D3DXVECTOR3 X, AbX,Q1,Q2,Q3,Q4; // Vector Variables
float CameraX, CameraY, CameraZ; // temp camera values
g_Camera.GetPosition(CameraX,CameraY,CameraZ); // get camera position
X.x = m_CenterLocation.y - CameraY; // fill X's x value
X.y = CameraX - m_CenterLocation.x; // fill X's y value
X.z = 0.0f; // fill X's z value
// fill in the asbolute values
if(X.x < 0.0f)
AbX.x = X.x * -1;
else
AbX.x = X.x;
if(X.y < 0.0f)
AbX.y = X.y * -1;
else
AbX.y = X.y;
if(X.z < 0.0f)
AbX.z = X.z * -1;
else
AbX.z = X.z;
// fill Quad point 1
Q1.x = m_CenterLocation.x + (m_Width/2)*(X.x/AbX.x);
Q1.y = m_CenterLocation.y + (m_Width/2)*(X.y/AbX.y);
Q1.z = m_CenterLocation.z + (m_Width/2)*(X.z/AbX.z) + (m_Height/2);
// fill Quad point 2
Q2.x = m_CenterLocation.x - (m_Width/2)*(X.x/AbX.x);
Q2.y = m_CenterLocation.y - (m_Width/2)*(X.y/AbX.y);
Q2.z = m_CenterLocation.z - (m_Width/2)*(X.z/AbX.z) + (m_Height/2);
// fill Quad point 3
Q3.x = m_CenterLocation.x - (m_Width/2)*(X.x/AbX.x);
Q3.y = m_CenterLocation.y - (m_Width/2)*(X.y/AbX.y);
Q3.z = m_CenterLocation.z - (m_Width/2)*(X.z/AbX.z) - (m_Height/2);
// fill Quad point 4
Q4.x = m_CenterLocation.x + (m_Width/2)*(X.x/AbX.x);
Q4.y = m_CenterLocation.y + (m_Width/2)*(X.y/AbX.y);
Q4.z = m_CenterLocation.z + (m_Width/2)*(X.z/AbX.z) - (m_Height/2);
Constrained Quad, need some help (complex)
Author
I've been fideling with this for a while, what I'm trying to do is create a custom billboard type Quad in 3D space that pivots on the Z-axis. (Like a fire animation, you walk around and it always faces the camera, but doesn't conform if you look above/below).
The equasion I am using is from the book "Mathematics for 3D Game Programming & Computer Graphics" by Eric Lengyel:
Camera world space point = C, Quad centered at point P, Q1 - Q4 are the coordinates of the quad in counter-clockwise, w is the width, h is the height, and define Vector X as:
X = <Py - Cy,Cx - Px, 0>
Q1 = P + (w/2)(X/|X|) + <0,0,h/2>
Q2 = P - (w/2)(X/|X|) + <0,0,h/2>
Q3 = P - (w/2)(X/|X|) - <0,0,h/2>
Q4 = P + (w/2)(X/|X|) - <0,0,h/2>
So, With this equasion, I wrote the following code:
then I apply the values, however they are totally off (I can't see the quad at all). Did I really goof my code up, did I get the equasion wrong, or am I doing something else?
Thanks!
Off the top of my head, I'd say that you're not interpreting |X| correctly. It's supposed to be the norm of X, which is a scalar computed as follows:
AbX = sqrt( X.x*X.x + X.y*X.y + X.z * X.z)
It's basically the length of the vector.
AbX = sqrt( X.x*X.x + X.y*X.y + X.z * X.z)
It's basically the length of the vector.
Author
You are absoluty right, I'll try that now... for some reason I thought it was asking for the absolute value of the vector.
Author
For the most part it works great now, I have some oddities (such as it is flat at some angles it shouldn't be), but I can at least work from here, you were a great help thanks!
This topic is closed to new replies.
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