I am new to XNA, and I am creating a simple game. Sorry that this is probably really simple, but I can't find any help on it. There is a ship in the game that I made with Blender, and I want to be able to control the ship by being able to rotate the ship's X, Y and Z axises. Here is the code I have:
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
RotationMatrix = Matrix.CreateRotationY(MathHelper.PiOver2) * Matrix.CreateRotationY (rotationY) * Matrix.CreateRotationX(rotationX) * Matrix.CreateRotationZ(rotationZ);
Matrix shipTransformMatrix = RotationMatrix * Matrix.CreateTranslation(ship.Position);
DrawModel(ship.Model, shipTransformMatrix, ship.Transforms);
// TODO: Add your drawing code here
base.Draw(gameTime);
}
public void DrawModel(Model model, Matrix modelTransform, Matrix[] absoluteBoneTransforms)
{
//Draw the model, a model can have multiple meshes, so loop
foreach (ModelMesh mesh in model.Meshes)
{
//This is where the mesh orientation is set
foreach (BasicEffect effect in mesh.Effects)
{
effect.World = absoluteBoneTransforms[mesh.ParentBone.Index] * modelTransform;
effect.Projection = projectionMatrix;
effect.View = viewMatrix;
}
//Draw the mesh, will use the effects set above.
mesh.Draw();
}
}
This will rotate the ship, but not along the ship's axis's. If I rotate the Y axis (by changing the value of rotationY), the ship will rotate along its Y axis. But if I rotate the X or Z axis, the ship rotates according according to the world's X and Z axises, not its own. How do I make it so the ship rotates on its own axises? Do I need to do something different with the matrices? Thanks
Using CreateRotationX, CreateRotationY, & CreateRotationZ all apply rotations around the world or global axes. Meaning it causes your object to rotate only around the world/global axes, not your object's local axes.
Using CreateFromAxisAngle allows you to input whatever rotation axis you want, including the ship's own local axes.
A shift in your overall rotation paradigm will be needed, however, since a rotation around an arbitrary axis like the ship's Up, for instance, can cause a change to any of the 3 angle values at once. Keeping track of all that is unnecessarily difficult. There is an easier way:
Simply store a rotation in matrix (or quaternion) form instead of the 3 angles.
EDIT: Giving some credit here to Steve below (great answer mate, been a while since I did alot of 3D math).
This tutorial here will show you how to setup what Steve suggested!
http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series1/Rotation_-_translation.php
Original Post:
I believe you have to create an effect.Rotation in your BasicEffect loop.
All of this is covered in the basic tutorials over at MSDN I believe. Your code even looks like it came from there.
http://msdn.microsoft.com/en-us/library/bb203897(v=xnagamestudio.31)
If not, check out this link, Reimer covers everything in 3D worth knowing to start:
http://www.riemers.net/eng/Tutorials/XNA/Csharp/series1.php
Here is what I ended up doing just in case anyone else gets stuck like I did:
Matrix RotationMatrix;
//every time I wanted to rotate around an axis, I would do something like this:
protected void rotateY()
{
RotationMatrix *= Matrix.CreateFromAxisAngle(RotationMatrix.Up, MathHelper.ToRadians(1.0f));
//For the X axis I used RotationMatrix.Right, and for the Z RotationMatrix.Forward
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
Matrix shipTransformMatrix = RotationMatrix * Matrix.CreateTranslation(ship.Position);
DrawModel(ship.Model, shipTransformMatrix, ship.Transforms);
// TODO: Add your drawing code here
base.Draw(gameTime);
}
public void DrawModel(Model model, Matrix modelTransform, Matrix[] absoluteBoneTransforms)
{
//Draw the model, a model can have multiple meshes, so loop
foreach (ModelMesh mesh in model.Meshes)
{
//This is where the mesh orientation is set
foreach (BasicEffect effect in mesh.Effects)
{
effect.World = absoluteBoneTransforms[mesh.ParentBone.Index] * modelTransform;
effect.Projection = projectionMatrix;
effect.View = viewMatrix;
}
//Draw the mesh, will use the effects set above.
mesh.Draw();
}
}
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