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uncleF

OpenGL Ray Picking with OpenGL ES on Android

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Hi!

I'm fairly new to the engine side of programming games and have stumble on a problem I can't solve.

I have a working manual ray picking for perspective projection. My problem is with orthographic projection, I can't get it to work. Do you have any code examples?


Thanks
// U

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int glhProjectf(float objx, float objy, float objz, float *modelview, float *projection, int *viewport, float *windowCoordinate)
{
//Transformation vectors
float fTempo[8];
//Modelview transform
fTempo[0]=modelview[0]*objx+modelview[4]*objy+modelview[8]*objz+modelview[12]; //w is always 1
fTempo[1]=modelview[1]*objx+modelview[5]*objy+modelview[9]*objz+modelview[13];
fTempo[2]=modelview[2]*objx+modelview[6]*objy+modelview[10]*objz+modelview[14];
fTempo[3]=modelview[3]*objx+modelview[7]*objy+modelview[11]*objz+modelview[15];
//Projection transform, the final row of projection matrix is always [0 0 -1 0]
//so we optimize for that.
fTempo[4]=projection[0]*fTempo[0]+projection[4]*fTempo[1]+projection[8]*fTempo[2]+projection[12]*fTempo[3];
fTempo[5]=projection[1]*fTempo[0]+projection[5]*fTempo[1]+projection[9]*fTempo[2]+projection[13]*fTempo[3];
fTempo[6]=projection[2]*fTempo[0]+projection[6]*fTempo[1]+projection[10]*fTempo[2]+projection[14]*fTempo[3];
fTempo[7]=-fTempo[2];
//The result normalizes between -1 and 1
if(fTempo[7]==0.0) //The w value
return 0;
fTempo[7]=1.0/fTempo[7];
//Perspective division
fTempo[4]*=fTempo[7];
fTempo[5]*=fTempo[7];
fTempo[6]*=fTempo[7];
//Window coordinates
//Map x, y to range 0-1
windowCoordinate[0]=(fTempo[4]*0.5+0.5)*viewport[2]+viewport[0];
windowCoordinate[1]=(fTempo[5]*0.5+0.5)*viewport[3]+viewport[1];
//This is only correct when glDepthRange(0.0, 1.0)
windowCoordinate[2]=(1.0+fTempo[6])*0.5; //Between 0 and 1
return 1;
}

int glhUnProjectf(float winx, float winy, float winz, float *modelview, float *projection, int *viewport, float *objectCoordinate)
{
//Transformation matrices
float m[16], A[16];
float in[4], out[4];
//Calculation for inverting a matrix, compute projection x modelview
//and store in A[16]
MultiplyMatrices4by4OpenGL_FLOAT(A, projection, modelview);
//Now compute the inverse of matrix A
if(glhInvertMatrixf2(A, m)==0)
return 0;
//Transformation of normalized coordinates between -1 and 1
in[0]=(winx-(float)viewport[0])/(float)viewport[2]*2.0-1.0;
in[1]=(winy-(float)viewport[1])/(float)viewport[3]*2.0-1.0;
in[2]=2.0*winz-1.0;
in[3]=1.0;
//Objects coordinates
MultiplyMatrixByVector4by4OpenGL_FLOAT(out, m, in);
if(out[3]==0.0)
return 0;
out[3]=1.0/out[3];
objectCoordinate[0]=out[0]*out[3];
objectCoordinate[1]=out[1]*out[3];
objectCoordinate[2]=out[2]*out[3];
return 1;
}


http://www.opengl.org/wiki/GluProject_and_gluUnProject_code

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