# Slice rotation plan problem

Hello,

I wanted to know if it was possible to slice a plan for example in 2 in Y coordinate and apply a different rotation for each new plan? I managed to almost do that with that code in a vertex shader:

``````
uniform float Angle;

vec4 rotate (vec4 p, float t)
{
if (t<0.5)
{
float	a = smoothstep(0.0, 1.0, Angle * 1.0) * (3.14159 / 2.0);
float	ca = cos(a);
float	sa = sin(a);

return vec4( p.x * sa + p.z * ca,
p.y,
-p.x * ca + p.z * sa,
p.w);
}

else
{
float	a = smoothstep(0.0, 1.0, Angle * 2.0) * (3.14159 / 2.0);
float	ca = cos(a);
float	sa = sin(a);

return vec4( p.x * sa + p.z * ca,
p.y,
-p.x * ca + p.z * sa,
p.w);
}

}

void main()
{
gl_TexCoord[0] = gl_MultiTexCoord0;
vec4 pos          = rotate(gl_Vertex, gl_TexCoord[0].y);
gl_Position       = gl_ModelViewProjectionMatrix * pos;
gl_FrontColor    = gl_Color;

}

``````

And I obtain something like that:

imageshack.us/photo/my-images/7/capturedcran20130408165.png

As you can see the two rectangles are linked and I want to avoid that. It works correctly if I create two rectangles and I apply the shader with different parameters for each but I wanted to know if it was possible to split a plan directly in two and just declare one shader directly and how if you have an idea?

Thanks a lot!

You could do it with a geometry shader by creating 2 rectangles in it.

Ok thanks for the tip but do you think it is possible to do that in avoiding to use the geometry shader and only use the vertex shader?

You canâ€™t create vertices in the vertex shader and you want to split your rectangle which requires creating a vertex

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