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!!ARBvp1.0
# input contains the sphere radius in model coordinates
PARAM sphereRadius = program.env[0];
PARAM half = {0.5, 0.5, 0.0, 2.0 };
PARAM zero = {0.0, 0.0, 0.0, 1.0 };
ATTRIB vertexPosition = vertex.position;
ATTRIB vertexNormal = vertex.normal;
ATTRIB textureCoord = vertex.texcoord;
OUTPUT outputPosition = result.position;
TEMP pos, rad, shf, txt, tip;
# Transform the vertex by the modelview matrix to get into the frame of the camera
DP4 pos.x, state.matrix.modelview.row[0], vertexPosition;
DP4 pos.y, state.matrix.modelview.row[1], vertexPosition;
DP4 pos.z, state.matrix.modelview.row[2], vertexPosition;
DP4 pos.w, state.matrix.modelview.row[3], vertexPosition;
# copy current texture coords
MOV txt.xyzw, textureCoord.xyzw;
# scale the radius by a factor of two
MUL rad.xy, 2.0, sphereRadius.z;
# shift the texture coordinates to the origin
SUB shf.xy, textureCoord, {0.5, 0.5, 0.0, 0.0};
# multiply them to get the vertex offset
MUL shf.xy, rad, shf;
# define the new vertex for corner of sphere
ADD pos.xy, pos, shf;
# apply the projection matrix to get clip coordinates
DP4 outputPosition.x, state.matrix.projection.row[0], pos;
DP4 outputPosition.y, state.matrix.projection.row[1], pos;
DP4 shf.z, state.matrix.projection.row[2], pos;
DP4 shf.w, state.matrix.projection.row[3], pos;
MOV outputPosition.zw, shf;
# compute camera position for front tip of the sphere
ADD pos.z, pos.z, sphereRadius;
# compute Zc and Wc for front tip of the sphere
DP4 tip.z, state.matrix.projection.row[2], pos;
DP4 tip.w, state.matrix.projection.row[3], pos;
# compute 1/Wc for sphere tip
RCP rad.z, tip.w;
# put sphere center Zc into tip.w
MOV tip.w, shf.z;
# compute 1/Wc for sphere center
RCP rad.w, shf.w;
# compute Z/Wc for both sphere tip (->txt.z) and center (->txt.w)
MUL txt.zw, tip, rad;
# move into range 0.0-1.0 to get the normalized depth coordinate (0.5*(Zc/Wc)+0.5)
ADD txt.zw, {0.0,0.0,1.0,1.0}, txt;
MUL txt.zw, {0.0,0.0,0.5,0.5}, txt;
# Pass the color through
MOV result.color, vertex.color;
# Pass texture through
MOV result.texcoord, txt;
END
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