[jitter] plane-to-sphere in a single jit.expr?

HI Joshua, Randy,

Here is the formula as shader vertex code.
Thanks Wes and Marius (but it isn't quite round!)
Get the patch, etc. here:

http://home.earthlink.net/~posit/shader/

cheers

(())_n



// shader es.planesphere.vp.glsl code (())_n

varying vec4 V;
varying vec3 N;
varying vec3 P;
varying vec2 texcoord0;
varying vec2 texdim0;


#define PI 3.141519

uniform float shape;
uniform float delta;

vec3 surface(vec2 point)
{	
	vec2 p; // plane
	p.x = (point.x - 0.5) * 2.;
	p.y = (point.y - 0.5) * -2.;
	vec3 s_point;
	s_point.x = p.x * 1.33;
	s_point.y = p.y;
	s_point.z = 0.;

	vec2 pp; // sphere
	pp.x = (point.x-1.) * -2. * PI;
	pp.y = point.y * PI;
	float acc = sin(pp.y);
	vec3 t_point;
	t_point.x = cos(pp.x-1.57074)*acc;
	t_point.z = sin(pp.x-1.57074)*acc;
	t_point.y = cos(pp.y);

	s_point = mix(s_point,t_point,shape);
	return s_point;
}


void main (void)
{
	vec4 W = vec4( surface(gl_Vertex.xy), 1.);
	
	vec3 neighbour1 = surface(vec2(gl_Vertex.x + delta, gl_Vertex.y));
	vec3 neighbour2 = surface(vec2(gl_Vertex.x, gl_Vertex.y + delta));
	
	vec3 tangent = normalize(neighbour1 - W.xyz);
	vec3 bitangent = normalize(neighbour2 - W.xyz);

	//get the normals into eye space
	N = normalize( cross(tangent, bitangent) );
	N = mat3(	gl_ModelViewMatrixInverseTranspose[0].xyz,
				gl_ModelViewMatrixInverseTranspose[1].xyz,
				gl_ModelViewMatrixInverseTranspose[2].xyz)*N;

	V = vec4(gl_Vertex.xy, 1., 1.);

	texdim0 = vec2 (abs(gl_TextureMatrix[0][0][0]),abs(gl_TextureMatrix 
[0][1][1]));
     texcoord0 = vec2(gl_TextureMatrix[0] * gl_MultiTexCoord0);

	gl_Position = gl_ModelViewProjectionMatrix*W;
}


On Nov 16, 2007, at 2:59 PM, Randy Jones wrote:

>
> Hi Joshua,
>
> the JavaScript from the audiovis_blob example, copied below, should  
> do the trick. The basic expr is in there if you need it.
>
> best,
> Randy
>
>
> On Nov 16, 2007, at 11:30 AM, joshua goldberg wrote:
>
>> i've been trying to figure out jit.expr's ways, and i'm still  
>> smacking my head against the wall a bit.
>>
>> is there a single object jit.expr method of duplicating the plane- 
>> to-sphere method in the jit.gl.render.sphere example patch,  
>> duplicated below?
>
>
>
>
> // viz_poltocar
> //
> // small wrapper for a jit.expr which converts a 1d matrix  
> representing
> // a height field into a 3 plane matrix giving the coordinate of  
> the field
> // wrapped around a sphere.
> //
> // author: rej at 2uptech.com
>
> post ("---plane_to_sphere\n");
> autowatch = 1;
>
> var inputmatrix = new JitterMatrix();
> var outputmatrix = new JitterMatrix();
> var rest_size = 1.;
>
> var myexpr = new JitterObject("jit.expr");
> myexpr.planecount = 3;
> myexpr.type = "float32";
> myexpr.adapt = 1;
> myexpr.interp = 0;
>
> myexpr.expr = ["in[0] * cos((norm[1]-0.5)*PI) * cos((norm[0]-0.5) 
> *TWOPI)",
> 	"in[0] * cos((norm[1]-0.5)*PI) * sin((norm[0]-0.5)*TWOPI)",
> 	"in[0] * sin((norm[1]-0.5)*PI)"];
> 	
> function jit_matrix(inname)
> {
> 	inputmatrix.setinfo(inname);
> 	inputmatrix.frommatrix(inname);
>
> 	outputmatrix.setinfo(inname);
> 	outputmatrix.planecount = 3;
> 	
> 	inputmatrix.op("+", "val", rest_size);
> 	
> 	myexpr.matrixcalc(inputmatrix, outputmatrix);
> 	
> 	outlet(0,"jit_matrix",outputmatrix.name);	
> }
>
>
>
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