I presume this line:
n = (pos1 -pos0) ^ (pos2 - pos1);
is a cross product of two vectors. i.e. the normal, also known as the
vector perpendicular to the two vectors that define the plane.
In which case you would want to use the glsl function cross(vec3,vec3)
as on the reference sheet I sent previously.
You should have a read about the geometry math being used here. Blindy
copying code without understanding it is a good way to shoot yourself in
the foot later on.
Kim.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Paul
Griffiths
Sent: 27 May 2009 13:40
To: [email protected]
Subject: Re: [osg-users] vertex shader help: compare position against
plane
ok, i got the world position with:
Code:
mat4 ToWorldMatrix= osg_ViewMatrixInverse* gl_ModelViewMatrix;
vec3 worldPos = ToWorldMatrix * gl_Vertex;
now i need to check which side of the plane the worldPos is.
I googled and found some code for this but its not for glsl, ive came up
with this but i get errors.
the code is:
Code:
vec3 n;
float d;
n = (pos1 -pos0) ^ (pos2 - pos1);
d = -n * pos0;
inside = 1.0;
if (dot(n, gl_Position) + w)
{
inside = 0.0;
}
the errors i get are:
Code:
VERTEX glCompileShader "" FAILED
VERTEX Shader "" infolog:
0(46) : error C1021: operands to "^" must be integral
glLinkProgram "eroded" FAILED
Program "eroded" infolog:
Vertex info
-----------
0(46) : error C1021: operands to "^" must be integral
Warning: detected OpenGL error 'invalid operation' after
RenderBin::draw(,)
so i tried
Code:
vec3 n;
float w;
int p0 = (pos1 -pos0);
int p1 = (pos2 - pos1);
n = p0 ^ p1;
w = -n * pos0;
inside = 1.0;
if (dot(n, worldPos) + w)
{
inside = 0.0;
}
but it alway returns inside = 0.0;
any ideas?
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=13031#13031
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