earthbanana

03-24-2013, 07:16 AM

Okay so this is a pretty specific question having to do with my camera transform in OpenGL. When the view opens the rotation point is around the origin - and when you click on another hexagon tile the rotation point changes to that tiles position. So the transform in pseudo code is -rotationPointTranslationMatrix * rotationMatrix * rotationPointTranslationMatrix.

Well I want the rotation point to change from the origin to the hexagon tile you click without the camera position appearing to change. I would post pictures to show what I'm talking about but I'm new and it won't let me. The problems I am having are strange. So first I also have a camera position - ill call the this transform cameraPositionTranslationMatrix.

All of the tiles are sitting flat along the z=0 plane.

So when I get the transform with this code -

return cameraPositionTranslationMatrix * rotationMatrix * rotationPointTranslationMatrix

it works - the rotation point changes to the correct tile. But the camera position also moves so that the newly selected tile is the center of the screen again. And when I do this...

return cameraPositionTranslationMatrix * -rotationPointTranslationMatrix * rotationMatrix * rotationPointTranslationMatrix

it also works - and now the camera doesn't move and the rotation point changes to the new point exactly like I want. When I rotate the camera it will rotate around that hex tile. However - If I rotate the camera first (for example 30 degrees about the z axis) and then move the point of rotation to another tile - all of the tiles will move in a direction in their coordinate space that is proportional to the angle over the axis. For example - with a 30 degree rotation about the z axis - changing the rotation point from 0,0,0 to 0,10,0 will cause all of the tiles to move a certain amount in their y direction (which makes the camera look like its moving up and to the left).

I can't figure out what in the world is going on here..

I think there must be something wrong with my transformation code - so here it is.

NSMatrix4Df NSMatrix4Df::getRotationMatrix(float xAxisAng, float yAxisAng, float zAxisAng)

{

float xRad = DegreesToRadians(xAxisAng);

float yRad = DegreesToRadians(yAxisAng);

float zRad = DegreesToRadians(zAxisAng);

NSMatrix4Df xRotMat;

NSMatrix4Df yRotMat;

NSMatrix4Df zRotMat;

xRotMat.value(1,1) = cosf(xRad); xRotMat.value(1,2) = -sinf(xRad);

xRotMat.value(2,1) = sinf(xRad); xRotMat.value(2,2) = cosf(xRad);

yRotMat.value(0,0) = cosf(yRad); yRotMat.value(0,2) = -sinf(yRad);

yRotMat.value(2,0) = sinf(yRad); yRotMat.value(2,2) = cosf(yRad);

zRotMat.value(0,0) = cosf(zRad); zRotMat.value(0,1) = -sinf(zRad);

zRotMat.value(1,0) = sinf(zRad); zRotMat.value(1,1) = cosf(zRad);

return zRotMat * yRotMat * xRotMat;

}

NSMatrix4Df NSMatrix4Df::getTranslationMatrix(float xMove, float yMove, float zMove)

{

NSMatrix4Df identity;

// set the fourth column of the matrix to the translation amount

// the rest of the matrix is the identity matrix

identity.setColumn(NSVec4Df(xMove,yMove,zMove,1),3 );

return identity;

}

NSMatrix4Df is just a class to hold a 4x4 matrix in a 2 dimensional array ([4][4]). It is initialized with a 4x4 identity matrix. NSVec4Df is a class that holds a four dimensional vector with x,y,z, and w. Everything is done using floats.

rotationPointTranslationMatrix and cameraPositionTranslationMatrix are filled using the NSMatrix4Df::getTranslationMatrix function and rotationMatrix is filled using NSMatrix4Df::getRotationMatrix - the rotationPoint and position are both a NSVec3Df (same as 4D but no w) in world space coordinates and orientaton is a NSVec3Df with the camera angles around each axis.. (x,y, and z). Please let me know if you see anything wrong with my transformations.. I can't figure out what is going wrong. Any help would be greatly appreciated. Thanks for your time!

Well I want the rotation point to change from the origin to the hexagon tile you click without the camera position appearing to change. I would post pictures to show what I'm talking about but I'm new and it won't let me. The problems I am having are strange. So first I also have a camera position - ill call the this transform cameraPositionTranslationMatrix.

All of the tiles are sitting flat along the z=0 plane.

So when I get the transform with this code -

return cameraPositionTranslationMatrix * rotationMatrix * rotationPointTranslationMatrix

it works - the rotation point changes to the correct tile. But the camera position also moves so that the newly selected tile is the center of the screen again. And when I do this...

return cameraPositionTranslationMatrix * -rotationPointTranslationMatrix * rotationMatrix * rotationPointTranslationMatrix

it also works - and now the camera doesn't move and the rotation point changes to the new point exactly like I want. When I rotate the camera it will rotate around that hex tile. However - If I rotate the camera first (for example 30 degrees about the z axis) and then move the point of rotation to another tile - all of the tiles will move in a direction in their coordinate space that is proportional to the angle over the axis. For example - with a 30 degree rotation about the z axis - changing the rotation point from 0,0,0 to 0,10,0 will cause all of the tiles to move a certain amount in their y direction (which makes the camera look like its moving up and to the left).

I can't figure out what in the world is going on here..

I think there must be something wrong with my transformation code - so here it is.

NSMatrix4Df NSMatrix4Df::getRotationMatrix(float xAxisAng, float yAxisAng, float zAxisAng)

{

float xRad = DegreesToRadians(xAxisAng);

float yRad = DegreesToRadians(yAxisAng);

float zRad = DegreesToRadians(zAxisAng);

NSMatrix4Df xRotMat;

NSMatrix4Df yRotMat;

NSMatrix4Df zRotMat;

xRotMat.value(1,1) = cosf(xRad); xRotMat.value(1,2) = -sinf(xRad);

xRotMat.value(2,1) = sinf(xRad); xRotMat.value(2,2) = cosf(xRad);

yRotMat.value(0,0) = cosf(yRad); yRotMat.value(0,2) = -sinf(yRad);

yRotMat.value(2,0) = sinf(yRad); yRotMat.value(2,2) = cosf(yRad);

zRotMat.value(0,0) = cosf(zRad); zRotMat.value(0,1) = -sinf(zRad);

zRotMat.value(1,0) = sinf(zRad); zRotMat.value(1,1) = cosf(zRad);

return zRotMat * yRotMat * xRotMat;

}

NSMatrix4Df NSMatrix4Df::getTranslationMatrix(float xMove, float yMove, float zMove)

{

NSMatrix4Df identity;

// set the fourth column of the matrix to the translation amount

// the rest of the matrix is the identity matrix

identity.setColumn(NSVec4Df(xMove,yMove,zMove,1),3 );

return identity;

}

NSMatrix4Df is just a class to hold a 4x4 matrix in a 2 dimensional array ([4][4]). It is initialized with a 4x4 identity matrix. NSVec4Df is a class that holds a four dimensional vector with x,y,z, and w. Everything is done using floats.

rotationPointTranslationMatrix and cameraPositionTranslationMatrix are filled using the NSMatrix4Df::getTranslationMatrix function and rotationMatrix is filled using NSMatrix4Df::getRotationMatrix - the rotationPoint and position are both a NSVec3Df (same as 4D but no w) in world space coordinates and orientaton is a NSVec3Df with the camera angles around each axis.. (x,y, and z). Please let me know if you see anything wrong with my transformations.. I can't figure out what is going wrong. Any help would be greatly appreciated. Thanks for your time!