#1Null_Reference_Exception

Posted 14 December 2013 - 12:35 PM

Maths has never been a strong point of mine.

My problem is that I have a player model thats starts off in the game world rotates left,right, up, down just fine when stationary. but as soon as the player moves away from the starting position the rotations go all wrong as if the martrixs arent being recalculated. 

 

This is how I am currently calculating the matices in my update method. Any with better maths skills see where the error is?

public void Update(GameTime gameTime)
        {
            KeyboardState keyboardState = Keyboard.GetState();

            float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
                      
            if (keyboardState.IsKeyDown(Keys.Left))
            {                
                shipColBox.AngularVelocity = Vector3.Up;                
            }            

            if (keyboardState.IsKeyDown(Keys.Right))
            {
                shipColBox.AngularVelocity = Vector3.Down;                 
            }

            if (keyboardState.IsKeyDown(Keys.Up))
            {                
                shipColBox.AngularVelocity = Vector3.Left;
            }

            if (keyboardState.IsKeyDown(Keys.Down))
            {
                shipColBox.AngularVelocity = Vector3.Right;
            }            

            // Scale rotation amount to radians per second
            shipColBox.AngularVelocity = shipColBox.AngularVelocity * RotationRate * elapsed;  

            //Create rotation matrix
            Matrix rotationMatrix =
                Matrix.CreateFromAxisAngle(Right, shipColBox.AngularVelocity.Y) *
                Matrix.CreateRotationY(shipColBox.AngularVelocity.X);

            //Rotate orientation vectors
            Direction = Vector3.TransformNormal(Direction, rotationMatrix);
            Up = Vector3.TransformNormal(Up, rotationMatrix);

            // Re-normalize orientation vectors            
            Direction.Normalize();
            Up.Normalize();

            // Re-calculate Right
            right = Vector3.Cross(Direction, Up);
            
            // re-calculate with a cross product to ensure orthagonality
            Up = Vector3.Cross(Right, Direction);

            // Determine thrust amount from input

            if (keyboardState.IsKeyDown(Keys.W))
            {
                thrustAmount = 5.0f;            
            }

            else
            {
                thrustAmount = 0;
                shipColBox.LinearVelocity = new Vector3(0, 0, 0f);
            }

            // Calculate force from thrust amount
            Vector3 force = shipColBox.OrientationMatrix.Forward * thrustAmount * ThrustForce;

            // Apply acceleration
            Vector3 acceleration = force / shipColBox.Mass;
            Velocity += acceleration * elapsed;

            //Apply psuedo drag
            Velocity *= DragFactor;

            //Apply velocity
            shipColBox.Position += Velocity * elapsed;

            // Reconstruct the ship's world matrix
            world = Matrix.Identity;
            world.Forward = Direction;
            world.Up = Up;
            world.Right = right;
            world.Translation = Position;
        }

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