# Transform Matrix and Pivot

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Hello Community,

i have a big Problem, i want to rotate a cube around the Y axis and after it, to move it on the X axis, but the cube still move on the X axis and not in the angle, i had rotated it befor and i don't know what i made wrong, maybe you guys can help me and find a solution?

Here's my code:

Matrix scale = Matrix.Scaling(this.scale);

this.side = Vector3.TransformNormal(Vector3.UnitX, rotation);
this.up = Vector3.TransformNormal(Vector3.UnitY, rotation);
this.look = Vector3.TransformNormal(Vector3.UnitZ, rotation);

Matrix rotation = Matrix.LookAtLH(this.translate, this.pivot.Look, this.pivot.Up);

rotation.M13 = -rotation.M13;
rotation.M31 = -rotation.M31;

Matrix translate = Matrix.Translation(this.translate);

this.world = (scale * rotation * translate);

Greets

Edited by HaloMasterChief

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and after it, to move it on the X axis, but the cube still move on the X axis and not in the angle, i had rotated it befor

What does this mean? "You want to move it on the x axis, but it still moves on the x axis." -> I don't understand.

How is this.translate calculated in your code?

Are you trying to move the object along the X-axis in world space or object space?

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Hello phil_t,

i meant, i want to move the cube on the rotated X axis, not on the origin X axis of the World.

As example what i mean:

And translate, rotate and scale are all Vector3's

Greets

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Then instead of scale -> rotate -> translate, use scale -> translate -> rotate:

this.world = (scale * translate * rotation);

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Hello phil_t,

work's almost perfect, the cube move in the right rotated axis directions, but the only problem is, that the cube rotated around the middle of the scene (0, 0, 0) and not at his self!?

Matrix rotation = Matrix.LookAtLH(this.translate, this.pivot.Look, this.pivot.Up);

or

Matrix rotation = Matrix.LookAtLH(this.translate, this.translate+ this.pivot.Look, this.pivot.Up);

But this dosen't work!?

Matrix scale = Matrix.Scaling(this.scale);

this.side = Vector3.TransformNormal(Vector3.UnitX, rotation);
this.up = Vector3.TransformNormal(Vector3.UnitY, rotation);
this.look = Vector3.TransformNormal(Vector3.UnitZ, rotation);

Matrix rotation = Matrix.LookAtLH(Vector3.Zero, this.pivot.Look, this.pivot.Up);

rotation.M13 = -rotation.M13;
rotation.M31 = -rotation.M31;

Matrix translate = Matrix.Translation(this.translate);

this.world = (scale * translate * rotation );

Greets

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but the only problem is, that the cube rotated around the middle of the scene (0, 0, 0) and not at his self!?

that's cause you translate then rotate.

to rotate around local y , then translate along local x:

start in model space at location 0,0,0 with rotation 0,0,0.  rotate around y.   now calculate the direction of travel. you want to move down local x, which is the direction yr + pi/2   IE the direction you're facing + 90 degrees.

to move:

new x = old x + sin(direction of travel) * speed

new z = old z + cos(direction of travel) * speed

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Hello Norman Barrows,

can you please make a example with my code, because in the Moment i can't understand what i meant?

Greets

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work's almost perfect, the cube move in the right rotated axis directions, but the only problem is, that the cube rotated around the middle of the scene (0, 0, 0) and not at his self!?

Well if you're just placing this cube and that's it, then the end result would be the same.

It sounds like you want to move the cube in the direction after it's already been positioned/rotated, right? Sorry, I didn't understand that at first.

Ok, so go back to what you had before, where world is:

world = scale * rotate * translate;

That's the correct way to assembly your world matrix (scale, rotate, translate).

Now at this point, if you want to move the object along it's local x-axis, each frame you'll want to take the x-axis direction vector and transform it by your rotation matrix:

Vector3 direction = Vector3.TransformNormal(Vector3.UnitX, rotation);

"direction" now points along the local x axis of the rotated cube. So offset your translation in that direction by the desired amount:

this.translate += direction * amountToMove;

and finally calculate your new world matrix:

Matrix translate = Matrix.Translation(this.translate);
this.world = (scale * rotation * translate);
Edited by phil_t

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Hello phil_t,

with the X axis i meant only a example, i want to create a Transform Tool that can place a 3D Object in a Scene where i want, so in the end, I want to move and rotate it on all 3 axis, not only on one axis, how is there the solution?

Greets

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Edit: This is my Code I have:

Matrix scale = Matrix.Scaling(this.scale);

this.localSide = Vector3.TransformNormal(Vector3.UnitX, rotate);
this.localUp = Vector3.TransformNormal(Vector3.UnitY, rotate);
this.localLook = Vector3.TransformNormal(Vector3.UnitZ, rotate);

Matrix translate;

if (transformType == TransformType.Local)
{
this.translate += this.localSide * this.translate.X;
//this.translate += this.pivot.Up * this.translate.Y;
//this.translate += this.pivot.Look * this.translate.Z;

translate = Matrix.Translation(this.translate);
}
else
{
translate = Matrix.Translation(this.translate);
}

this.world = (scale * rotate * translate);
Edited by HaloMasterChief

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